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Chapter-2

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CHAPTER-2

REVIEW OF LITERATURE

2.1: ASSOCIATION OF PLANT PARASITIC NEMATODES WITH

ORNAMENTAL PLANTS:

The association of plant parasitic nematodes, their pattern of distribution and

relative dominance has been investigated thoroughly by several workers in different

plants (Sharma and Trivedi, 1994; Ibrahim et al., 2000; Eissa et al., 2009; Sahu et al.,

2011; Srivastava et al., 2012). Moreover, the information on association of plant-

parasitic nematodes on annual and perennial ornamentals, flowering bulbs,

ornamental shrubs, trees and palms in nurseries and gardens is scanty (Ismail and

Eissa, 1993; Bala and Hosein, 1996; Brito et al., 2010; Zarina and Shahina, 2010;

Salawu and Darabidan, 2010; El-Sherbiny, 2011).

One of the earliest records of a nematode fauna of an ornamental plant may be

that of Prillieux (1881) who described nematode disease of hyacinths caused by

Ditylenchus dipsaci (Kuhn) Filipjev. Marcinowski’s classic monograph describes

many nematode/host-plant association including D. dipsaci on hyacinth, phlox and

others, Aphelenchoides sp. on numerous ferns and ornamental plants, and

Meloidogyne sp. on ornamental plants, both glasshouse and outdoor (Marcinowski,

1909). Goff (1936) was one of the first researchers to conduct an extensive survey of

the susceptibility of ornamental plants to Meloidogyne spp. In his survey, Goff noted

the varying degrees of susceptibility among the tested plant species.

Kafi (1963) listed the different nematodes associated with various ornamental

plants. He recorded Aphelenchoides sp., Paratylenchus sp., Tylenchorhynchus sp. and

Xiphinema americanum from the rhizosphere of Chrysanthemum sp.; Aphelenchoides

sp. and Hemicycliophora sp. from the roots of Celosia argentea; Pratylenchus sp.

from the rhizosphere of Hibiscus rosa-sinensis; Ditylenchus sp., Helicotylenchus

dihystera and Tylenchorhynchus sp. from the rhizosphere of Cynodon dactylon and

Pratylenchus coffeae and Rotylenchulus reniformis in the roots of Codiaeum

variegatum. Prasad and Dasgupta (1964) isolated fifteen nematode species from

the rhizosphere of rose. Out of which, Hoplolaimus galeatus, Xiphinema

diversicaudatum, Helicotylenchus nannus, Tylenchorhynchus dubius, Pratylenchus

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pratensis and Hemicycliophora typica were the most frequently encountered species.

The infection of Pratylenchus delattre, M. incognita and Longidorus africanus in the

roots of Crossandra spp. has been reported by Srinivasan and Muthukrishnan (1975),

Rajendran et al. (1976) and Muthukrishnan et al. (1977) respectively.

Sharma (1977) collected 19 soil samples from the different ornamental plants

viz., Anturium sp., Aster amellus, Chrysanthemum sp., Dalhia sp., Gladiolus sp.,

Hemerocallis sp., Paspalum notatum, Portulaca grandiflora, Soyza matrella, Rosa sp

and Urania madgascariensis. He identified 17 genera of plant parasitic nematodes

viz., Aphelenchus avenae, Aphelenchoides ritzemabosi, Boleodorus sp.,

Criconemoides sp., Dolichodorus minor, Helicotylenchus spp., Hemicycliophora spp.,

Meloidogyne spp., Neopsilenchus sp., Pratylenchus sp., Paratylenchus sp.,

Peltamigratus holdemani, Rotylenchulus reniformis, Scutellonema brachyurum,

Tylenchus sp., Tylenchorhynchus acutus and Xiphinema spp. from the surveyed

ornamental plants. He further observed that Helicotylenchus was the predominant

genus with Meloidogyne spp. and Rotylenchulus reniformis being the next.

Krishnappa et al. (1980) conducted a survey on plant parasitic nematodes

associated with ornamental plants in Bangalore. Rotylenchulus reniformis was found

on all plants except Althea rosea, Meloidogyne incognita galls were found on 12

hosts, Helicotylenchus crenatus was found on 10 plants, Tylenchus sp. on 4 plants,

Tylenchorhynchus dubius on 3 plants and Hoplolaimus indicus on only

Chrysanthemum sp. Maqbool et al. (1986) recorded 11 hosts of root-knot nematodes

Meloidogyne spp. (M. incognita Race-1, M. javanica) including ornamentals viz.,

cactus (Opuntia sp.), ceriman (Monstera deliciosa), cock’s comb (Celosia argentea),

dumb cane (Dieffenbachia seguine), milkbush (Euphorbia tirucalli), purslane

(Portulaca oleRacea), red spinach (Amaranthus hybridus) and spider plant

(Chlorophytum cosmosum). Anwar (1989) detected Criconemoides sp., Pratylenchus

sp. and Tylenchorhynchus sp. around the roots of Chrysanthemum sp. and

Aphelenchoides ritzemabosi from the leaf of Chrysanthemum sp. Stephan (1989)

reported Ditylenchus dipsaci on Dianthus caryophyllus and Gladiolus palustris from

Iraq.

Ismail and Eissa (1993) studied the association of plant parasitic nematodes

with ornamental palms in Egypt. The dominant nematode genera reported from the

plants were Criconemoides, Ditylenchus, Helicotylenchus and Rotylenchulus

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reniformis. Marban and Flores (1993) reported the occurrence of Pratylenchus

coffeae, Helicotylenchus californicum, Aphelenchus spp., Tylenchus spp. and

Scutellonema spp. in five varieties of Aglaonema commutatum. Soomro et al. (1993)

reported Amaranthus viridis, Rumex dentatus, Tagetes sp. and Zinnia grandiflora as

host records of M. incognita from Islamabad, Pakistan. Saadabi (1993) revealed the

presence of 12 genera and 13 species of plant parasitic nematodes in both the

rhizosphere soil and roots of ornamental plants. He further pointed out that the M

incognita, Trichodorus sp., Helicotylenchus digonicus, Pratylenchus pratensis,

Hoplolaimus egyptiensis and Tylenchorhynchus maximus may become a limiting

factor in the growth of ornamental plants if not controlled. Ramakrishnan and

Vadivelu (1994) conducted a survey in the chrysanthemum growing areas of

Dharmapuri district, Tamil Nadu. They observed the association of Pratylenchus

penetrans, Meloidogyne incognita, Rotylenchulus reniformis and Helicotylenchus spp.

with the chrysanthemum.

The plant parasitic nematodes viz., Criconema, Hemicycliophora,

Paratylenchus, Helicotylenchus dihystera, Meloidogyne incognita, Tylenchorhynchus

capitatus, Paratylenchus curvitatus, Paratrichodorus minor and Xiphinema krugi

were found to be associated with rose (Rosa sp.), chrysanthemum (Dendranthema

morifolium), carnation (Dianthus sp.), gladiolus (Gladiolus sp.), strelitzia (Strelitzia

reginae), peruvian lily (Alstroemeria sp.) and anthurium (Anthurium sp.). Among

them, Helicotylenchus dihystera, M. incognita and P. penetrans were the most

numerous and widely distributed nematode pests (Petit and Crozzoli, 1995). Jain et al.

(1996) reported the occurrence of Helicotylenchus spp. with some ornamentals. They

found that Helicotylenchus spp. was invariably found associated with most of the

ornamentals viz., china rose (Hibiscus rosa-sinensis), paper flower (Bougainvillea

glabra), Croton (Codiaeum variegatum) and cat’s tail (Acalypha sp.).

Pathak and Siddiqui (1997) conducted a survey to find out the association of

nematodes with some ornamental plants. They observed the presence of

Tylenchorhynchus crotoni in Croton sp., T. ewingi in Rosa sp., T. mashhoodi in

Hibiscus rosa-sinensis, T. brassicae in Nerium odorum, and T. leviterminalis in Rosa

sp. Ismail and Amin (1997) reported the association of plant parasitic nematodes with

cacti and succulent plants in Egypt. They pointed out that the Ditylenchus spp.,

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Helicotylenchus spp., Meloidogyne spp., Rotylenchulus reniformis and

Tylenchorhynchus spp. species were most widely distributed nematodes.

Anitha (1997) reported the presence of Meloidogyne hapla, Helicotylenchus

sp., Pratylenchus sp., Criconemoides sp. and Xiphinema sp. in geranium root and soil

samples collected from Nilgiris area of Tamil Nadu. Khan et al. (1997) reported the

occurrence of Tylenchorhynchus annulatus, Helicotylenchus pseudorobustus, H.

multicinctus, H. indicus, Pratylenchus brachyurus, P. zeae and Hoplolaimus

pararobustus from the rhizosphere of ornamental plants. Pathak et al. (1997) recorded

the occurrence of phytophagous nematodes, associated with soil and roots of woody

ornamental plants (Bougainvillea sp., Clerodendron inerme, Hibiscus rosa-sinensis

and Thuja compacta) for the first time from Bihar.

SoDeuk et al. (1998) revealed that 12 species of plant parasitic nematodes viz.,

Meloidogyne hapla, M. incognita, Pratylenchus penetrans, Tylenchorhynchus

claytoni, T. nudus, Helicotylenchus pseudorobustus, Criconemoides morgensis,

Ditylenchus dipsaci, Discocriconemella hengsungica, Hemicycliophora koreana,

Xiphinema pini and Aphelenchus avenae were associated with the rhizosphere of

peony plants. Frequency and density of these nematodes varied in different regions.

Meloidogyne hapla was found to be the most frequent and prevalent in all the regions

surveyed, whereas, high frequency and density of C. morgensis, D. hengsungica and

H. koreana was recorded in hilly regions.

Al-Yahya et al. (1999) found that root-knot nematode, Meloidogyne javanica

was found attacking ornamental plants viz., Bougainvillea sp., Catharanthus roseus,

Cotoneaster sp., Dianthus caryphyollus, Dodonia viscose, Gomphrena globosa, Rosa

sp., and Verbena hybrida. Rotylenchulus sp. was found with high density in the

rhizosphere soil samples of Tecoma stans and Dodonaea viscosa. Pin nematode,

Paratylenchus sp. was recorded in highest population density on Codiaeum sp., and

also caused severe damage to the infected plant. Zeng et al. (2000) identified three

species of root-knot nematode viz., M. arenaria, M. javanica and M. incognita

infecting ornamental plants in China namely Lantana camara, Euphorbia

cochininchensis, and Coleus pumilus.

Johnson et al. (2002) reported the association of plant parasitic nematodes viz.,

Meloidogyne spp., Pratylenchus coffeae, Tylenchorhynchus nanus, Helicotylenchus

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multicinctus, Xiphinema basiri and Longidorus elongatus with gerbera and asiatic lily.

They also indicated the importance of M. incognita and P. coffeae in causing major

production constraints in gerbera and asiatic lily. Ismail et al. (2002 and 2004)

conducted a survey for the occurrence and distribution of plant parasitic nematodes in

chamomile (Matricaria recutita L.) and jasmine (Jasminum grandiflorum L.). In their

survey they revealed the presence of Tylenchorhynchus spp., Tylenchus spp.,

Pratylenchus spp., and Meloidogyne spp. as the major nematode pests on chamomile.

Whereas, Rotylenchulus reniformis, Helicotylenchus spp., Tylenchorhynchus spp. and

Meloidogyne spp. were the major nematode pests on jasmine.

Aziz et al. (2003) studied the diversity as well as population dynamics of

phytoparasitic nematodes associated with some ornamental plants growing in the

campus of Aligarh Muslim University, Aligarh, India. The nematodes detected in soil

samples collected from ornamental plants were Aphelenchoides sp., Criconemoides

sp., Helicotylenchus sp., Hoplolaimus sp., Longidorus sp., Meloidogyne sp.,

Pratylenchus sp., Tylenchorhynchus sp., and Xiphinema sp. Frequency and

diversification of Hoplolaimus sp., Helicotylenchus sp., Criconemoides sp. and larvae

of Meloidogyne sp. were quite high. The nematodes Aphelenchoides sp.,

Tylenchorhynchus sp., Xiphinema sp. and Longidorus sp. were less frequently

observed and had lowest diversity. The diversity of the remaining 2 nematodes was in

the medium range. Relative density of Rotylenchulus sp. on Antirrhinum majus was

lowest and that of Meloidogyne spp. on Petunia alba was highest. The absolute

frequency of Tylenchorhynchus sp. was very low and that of Meloidogyne sp. was

very high. A few nematodes like Hoplolaimus sp., Helicotylenchus sp., Pratylenchus

sp., Rotylenchulus sp. and Meloidogyne larvae were also observed in the root tissues.

Singh et al. (2003) described three new species of Hemicriconemoides viz., H. rosae,

H. rotundus and H. asymmetricus from the rhizosphere of Rosa indica and Hibiscus

rosa-sinensis in Bareilly district of U.P., India.

Abelleira et al. (2004) carried out a survey in some public parks and gardens

to determine the presence of plant pathogenic soil nematodes in Camellia japonica.

Nine genera of phytopathogenic nematodes were found to be associated with C.

japonica. The nematodes detected were Hemicriconemoides spp., Macrophostonia

spp., Pratylenchus spp., Helicotylenchus, Rotylenchus spp., Meloidogyne spp.,

Xiphinema, Trichodorus and Paratrichodorus.

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Shahina and Musarrat (2006) reported that the roots of ornamental plants viz.,

Duranta repens, Bassia scoparia, Ficus benjamina, Pedilanthus tithymaloides and

Sansevieria trifasciata were found infected with Meloidogyne incognita and

Rotylenchulus reniformis. These plants were also showing the symptoms of yellowing

of leaves and stunted growth as compared to healthy plants. Singh and Tyagi (2007)

revealed a number of plant parasitic nematodes associated with sun flower. Out of

which reniform nematode, R. reniformis was found in greater number. Under field

conditions, yellowing, stunting and reduction of sunflower bolls have also been

observed. Other nematodes like root-knot, spiral, stunt and lance were also recorded

in the soil samples collected in the three states.

Oliveira and Kubo (2007) reported that the most frequently occurring plant

parasitic nematodes in ornamental plants in Brazil were M. javanica (38%), M.

incognita (19%) and Helicotylenchus dihystera (11%). They further recorded some

new hosts of plant parasitic nematodes viz., M. incognita in Gloxinia sp., Arundina

graminifolia and Aptenia cordifolia; M. javanica in Arundina graminifolia, Hibiscus

spp., Gloxinia sp., Eustoma grandiflorum, Heliconia rostrata, Graptophyllum pictum,

Holmskioldia sanguine and Exacum affine; Pratylenchus brachyurus in Eustoma

grandiflorum, Cattleya sp. and different cultivars of Lilium sp.; Helicotylenchus

dihystera in Eustoma grandiflorum, Lilium sp., Impatiens balsamina and Aptenia

cordifolia; Helicotylenchus multicinctus in Pachystachys lutea; Helicotylenchus

pseudorobustus in Heliconia sp.; and Cactodera cacti in Schlumbergera species.

Dias-Arieira et al. (2007) recorded highest nematode density of Meloidogyne in

Zoysia japonica and Helicotylenchus in Schlumbergera truncata and Hemerocallis

flava. The Helicotylenchus spp. were the most frequently isolated, followed by

Tylenchus spp., Meloidogyne and Paratylenchus spp., Mesocriconema, tricodorideous

nematodes and Pratylenchus spp. However, Rotylenchulus, Xiphinema, Aorolaimus

and Hoplolaimus occurred in low frequencies.

Deimi et al. (2008) conducted a survey of ten flowering ornamental plants viz.,

calla lily (Zantedeschia aethiopica (L.) K. Spreng.), carnation (Dianthus caryophyllus

L.), chrysanthemum (Dendranthema grandiflorum Kitam. cv. Puja), iris (Iris

versicolor L.), gladiolus (Gladiolus grandiflorus L.), rose (Rosa foetida J. Herrm.),

snapdragon (Antirrhinum majus L.), stock (Matthiola incana L.R. Br), tuberose

(Polianthes tuberosa L.) and tulip (Tulipa gesneriana L.). They reported twenty one

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nematode species viz., Aphelenchus avenae, Aphelenchoides subtenuis, Boleodorus

thylactus, Ditylenchus kheirii, D. myceliophagus, Filenchus sandneri, Helicotylenchus

crassatus, H. crenacauda, H. digonicus, H. pseudodigonicus, H. pseudorobustus, H.

vulgaris, Irantylenchus vicinus, Merlinius brevidens, Paratylenchus similis, P.

neglectus, P. penetrans, P. thornei, Tylenchorhynchus dubius, T. canalis and

Zygotylenchus guevarai associated with these ornamental plants. They further noted

that nematode species varied in their frequency of distribution amongst all ten plant

species.

Abbas and Waliullah (2010) reported that among plant parasitic nematodes,

Meloidogyne, Helicotylenchus and Pratylenchus spp. were found to be associated

with the roots of gladiolus. Analysis of nematode community of three localities viz.,

Cheshmashahi, Shalimar and Chandpora of Srinagar district of Kashmir Valley

revealed that H. pseudorobustus and Basiria graminophila were predominant at

Cheshmashahi, while, B. graminophila and Xiphinema basiri at Shalimar and B.

graminophila and Pratylenchus spp. at Chandpora. The Rhabditids and some other

free living nematodes were also found in all the three localities in varying numbers.

Seenivasan (2010) recorded eight genera of plant parasitic nematodes viz.,

Hoplolaimus indicus, Helicotylenchus dihystera, Longidorus sp., Meloidogyne

incognita, Pratylenchus delattrei, Radopholus similis, Tylenchorhynchus nudus and

Xiphinema insigni associated with rhizosphere of jasmine, growing in different

districts of Tamil Nadu. Among the plant parasitic nematodes M. incognita and P.

delattrei were frequently encountered nematodes with higher relative density and

prominence value. Zarina and Shahina (2010) conducted a survey of two cultivated

ornamental plants, butterfly pea (Clitoria ternatea L.) and motia (Jasminum sambac

(L.) Aiton) for the presence of plant parasitic nematodes. They revealed that the two

species of Meloidogyne viz., M. incognita and M. javanica were infecting these two

ornamental plants. Brito et al. (2010) examined 206 root samples from ornamental

plants growing in ornamental nurseries and various landscapes. They observed that

six Meloidogyne spp. viz., M. arenaria, M. floridensis, M. graminis, M. incognita, M.

javanica and M. mayaguensis were infecting ornamental plants.

EL-Sherbiny (2011) reported that the Meloidogyne, Rotylenchulus,

Tylenchorhynchus, Aphelenchus and Zygotylenchus were most frequent and/or

prominent genera found associated with the ornamentals, whereas, Trichodorus,

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Xiphinema and Longidorus were the least ones. Roots of Albizia lebbeck, Cordia

myxa, Ficus religiosa, Pithecellobium dulce, Pongamia pinnata, Prosopis juliflora,

Sterculia diversifolia, Vitex agnus-castus, V. trifolia, V. trifolia variegata and

Washingtonia robusta were found infected with M. incognita. Similarly, the infection

of M. javanica was observed on the roots of Callistemon viminalis, Carissa

macrocarpa, Chamaerops humilis, Duranta repens, Eremophila bowmanii, Melia

azedarach, Phoenix canariensis, Sabal palmetto and Zizphus spina-christi. The

concomitant infection of M. arenaria and M. javanica was also found on the roots of

Hibiscus tiliaceus. Numerous young and adult females of the reniform nematode, R.

reniformis were found attached to the roots of Parkinsonia aculeata. Similarly, Khan

and Ghosh (2011) isolated the M. incognita, Hoplolaimus indicus, Helicotylenchus

multicinctus, Tylenchorhynchus mashhoodi, R. reniformis, Criconemoides onoensis,

Pratylenchus zeae and Mylonchulus spp. from the rhizosphere of tuberose. They also

recovered A. besseyi from infested flowers of tuberose.

2.2: PATHOGENICITY OF ROOT-KNOT NEMATODES:

Plants provide an excellent ecosystem for microorganisms that interact with

plant cells and tissues with different degrees of dependence. Many pathological

effects due to nematode infection include hypertrophy and hyperplasia of

parenchymatous cells, suppressed cellular division, root pruning and root

proliferation. Nematodes cause lesions, discolouration, deformity and in some cases,

complete devastation in the penetration and feeding areas. They also cause decline,

and in extreme cases, death of the plant. The size and quality of fruits, ornamentals

and vegetables are reduced. Plants under attack by nematodes lose vigour and become

unthrifty. All these effects vary with the nematode, host plant and other organisms

present. In general nematode infection results in stunted plant growth, lower yields

and reduced quality of most crops and lower returns to the farmer.

However, the mere presence of plant-parasitic nematodes in soil does not

guarantee crop damage or yield loss, since a nematode population may remain below

the damage threshold level for a specific period (Brown, 1987; Schomaker and Been,

2006). It is established that increasing nematode population densities can

progressively decrease crop performance and there is minimal threshold density,

below which no measurable loss in yield occurs. Factors such as environmental

conditions, soil type, previous cropping history, the specific nematode species and

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(or) race present, pathotype distribution, prevailing nematode distribution pattern,

nematode multiplication rate, and plant cultivar that is grown will all have a bearing

on whether crop damage and yield reduction will be inflicted (Brown, 1987;

Schomaker and Been, 2006; Khan, 2008). Knowledge of relevant principles and

determination of damage functions under specific conditions for specific crops are

prerequisites for the estimation of nematode economic threshold values and are

essential for nematode pest management programmes (Ferris, 1978; Schomaker and

Been, 2006).

Sharma and Sethi (1975) reported that 100 larvae of M. incognita per 500g of

soil was the marginal threshold level for producing measurable effects on the growth

of cowpea. The host infestation and nematode multiplication were found to be density

dependent. The final population was maximum at an initial inoculum level of 100

larvae but the rate of multiplication was highest where in 10 larvae were used.

Rajendran et al. (1976) conducted an experiment using a series of 10, 100, 1000,

2000, 5000 and 10000 second stage juveniles of M. incognita. They reported that

there was significant difference in the plant growth between M. incognita inoculated

and un-inoculated Crossandra undulaefolia S. plants. The inoculated plants exhibited

retardation in shoot growth, with smaller chlorotic leaves almost turning to white in

advanced stages of infestation. Those which received initial inoculums of 1000, 2000,

5000 and 10000 nematode larvae were more seriously affected.

Caveness and Wilson (1977) observed that M. incognita and M. javanica

readily attacked Celosia argentea and significantly reduced its early, rapid growth.

They observed that at harvest, all plants grown in root-knot infested soil were

significantly smaller than plants grown in fumigated soil and roots were heavily

galled, indicating that this cultivar was highly susceptible to the nematodes. Nath et

al. (1979) found that the root and shoot growth and pod number of chickpea plants

decreased with increasing inoculum density. Flowering was delayed by 10 to 15 days

following inoculation with 1000 or more juveniles of M. incognita and at a density of

1000,00 nematodes, the seedlings failed to flower. Mortality of seedling was

minimum at the highest inoculum density of 1000,00 juveniles after 30 days. The

pathogenic threshold level was 1000 juveniles/500 g soil.

Mani and Sethi (1984) determined the pathogenicity of M. incognita on

chickpea cv. Pusa 209, using five inoculum levels, viz., 0.5, 1.0, 2.0, 4.0 and 8.0

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larvae per gram of soil. There was a progressive decrease in plant growth as the

inoculum level of nematode increased. An inoculum of 2 larvae per gram soil was

found to be damaging threshold level of M. incognita on chickpea. Sundrababu and

Vadivelu (1985) tested the pathogenicity of M. incognita, M. javanica and M.

arenaria on Polyanthus tuberosa separately by inoculating 2 larvae per gram soil of

each species in pots containing sprouted tuberose bulbs. Their results indicated that

M. incognita and M. arenaria were more pathogenic to tuberose than M. javanica.

Patnaik and Das (1986) noted the damage threshold level of coleus (Coleus

parviflorus) as 10 juveniles of M. incognita per 3 kg soil. As this inoculum level was

sufficient to induce gall formation. But, the significant reduction in tuber yield was

observed at100 nematodes/pot and onwards with maximum reduction in tuber yield at

1000 nematodes/pot. Dry weight of roots increased (except for 10 nematodes /pot)

with an increase in inoculum level upto 1000 nematodes/pot, while in case of shoots,

there was a downward trend. Dhankar et al. (1986) found threshold inoculum level of

M. incognita on water melon (Citrullus vulgaris Scharad) as 1000 larvae/kg soil, at

this inoculum level all the plant growth parameters were significantly reduced over

control. At 10 larvae/kg soil, there was stimulatory effect with extensive root

proliferation. The plants exhibited stunted growth, yellowing and drooping of leaves

and even premature death at an inoculum level of 10,000 larvae/kg soi.

Acharya and Padhi (1987) reported significant reductions in betelvine plant

growth, particularly shoot and root length, dry weight of shoot and root at different

inoculum levels of M. incognita. They reported 100 larvae per 1.5 kg soil as the

damage threshold level of betelvine. At this level, symptoms like thinly spread foliage

with small leaves, yellowing and premature shedding of leaves and also stunting of

plant were recorded. The final nematode population increased significantly with

increase in initial inoculum levels.

Haseeb and Butool (1989) reported that root-knot nematode, M. incognita

severely limited the growth and oil yield of Ocimum sanctum L. They noticed that

with increase in the initial inoculum level, there was a corresponding decrease in root-

shoot length, fresh and dry weight of plants and total oil yield. Intensity of host

reaction in terms of root galling was directly proportional to the increase in the initial

inoculum level. The highest rate of reproduction was observed at lowest inoculum

level, whereas, the lowest rate of reproduction was observed at highest inoculum

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level. Amaranatha and Krishnappa (1989) studied the effect of different inoculum

levels of M. incognita on sunflower and recorded that as the population density of

nematodes increased, plant growth decreased. They also showed that inoculation of

10,000 juveniles of M. incognita per plant proved to be the damage threshold level

and plants at this level exhibited stunting, yellowing and drooping of leaves.

Pankaj and Siyanand (1990) studied the effect of initial inoculum levels viz., 0,

10, 100, 1000 and 10, 000 J2 of M. incognita /kg soil on bittergourd and round melon

under pot conditions and reported that significant reduction in plant growth was

observed at all the initial inoculum levels. The damaging threshold level in

bittergourd was found to be 1 J2/g soil as against 10 J2/g soil in round melon.

Munawar et al. (1991) showed that lentil plants were adversely affected by the

M. incognita. The reduction in plant length, fresh and dry weight and nodulation was

found significant at the inoculum level of 1000 or more root-knot nematode in both

lentil cultivars viz., L-209 and Lens-830. In lentil cv. Lens-830 at the lowest

inoculums level (10 J2) there was stimulation in plant length and fresh weight while

dry weight and nodulation showed reductions at this inoculums level. However, with

further increase in the inoculum level there was decrease in all plant growth

characters.

Khan and Husain (1991) observed that with increase in inoculum levels of M.

incognita there was a corresponding increase in the plant growth reduction of papaya

(Carica papaya L.). However, it was not statistically significant at lower inoculum

levels. Inoculation of 2000 juveniles per plant on the other hand caused significant

reduction in growth. Reproduction factor of root-knot nematode was significantly

reduced with an increase in the inoculum level of M. incognita.

Chan and Lopez (1992) studied the effect of different initial population

densities of M. incognita on the growth of tomato cv. Tropic under green house

conditions. They reported that 200 eggs/100 g soil was the tolerance limit of tomato.

Highest reproduction rate was observed at 600 eggs/100 g soil. Root-knot index

varied among the Pi and there was no correlation between reproduction rate and root-

knot index.

Pandey (1992) reported that with increasing inoculum densities of M.

incognita there was a corresponding decrease in root-shoot length, fresh and dry

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weight of plants and total chlorophyll content in leaves. The total phenolic content in

the leaves initially increased with the inoculum level but at the 10,000 and 20,000

inoculum level it returned to control levels. The root-knot index revealed a steady

increasing trend with every increase in inoculum level. The highest rate of nematode

reproduction was found at the lowest inoculum level and lowest rate of nematode

reproduction at the highest inoculum level. He further observed that nematode

inoculated plants showed stunting, chlorosis, delay in flowering and drying of few

basal leaves. The root system of all inoculated plants showed severe to very severe

root galling and reduction in the number of lateral roots.

Meena and Mishra (1993) observed a significant reduction in almost all the

plant growth parameters with increase in the level of nematode inoculum. Maximum

reduction in all the plant growth parameters was recorded at the inoculum level of

10,000 J2/pot which was followed by the level of 1000 J2/pot. At these levels plant

showed stunting, yellowing, wilting and sickly appearance. Significantly adverse

effects on the number of bacterial nodules was also observed with increase in the level

of nematode inoculum. The number of galls on roots, number of J2, J3 and adults of M.

incognita inside root tissue were observed to be increasing with increase in the levels

of inoculum.

Krishna and Krishnappa (1994) found that an inoculum level of 2 larvae/ g

soil was damaging threshold level on chickpea cv. Annegiri under green house

conditions. Increase in the level of larval inoculation resulted in proportional decrease

in plant growth and an increase in root-knot disease on chickpea. Hazarika and

Phukhan (1994) determined the effect of different initial inoculum levels (0, 10, 100,

1000, 5000 or 10,000 J2/pot) of M. incognita on brinjal var. JC-1. They found

significant reduction in height, root and shoot weight of plants at an inoculum level of

1000 nematodes/plant. Gupta et al. (1995) studied the effect of various initial

inoculum levels viz., 0, 10, 100, 1000, 2000, 5000 and 10, 000 J2 of Meloidogyne spp.

/kg soil on some cucurbitaceous crops. They found significant reduction in growth of

all the crops at initial inoculum levels of 1000 J2/pot. Galling was found maximum at

highest initial population density.

Khanna (1996) observed the adverse plant growth such as shoot height and

number of leaves in gladiolus cv. Vinks Glory inoculated with 10, 100, 1000 and

10,000 juveniles of M. incognita. The plants receiving 100 or more nematodes / pot

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started to show suppression of growth, 45 days after inoculation. Inoculum levels of

1000 nematodes showed reduction of growth and corm production in gladiolus while,

at 10,000, there was no emergence of plants.

Khanna and Chandel (1997) evaluated the different population levels of M.

incognita for their effect on the growth pattern of gladiolus cv Sylvia. Plants receiving

100 or more nematodes per pot showed suppression of growth 45 days after

inoculation. Highly infested plants with inoculum levels of 1000 and 10000 looked

short, weak and pale with shrivelled leaves and delayed emergence of spike. These

levels of nematode infestation also caused significant reduction in number of leaves,

leaves per spike and root weight. There was no emergence of plants at the highest

inoculum level of 10000. Nematode population revealed that the reproduction factor

decreased with increase in inoculum level. However, an increase in root-knot index

corresponded to increase in nematode inoculum levels.

Poornima and Vadivelu (1998) reported that M. incognita Race-3 was

pathogenic at 5000 and 10,000 J2/plant on turmeric (Curcuma longa L. cvs. BSR-1

and PTS-10). The leaves of the inoculated plants were pale in colour and shoot weight

reduced in both the varieties. Rhizome yield reduction in cv. BSR-1 was 25.0 and

18.6 % at 5000 and 10,000 nematodes / plant, respectively, while, it was 48.2 and

41.3 % in corresponding inoculum levels for PTS-10. In both the turmeric cultivars,

the levels of protein, carbohydrate, chlorophyll a, b, and total rhizome levels were

lower in plants inoculated with 10,000 juveniles when compared to healthy ones.

Kumar (2000) studied the pathogenic effect of root-knot nematode M.

incognita on tuberose, Polyanthus tuberose. Plant growth was significantly reduced

when the nematodes were inoculated at 10 J2/g soil. Similar trend was recorded even

with one J2/g soil. Nematode multiplication rate was significantly low at 10.0 J2/g soil,

whereas, at 0.01 and 0.10 J2/g soil there was an increase in the nematode

multiplication rate. The gall index was also more at 10.0 J2/g soil followed by 1.0 J2 /g

soil. Johnson et al. (2003) carried out an experiment to assess the damage potential

and pathogenic level of M. incognita on gladiolus and carnation under glasshouse

conditions. Growth parameters (shoot and root length, shoot and root weight and

number of leaves) were significantly reduced by different inoculum levels (10, 100

and 10000 J2/plant) of M. incognita in both gladiolus and carnation. The reproduction

rate of M. incognita on these crops was drastically reduced at higher inoculum level

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(10000 J2/plant). It was also observed that even 100 J2/plant were able to cause

economic damage to gladiolus and carnation.

Perveen et al. (2001) reported that with an increase in initial population

densities of M. incognita /pot there was a considerable increased reduction in the

shoot- root length, shoot- root dry weight and shoot- root fresh weight of Mentha

arvensis cv. Gomti. Total sugar, phenol, chlorophyll a, b and total chlorophyll content

in leaves were also decreased with increase in initial inoculum level of M. incognita.

Mostly, there was no significant difference in different parameters between two

corresponding initial population densities. Final nematode population in roots and

suckers in soil and root-knot index was observed to be directly proportional to initial

population of nematodes, while, reproduction factor was inversely proportional to

initial population densities. Singh and Hassan (2002) observed that the growth

parameters of bottelgourd were adversely affected at initial inoculum level of 100

J2/kg soil and beyond. The development of root galls, egg masses and nematode

population increased with the increase in initial inoculum level.

Khanna and Jyoti (2004) accessed the pathogenic potential of M. incognita on

Dianthus caryophillus. Nematodes were inoculated on three day old D. caryophillus

plant roots at population levels of 10, 100, 1000 and 10,000 second stage juveniles.

Plant growth was significantly reduced at the level of 1000 and 10,000 juveniles as

compared to control. Plant growth, root length, root weight, time taken to first bloom

and floral diameters were all adversely affected and stalk sturdiness was reduced, thus

reducing the commercial value of the flowers.

Khan et al. (2005a) conducted an experiment on the damage caused by M.

incognita (2000 J2/plant) to five common cultivars of chrysanthemum viz., Kiran,

Jaya, Orange Yellow, Sarad Bahar and Apsara. All the cultivars were found

susceptible to root-knot nematode infection. However, greater number of galls

developed on the cultivars, Orange yellow, Kiran and Sarad Bahar and the least galls

on Apsara. Soil population of the nematode increased in all the cultivars except

Apsara. As a result, plant growth was suppressed significantly in the cultivars orange

yellow, Kiran and Jaya. Khan et al. (2005b) assessed the effect of M. incognita

infection on three winter ornamental plants viz., hollyhock (Althea rosea), petunia

(Petunia hybrida) and poppy (Papaver rhoeas). These ornamental plants showed high

susceptibility to M. incognita and infestation of soil with 2000 eggs/kg soil resulted in

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stunted plant growth with pale green foliage of petunia. The reduction in flower

production was recorded as 37, 24 and 23% in petunia poppy and hollyhock

respectively.

Kumar and Haseeb (2006) reported that the reduction in all growth parameters

of chilli cv. Jwala increased with the corresponding increase in initial inoculum levels

of M. incognita. The significant reduction in all growth parameters was observed at

the lowest Pi (500 J2/4 kg soil) as compared to un-inoculated control. Maximum

reduction in number of fruits, fruit weight, shoot height, root length, shoot-root fresh

and dry weight was recorded at highest inoculum level (10,000 J2/4 kg soil) as

compared to un-inoculated control. The final population of nematode in roots and soil

and root-knot index were increased with corresponding increase in inoculum level,

while, the reproduction factor was decreased. Maximum root-knot index was

observed at the highest inoculum level, whereas, maximum reproduction factor was

observed at minimum inoculum level.

Joymati (2009) revealed that an increase in nematode inoculum was associated

with progressive reduction in various plant growth parameters of Allium porrum and

Centella asiatica. The growth parameter like shoot and root dry weight, number of

leaves and number of root-knot galls on the roots showed variation at different

inoculum levels. Plants with inoculum levels of 1000 and 10000 juveniles showed not

only reduction in plant growth but also stunting, yellowing of leaves and wilting

appearance. The number of galls on roots and number of different stages i.e J2, J3 and

adults of M. incognita inside the root were observed to increase with an increase in

the inoculum level. The rate of multiplication was found to be inversely proportional

to the population density.

Ganaie et al. (2011) observed a significant reduction in various plant growth

parameters of okra at and above the inoculum level of 1000 J2 / 2 kg soil of M.

incognita. Similarly, Azam et al. (2011) also observed the significant reduction in

plant growth parameters of tomato at and above the 1000 J2 per pot.

Khan and Fatima (2013) screened some important leafy vegetables viz.,

spinach, fenugreek and dill soa against M. incognita (2000 J2/kg soil) to determine

damage potential of the nematode on the growth parameters of these vegetables. They

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observed that all the vegetables were susceptible to M. incognita and order of

susceptibility was spinach followed by dill soa and fenugreek.

2.3: PATHOGENICITY OF ROOT-ROT FUNGUS, RHIZOCTONIA SOLANI:

Plants are means for the human survival and comforts starting from food,

home to several other requirements. A wide range of microorganisms including fungi,

bacteria and viruses are exploiting plants as a source of food and shelter, as in case of

all living forms on the earth. Some of these can act as pathogens, which cause a

variety of diseases that result in significant yield reduction leading to heavy economic

loss in many of the agricultural and horticultural species. Among these, fungal

diseases are rated as the most prevalent biotic stress contributing to yield loss.

According to a survey, contribution of fungal diseases towards total yield loss of

important crops in India is 18 - 3 1 % (Grover and Gowthaman, 2003).

Since De Condole (1815) first described the genus Rhizoctonia more than 100

species have been described so for. These species are distinguished from one another

primarily in respect to morphology and dimensions of sclerotia and monilioid cells

and on the basis of pathogenicity. Rhizoctonia solani is one of the most destructive

species of Rhizoctonia, occurring globally and causing various diseases on more than

500 hosts (Ogoshi, 1985). Rhizoctonia solani is a major cause of leaf blights, leaf

spots, damping-off, rots on roots, shoots and fruits, canker lesions on sprouts and

stolons and patches of turfgrasses (Fuhrer et al., 2004; Daughtrey and Benson, 2005;

Wu et al., 2006). Remarkable reports have also been well documented regarding the

pathogenic effect of R. solani on different plants (Haseeb, 1983; Gallo Llobet et al.,

1988; Otrysko and Banville, 1992; Gilligan et al., 1996; Karaca et al., 2000; Botha et

al., 2003).

Tello et al. (1990) established the pathogenicity of 10 isolates of R. solani on

cucumber cv. Corona and melon under green house conditions. They reported that all

the isolates of R. solani were pathogenic when inoculated at 16-18 leaves stage of

cucumber and melon plant. Otrysko and Banville (1992) studied the effect of R.

solani on the yield and quality of 10 cultivars of potato tubers. They observed a

significant reduction in total yield and quality of tuber in plants inoculated with the

fungus.

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Keinath (1995) studied the effect of different initial inoculum levels of R.

solani on the growth of 15 days old seedling of cabbage cv. Gaurmet and reported an

inversely proportional relationship between initial inoculum level and the crop yield.

Khangura et al. (1999) tested the pathogenic potential of 112 isolates of Rhizoctonia

sp. isolated from canola growing areas of western Australia on canola, crucifer,

leguminous and cereal crops. They found that most of the isolates were pathogenic to

canola at varying degree. Isolate ZG-5 was most pathogenic to crucifers, mildly

virulent to leguminous crops but nonpathogenic to cereal crops. However, isolate ZG-

1 was found pathogenic to legumes and cereals and highly pathogenic to canola.

Tiyagi et al. (1999) observed the reduction in various plant growth parameters

such as length, weight, root nodulation and chlorophyll content in lentil infected with

R. solani. There was a positive correlation between reduction in growth parameters

and increase in root-rot development in all the parameters. Sattar et al. (1999)

observed the collar and root-rot of opium poppy caused by R. solani. Their

pathogenicity revealed that R. solani produced chlorosis on the lower leaves with

small dark brown necrotic lesions on the collar region 3 days after inoculation. They

found that infection later increased around collar region and moved towards the stem

and root and typical symptoms of the disease appeared after 5-7 days of inoculation.

Severely infected plants toppled down leading to premature drying and death. Control

plants were found to be free from infection..

Botha et al. (2003) isolated Rhizoctonia species associated with black root-rot

disease of strawberries and assessed their pathogenic potential and relative virulence.

Both binucleate and multinucleate types were recovered from diseased roots and

identified as R. fragariae and R. solani, respectively. All Rhizoctonia isolates tested

were pathogenic to strawberry cv. Tiobelle, but R. solani (AG-6) was the most

virulent causing severe stunting of plants. Rhizoctonia fragariae (AG-A) and (AG-G)

were not as virulent as R. solani but also caused stunting of the plants, however, it

incited small, pale spreading lesions on infected roots.

Wright et al. (2004) reported petunia root-rot caused by R. solani and

observed that affected plants were randomly distributed in the greenhouses, and mean

disease incidence in all the greenhouses was 26%. The basal leaves turned yellow and

gradually became necrotic, and infected plants were often killed. They conducted

pathogenicity tests on potted, healthy, adult plants of petunia and noticed the wilt

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symptoms due to basal stem rot appeared 7 days after inoculation and all the

inoculated plants died within 27 days. Control plants remained disease free.

Soleimani and Kashi (2005) conducted the pathogenicity test to determine the

virulence of R. solani and isolates of binucleate Rhizoctonia sp. on gladiolus

(Gladiolus hybrid L.) cv. Silk. Their results revealed that R. solani and isolates of

binucleate Rhizoctonia were causal pathogens of root and stem rot of gladiolus. They

observed that all the isolates of binucleate Rhizoctonia caused severe rot on corms of

gladiolus and showed the severe damage. Differences in disease severity rating among

isolates were not significant. At 34 to 37 days after inoculation disease symptoms

began to appear first on upper parts of leaves and then on the lower part of stem. They

also found that corms were also infected as disease development progressed.

Prasad et al. (2008) tested the pathogenicity of R. solani and Fusarium

oxysporum on rose-scented geranium (Pelargonium graveolens). They used the

inoculum of ragi seed (infested with both the pathogens) @ 10g/ pot. Both the

pathogens exhibited typical root-rot and wilt complex symptoms on the diseased

plants. Symptoms were manifested as yellowing, stunting, defoliation and drooping of

leaves and branches, roots of affected plants showed severe rotting and lesions

developed over the stem at or below the soil line. Finally the whole plant wilted in a

few days.

Al-Abdalall (2010) investigated the effect of R. solani, F. culmorum and F.

oxysporum, which caused root-rot, on the growth and yield of wheat and barley

plants. They observed that there was a significant decrease in the growth and yield

parameters viz., the length, fresh and dry weight of roots and shoots, number of leaves

and the number of grains for each spike of infected plants compared with healthy

plants. Generally, fungi damaged wheat plants more than barley plants. R. solani had

the greatest effect on the growth and yield of wheat and barley as compared to F.

culmorum and F. oxysporum.

Haggag and El-Gamal (2012) conducted an experiment to assess the

pathogenic effect of R. solani isolates, separately, against some commercial tomato

cultivars, i.e. Ace, Brmodro, Castle-Rock and Super- Marmande, under glass-house

conditions. Results of pathogenicity study revealed that all tested R. solani isolates

had the pathogenic effect against the tested commercial tomato cultivars. The

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incidence of damping off disease caused by R. solani was in the range of 11.1 to 35.0

%, while the incidence of root rot disease was in the range of 3.3 to 38.5%.

Santosh et al. (2013) evaluated the pathogenic potential of R. solani on urd

bean. They reported that maximum severity was observed in plants sprayed with

mycelial suspension followed by inoculation with sclerotia. The plant at all growth

stages was found to be susceptible. However, disease severities varied with age.

Young plants were more prone to infection as compared to older ones

2.4: RACES OF ROOT-KNOT NEMATODES (MELOIDOGYNE SPP.):

The knowledge about the occurrence of biological races in plant parasitic

nematodes is essential and basic to studies of host-parasite relationships and to the

success of plant breeding programmes for disease resistance. Increasing evidences

indicate that every local population has a considerable amount of genetic variability

according to host specificity. The results obtained with one population of a species

should, therefore, be cautiously attributed to the other population of the same species.

This situation has created problems for the taxonomists, plant breeders and other

investigators because certain morphologically undistinguishable populations of a

nematode species often produce different reactions on the same host. Thus,

occurrence of intraspecific variations hamper our efforts to control plant parasitic

nematodes through breeding resistant varieties and crop rotation.

Ritzema Bos (1888) was probably the first to report that populations of

Ditylenchus dipsaci collected from different plants showed host preferences and

variations in pathogenicity. The stem nematode (Ditylenchus dipsaci) exhibits the

widest number of host races and there is controversy over the number 11 being

recognised by Seinhorst (1957), 21 by Hesling (1966) and 15 cited by Gubina (1988).

Such populations have been designated differently such as races, strains, biological

races, biotypes or pathogens etc. and the phenomenon as physiological specialization.

The knowledge about biological races in nematodes has greatly increased in the last

few decades and physiological variation has been observed in a considerable number

of phytoparasitic nematodes viz., Ditylenchus dipsaci, D. destructor, Aphelenchoides

ritzemabosi, A, fragariae, Radopholus similis, Rotylenchulus reniformos, Tylenchulus

semipenetrans, Belonolaimus longicaudatus and species of the genera Meloidogyne,

Heterodera, Globodera and Pratylenchus (Sidhu and Webster, 1981; Dropkin, 1988).

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Pathogenic variations among populations of Meloidogyne spp. is also not

uncommon. Christie and Albin (1944) and Christie and Havis (1948) experimentally

demonstrated the existence of races of Heterodera marioni (earlier name of root-knot

nematodes) and provided a basis on which Chitwood (1949) reclassified the group

into the genus Meloidogyne. Early evidences of the variation within different M.

incognita acrita populations was provided by Allen (1952). He found that several

populations of this species collected from cotton in California displayed a wide

diversity in host plant specificity. Similar were the results of Martin (1954) who found

that the cultures of M. incognita and M. incognita acrita from different cultivars of

cotton showed ranges from no parasitism to severe pathogenicity. Lider (1954)

reported considerable variability in the reaction of two species of Vitis to different

collections of M. incognita acrita and indicated existence of racial differences in the

ability to attack Vitis species.

Sasser (1954) showed that there were one or more crop plants which were not

attacked by some root-knot nematode species and that the non-hosts varied with the

nematode species. This observation made available a set of differential hosts for use

in separating the species and their races based on host reaction. Sasser and Nusbaum

(1955) observed that a population of M. incognita acrita that attacked cotton severely

was unable to attack tobacco whereas, another population from the neighbouring plots

attacked both.

Colbran (1958) recognized distinct physiological races in M. arenaria, M.

hapla, M. incognita and M. javanica. Riggs and Winstead (1959) reported that new

strains of M. incognita developed in the greenhouses which were capable of attacking

resistant tomato plants. Sasser (1963) worked on world-wide collections of

Meloidogyne spp. on nine host differentials and found physiological races in M.

incognita and M. arenaria. Graham (1969) discovered a new race of M. incognita in

field plots of flue-cured tobacco which attacked N.C. 95 tobacco, a cultivar resistant

to M. incognita. Golden and Birchfield (1978) examined a population of root-knot

nematode that was similar to M. incognita in morphology, but which could reproduce

on the moderately root-knot resistant soyabean cultivar Bragg. This population was

subsequently named as subspecies of M. incognita.

Southards and Priest (1973) collected 17 isolates of M. incognita from

different localities of Tennessee (U.S.A.) and studied their reaction on tomato

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(Rutgers), tobacco (NC-95), cotton (Mc Nair 1032), Watermelon (Dixie Queen),

Pepper (California Wonder) and Cowpea (Line M57-13N). They differentiated six

physiological races on the basis of host reaction of each race. Taylor and Sasser

(1978) gave a modified series of differential hosts for the identification of four

common species of Meloidogyne and their host races on the basis of their reaction on

six differential host test plants viz., tomato (Rutgers), pepper (California Wonder),

tobacco (NC-95), Cotton (Deltapine-16), peanut (Florrunner) and watermelon

(Charleston Gray). Out of 250 populations of root-knot nematodes they studied, 150

(60%) were identified as M. incognita, 60 (24%) as M. javanica, 22 (8.8%) as M.

hapla and 14 (5.6%) as M. arenaria. Analysis of their data revealed the existence of 4

races of M. incognita, 2 of M. arenaria and one each of M. javanica and M. hapla.

When the M. incognita populations were subjected to the host differential tests, 60%

failed to reproduce on tobacco and cotton. These populations were designated race-1.

Of the remaining population, 22% reproduced on tobacco but not cotton, 9%

reproduced on cotton but not tobacco and 5% reproduced on both cotton and tobacco.

These populations were designated as race 2, 3 and 4, respectively.

Maqbool and Hashmi (1984) conducted a wide survey of root-knot nematodes

in some host plants including fruit trees, vegetable crops and ornamental plants in

Sind, Pakistan and noticed that race 1 and 2 of M. incognita are not only more

common than M. javanica but also more widespread. The M. incognita had more host

plants than M. javanica, but certain plants were hosts for both species. Hartman and

Sasser (1985) reported the occurrence of race 1, 2, 3 and 4 of M. incognita from

agricultural areas.

Sogut and Elekcioglu (2000) conducted experiments for the Race

identification of Meloidogyne spp. infecting vegetables. They collected 38 root-knot

nematode populations and observed only race-1 of M. javanica and race 2 and 4 of M.

incognita. They further observed 6 populations which include 4 populations of M.

javanica, 1 of M. incognita and 1 of M. hapla that did not show appropriate reaction

according to the host test and therefore, could not determine their races. Mennan and

Ecevit (2001) examined three populations of root-knot nematode, Meloidogyne

incognita in vegetable growing areas of Egypt and observed that nematode

populations belonged to M. incognita Race-2.

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Carneiro et al. (2003) reported a new race of Meloidogyne javanica (Race-4)

for the first time in Brazil causing damage to Arachis pintoi. This population after

purification with only one egg mass and multiplication on tomato ‘Santa Cruz’ was

inoculated on differential host plants. The tomato cv. Rutgers, tobacco cv. NC-95,

watermelon cv. Charleston Gray, pepper cv. California Wonder and peanut cv.

Florunner were good hosts and cotton cv. Deltapaine 16 was immune against M.

javanica Race-4. Karajeh et al. (2006) reported the occurrence of race 1 and 2 of M.

incognita and race-2 of M. arenaria from various vegetable and fruit trees in Jordan.

Robertson et al. (2009) collected 140 populations of the genus Meloidogyne

from horticultural regions of Spain. Using a modified North Carolina differential host

test for the identification of races of Meloidogyne spp., 13 Meloidogyne populations

did not fit into the published race scheme. These populations had very limited host

ranges, reproducing only on susceptible tomato cv. Marmande and sometimes also on

tobacco cv. NC-95 and the pepper cv. Sonar in the case of Meloidogyne arenaria.

They did not reproduce on cotton or peanut. The species and new races were

identified as M. incognita Race-5 (6 populations) and race-6 (2 populations) and M.

javanica race 5 (2 populations), with new records of M. arenaria Race-3 (2

populations) and M. javanica Race-1 (23 populations).

Devran and Sogut (2011) tested 95 samples of M. incognita, 60 samples of M.

javanica and 7 samples of M. arenaria for the race identification of the respective

nematode species by using North Carolina Differential Host Test. They identified the

Race 2 and 6 of M. incognita from 58 and 2 samples, respectively. Race-1 of M.

javanica was identified from all 28 samples. Race-2 and 3 of M. arenaria was

identified in 5 and 2 samples, respectively.

The chances of occurrence of variability within the different Indian

populations of Meloidogyne species are more because of the great diversity in agro-

climatic conditions, different cropping patterns and agricultural practices prevalent in

the country but there is still little information about the occurrence and distribution of

physiological races of Meloidogyne species in India. Bhardwaj et al. (1972) reported

the occurrence of M. incognita Race-2 and race-4 from Solan area of Himachal

Pradesh. Raj and Gill (1982) studied five populations of M. incognita collected from

Delhi, Jabalpur, Kanpur, Kayangulum and Udaipur. They found these populations

identical to race-1 and race-2. Routray and Das (1982) studied 11 populations of M.

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incognita collected from Bhubanaswar and Cuttack and identified them to belong to

race-1 and 2. They observed race-1 infection on Basella alba, Cucurbita pepo and

Momordica charantia plants. Meloidogyne incognita Race-2 was found attacking

Solanum melongena, Vigna radiata, Lycopersicon esculentum, Musa paradisiaca,

Abelmoschus esculentus, Vigna sinensis, Cucumis sativa and Luffa acutangula plants.

Krishnappa and Setty (1983) studied 127 populations of root-knot nematode

M. incognita, collected from different region of Orissa and Karnataka. They reported

that 86 (67.7%) belonged to race-2 and only 10 (7.9%) to race-3. They further noted

that all 33 populations from Northern, North-Eastern and Eastern Coastal zones were

comprised of race-1. Out of 10 populations from the deep Southern zone, 9 belonged

to race-1 and only 1 to race-3. Amongst the 84 populations from Karnataka zone, 44

(52.4%) belonged to race-1, 34 (36.9%) to race-2 and 9 (10.7%) to race-3. The race-1

was found to occur in all the zones, race-2 was confined to Karnataka while race-3

was present in Karnataka and deep Southern zone. Haider et al. (1988) identified

races 1 and 2 of M. incognita from the Bihar. Bajaj et al. (1986) identified all the four

races of M. incognita from Haryana. Khan et al. (1994) observed the occurrence of

three races (1, 2 and 3) of M. incognita on Carica papaya L. in three districts of

Madhya Pradesh, India. The overall frequency of occurrence of race 1, 2 and 3 was

42.2, 35.6 and 22.2 per cent, respectively in the three districts.

Khan and Khan (1991) collected 1256 populations of Meloidogyne incognita

and 442 populations of M. arenaria in eight district of Western Uttar Pradesh, India

viz., Aligarh, Bulandshahr, Gaziabad, Meerut, Muzaffarnagar, Saharanpur, Dehradun

and Nainital. All the four races of M. incognita were found in all districts, except in

Dehradun and Nainital, where no race 3 populations were recovered. Meloidogyne

incognita Race-1 was the most frequently identified race in their survey and 35% of

the M. incognita populations were race 1. Race-2, 3 and 4 made up 27, 18 and 21% of

M. incognita populations, respectively. The M. arenaria was found in all eight

districts, and all populations of this species were race-2. Race-1 was found in greatest

frequencies in the districts of Aligarh, Gaziabad and Saharanpur, whereas, race 2 was

most frequently found in Muzaffarnagar. In Bulandshahr and Meerut, race 1 and 3

occurred in approximately equal frequencies, whereas in Dehradun, races-2 and 4

were equal in occurrence. Race-4 was the predominant host race found in Meerut and

Nainital.

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Sharma and Gill (1992 and 1998) collected 17 populations of M. incognita

from 11 states and two Union Territories of India for their reaction on differential host

plants. Out of the 17 populations, 12 were classified under race-1, 3 under race-2 and

only one under race-4. Their findings suggest that race-1 was very widely spread,

whereas race-4 was more aggressive on test plants. Race-1 was observed from

Udaipur, Pusa, Kayangulam, Hissar, Jabalpur, Delhi, Chandigarh, Bhubaneswar,

Kanpur, Pant Nagar, Solan and Bangalore. Race-2 was found at Rahuri, Bajora and

Coimbatore, race-3 at Jodhpur and race-4 at Shimla.

Ramakrishnan et al. (1993) conducted experiments on four different locations

in Pondicherry for the race identification of M. incognita infecting okra. They

observed that population of M. incognita prevalent in Pondicherry was race-3.

Srivastava (2001) identified the race-2 of M. incognita infecting vegetables (Tomato

and Brinjal) from Pondicherry.

Khan et al. (2003) examined 295 M. javanica isolates collected from nine

districts of Uttar Pradesh. These isolates showed pathogenic variability when

inoculated on the pepper cultivars California Wonder and Suryamukhi Green. The M.

javanica that infected Suryamukhi Green but not to California Wonder were

designated as pepper race-1 and the populations that infected both the cultivars were

designated pepper race-2. Race-1 was more frequent than race-2 in Almora, Pauri

Garhwal, Basti, Gorakhpur, and Deoria, whereas, race-2 was more frequent than race

1 in the Dehradun, Farrukhabad, Hardoi and Sitapur districts. The overall frequencies

were 70% and 30% for race-1 and race-2, respectively, in the study area. Naidu et al.

(2007) collected the plant and soil samples from root-knot nematode infested areas of

Chittoor district from Andhra Pradesh and identified the race-2 of M. incognita by

applying host differential test.

2.5: INTERACTION OF ROOT-KNOT NEMATODE AND ROOT-ROT

FUNGUS:

In the soil ecosystem, roots of plants are constantly exposed to the multiplicity

of organisms including fungi, nematodes and viruses etc., many of which are common

components of the soil biosphere. As they occupy the same environmental niche, such

organisms besides influencing the plants, are likely to influence each other as well.

Plant parasitic nematodes are quite capable of causing severe plant diseases and

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reduction in crop production. Since they are often involved with other disease causing

organisms such associations lead to more than additive damage referred as “complex

diseases”, the name having been derived from the presence of two or more disease-

causing organisms (Jenkins and Taylor, 1967). Concomitant occurrence is common in

nature and the limitation of research to single pathogens is unrealistic since the soil

contains an extensive flora and fauna of microorganisms which may cause plant

diseases (Back et al., 2002). Ever since Atkinson (1892) first observed that the

severity of Fusarium wilt of cotton was enhanced in the presence of root-knot

nematode, vast numbers of studies have focused on the study of potential

interrelationships between nematodes and associated organisms. Khan and Dasgupta

(1993) suggested that a disease complex should be considered multi-causal only if its

causal factors are both biologically and statistically established.

Soil-borne disease complexes involving species of Rhizoctonia and root-knot

nematodes have led to synergistic increases in damage of crop production. The

interaction of R. solani with different species of Meloidogyne like M. javanica

(Kanwar et al., 1988; Mehta et al., 1989; Abdel-Momen and Starr, 1998; Agu, 2002),

M. hapla (Khan and Muller, 1982; Fagbenle and Inskeep, 1987; Scholte and Jacob,

1989) and M. arenaria (Garcia and Mitchell, 1975) etc, have been reported on

different plants. Although, numerous reports have been published on interactions

between soil-borne fungal pathogens and plant parasitic nematodes (Powell, 1971;

Bergeson, 1972; Pitcher, 1978; Taylor, 1990; Back et al., 2002), nothing is known

about such complex interactions on P. atropurpureum.

Batten and Powell (1971) studied Rhizoctonia-Meloidogyne disease complex

in Flue-cured tobacco. An important aspect of their experiment was that R. solani

alone does not inflict significant damage to tobacco plants as this fungus was

evidently unable to colonize healthy tobacco roots. If, however, root-knot susceptible

plants were previously exposed to M. incognita for at least 10 days, R. solani was

capable of penetrating the roots and promoting necrosis. They observed that if M.

incognita preceded R. solani by 10 days or 21 days in roots of greenhouse grown

tobacco plants, root-rot was more extensive then when the nematode and fungus were

introduced either simultaneously or separately or when R. solani was added after

artificial wounding. Histological examination of galled roots 72 days after inoculation

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with R. solani revealed extensive fungal colonization in the root-knot susceptible

cultivar ‘Dixie Bright 101’ when M. incognita preceded R. solani by 21 days.

Hazarika and Roy (1974) studied the interrelationship between R. solani and

M. incognita on egg plants (Solanum melongena L.) and they showed that the number

of galls on roots as well as the number of egg masses were significantly greater in

plants inoculated with nematode and fungus together than in those inoculated with

nematode alone. Moreover, the growths of egg plant were not affected significantly

by the attack of M. incognita or R. solani alone or by their combination.

Chhabra et al. (1977) investigated the interaction involving R. solani and M.

incognita on 7 day old okra plants. They revealed that there was a significant

reduction in the shoot and root lengths and their wet and dry weight in the plant

receiving the inoculum of a fungus + nematode simultaneously, nematode + fungus

10 days after, and fungus + nematode 10 days after, over control while nematode

alone reduced the shoot length only. Maximum reduction in the plant growth was

noticed where fungus + nematode were inoculated simultaneously. Fungus alone has

almost no effect on plant growth reduction.

Reddy et al. (1979) reported that inoculations of Phaseolus vulgaris with M.

incognita alone or simultaneously with R. solani or 10 days prior to fungal infection

reduced plant height and fresh weight of shoot and gave the maximum root-knot

infection. Simultaneous inoculations of both the pathogens caused greater damage

than either organism acting alone.

Chahal and Chhabra (1984) studied that M. incognita and R. solani separately

as well as in combination significantly reduced the shoot length, shoot weight and

root –weight as compared to un-inoculated control. The synergistic effect of

simultaneous inoculation was apparent from the significant reduction of shoot weight

and length and root weight in comparison to either of the pathogens alone. Inoculation

of M. incognita 3 weeks prior to R. solani significantly reduced the shoot weight and

length in comparison to inoulation of R. solani 3 weeks prior to M. incognita. It

suggests a predisposition of the seedling roots by nematode for subsequent damage by

R. solani. The maximum number of galls and nematode population was observed with

the inoculation of M. incognita three weeks prior to R. solani and this may be because

of longer exposure of roots to nematode invasion than in the treatment where R.

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solani was inoculated 3 weeks prior to M. incognita and in this case the number of

galls as well as the nematode population was minimum.

Husain et al. (1985) reported that peas were damaged by M. incognita or R.

solani but plant growth was suppressed even further when plants were inoculated with

both organisms with the maximum effect occurring when the two were inoculated

simultaneously. Abu El-Amayem et al. (1985) observed that the soybean plants were

damaged by M. incognita and R. solani but plant growth was depressed even further

when plants were inoculated with both organisms, with the maximum effect occurring

when the two were inoculated simultaneously.

Siddiqui et al. (1987) reported that M. incognita, Rotylenchulus reniformis and

R. solani significantly reduced plant growth of okra when inoculated separately,

however the reduction was more pronounced in plants inoculated with the fungus

along with either of the nematodes. A similar reduction was noted in the water

absorption capability of roots. Nematode multiplication was however, retracted by the

presence of the fungus. Varshney et al. (1987) reported the inoculation of cowpea

with M. incognita and R. solani led to breakdown of resistance to both organisms and

the greatest decrease in plant dry weight occurred when the nematode was inoculated

two weeks before the fungus.

Khan and Husain (1988b) reported that individually, R. solani was the most

aggressive pathogen followed by M. incognita and R. reniformis. While,

concomitance of nematode and fungus was more damaging than the association of

both nematode species. The association of R. solani with M. incognita caused

distinctly greater plant growth reduction than its association with R. reniformis.

Irrespective of the pathogen inoculated, unbacterized plants suffered greater damage

than the bacterized ones. Inoculation of Rhizobium 15 days prior to any test pathogen,

both singly or in various combinations, resulted in significantly reduced plant growth,

poor nematode multiplication, low root-knot index and improved nodulation in

comparasion with its inoculation 15 days after the test pathogen (s). There was no

significant difference in plant growth reduction of bacterized plants whether

inoculated simultaneously with either nematode species and the fungus or when the

nematode inoculation preceded fungus but, on the other hand, there was significantly

less reduction in plant growth when fungus preceded nematode inoculation.

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Godoy et al. (1990) reported that in okra disease characterized by stunting,

defoliation, severe root galling, extensive root decay and premature death of plants. It

was found that M. incognita Race-1, R. solani and F. solani were frequently

associated with diseased roots. Under greenhouse conditions, M. incognita inoculated

alone or in combination with R. solani and/or F. solani was the main pathogen,

considerably reduced the leaf dry weight and fruit yield of the okra cv. Clemson

Spineless. Rhizoctonia solani and F. solani when inoculated individually significantly

reduced leaf dry weight. Meloidogyne incognita - R. solani together had an additive

effect on leaf dry weight and fruit yield, whereas, combinations R. solani - F.solani,

M. incognita - F. solani and M. incognita - R. solani - F. solani produced an

antagonistic effect on leaf dry weight. Khan and Husain (1990) studied the effect of

interaction of variable inoculum levels of R. reniformis, M. incognita and R. solani on

cowpea. In the nematode fungus interaction the greatest damage was observed when

nematode inoculum of either nematode species was lowest and that of the fungus was

highest. Irrespective of inoculum, R. solani was antagonistic to the multiplication of

each of the nematode species.

Ali and Venugopal (1992) studied the disease complex of M. incognita and R.

solani in cardamom (Elettaria cardamomum) in Karnataka, India. They observed

significant damage in various plant growth parameters on individual inoculation of M.

incognita and R. solani. However, the severity of damage enhanced when both the

pathogens were present either simultaneously or sequentially. Severe root rotting of

cardamom seedlings occurred when the M. incognita preceded R. solani by 21 days,

high mortality was recorded in this treatment followed by simultaneous inoculation of

fungus and nematode and then fungus preceding nematode. They also observed

significant differences for all the morphological parameters except rhizome girth,

however, highest reduction in leaf area, shoot length, shoot weight, root length and

weight and rhizome girth were recorded in the treatments where nematodes were

followed by fungus

Anwar et al. (1997) studied the interaction between M. incognita and R. solani

on soybean and observed significant alterations in chlorophyll a and b by

simultaneous, sequential and individual inoculations but more damage was observed

in simultaneous inoculation than other treatments.

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Kumar and Vadivelu (1997) reported that the inoculation of M. incognita, R.

reniformis and R. solani either individually or in combination significantly affected

the plant height, fresh and dry weights of shoots and roots. However, the maximum

reduction was observed in plants which received all the three pathogens together. The

nematode multiplication rate was affected when either of the nematodes were

combined with R. solani or when both the nematodes were present in the same plant.

Walker (1997) observed that a disease complex involving M. incognita and R.

solani was associated with stunting of grapevines in field survey. He observed that

root-rot caused by R. solani was higher when grapevines were inoculated with M.

incognita and R. solani either concomitantly or sequentially as compared to when R.

solani present alone. The root-rot was highest when nematode inoculations preceded

the fungus. Shoot weight was lowest when vines were inoculated with M. incognita

13 days before inoculation with R. solani as compared with inoculations when both

the nematode and fungus were inoculated simultaneously.

Anwar and Khan (2002) studied the interactive effect of M. incognita and R.

solani on soybean. They observed a significant decrease in shoot and root length and

fresh and dry weight in different treatments of inoculation. Simultaneous inoculation

of both pathogens resulted in maximum decrease in various plant growth parameters,

compared with R. solani one week prior and after M. incognita combinations. They

also found that inoculation of nematode and fungus separately or in combination also

had an adverse effect on the physiological parameters of soybean. It was noticed that

fungus alone did not cause significant reduction in oil content of soybean. Further, it

was observed that the enzyme nitrate reductase activity was affected with prior and

after inoculation of M. incognita and R. solani followed by simultaneous inoculation,

however, fungus alone did not exhibit any considerable reduction.

Kumar et al. (2004) observed an inverse relationship between initial inoculum

densities of M. incognita / R. solani and plant length, fresh and dry weights of black

henbane (Hyoscyamus niger). Significant reduction in plant dry weight was observed

at initial inoculum of 50 J2 of M. incognita and 1.0 g culture of R. solani / pot. The

initial inoculum densities and final nematode population / root-knot index showed a

direct relationship. Simultaneous or sequential inoculation of both the pathogens

reduced plant growth more than when inoculated separately.

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Dubey and Trivedi (2006) studied the interaction of M. incognita with R.

solani and Fusarium alone and in combination on okra (Abelmoschus esculentus).

Combined inoculation with M. incognita + R. solani + Fusarium was more damaging

than inoculation with M. incognita + R. solani or M. incognita + Fusarium. In

combined inoculation the magnitude of each individual organism was modified. The

close proximity of infection court of the nematode and fungi probably enhanced the

possibility of exchange of toxic metabolites from one feeding site to the other thus

interfering in the establishment of normal host parasite relationship. Multiplication

rate of nematode was poor in the presence of fungi because of tissue destruction

caused by fungi much before the completion of nematode life cycle. Thus, the

concomitant effect of nematode and fungi caused greatest reduction in growth of okra.

Mokbel et al. (2007) reported that the combined infection of M. incognita plus

any of the tested fungi namely R. solani, Macrophomina phaseolina and F. solani

resulted in significant reduction in the egg masses on sunflower cv. Myak. Plant

growth reduction and disease severity were greatly evident when M. incognita was

inoculated simultaneously with R. solani. Treatments with M. incognita in

combination with different inoculums levels of the tested fungi caused significant

reduction in number of root galls and nematode egg masses and the dry weight of

sunflower plants. Inoculation of plants with any of the tested fungi either at the same

time or one week before M. incognita resulted in significant reduction in dry weight

of plants, number of root galls and nematode egg masses.

Bhagawati et al. (2007) studied interaction of M. incognita and R. solani on

okra. Their findings revealed that root-knot nematode significantly increased the pre

and post emergence damping off and were significantly higher in the treatments with

simultaneous inoculation of M. incognita and R. solani as compared to the treatment

with fungus alone. Further the post emergence damping off was found to be

significantly higher where nematode inoculation preceded fungus inoculation. There

was a significant reduction in the growth parameters in all the treatments as compared

to un-inoculated control. Maximum per cent reduction of plant height shoot weight

and root weight was recorded in simultaneous inoculation of both the pathogens

followed by the treatments where nematode inoculation preceded fungus. The growth

reduction in N+F and N+F10 were significantly higher as compared to F+N10. The

number of galls and egg masses in roots and nematode population in soil were found

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maximum in nematode alone treatments. The minimum number of galls, egg masses

and nematode population were recorded in N+F treatment.

Kumar and Haseeb (2009) indicated that highest reduction in plant growth and

yield parameters was observed in simultaneous inoculation of M. incognita and R.

solani followed by nematode seven days prior to fungus, fungus seven days prior to

nematode, nematode alone and fungus alone in tomato cv. K-25. However, highest

reproduction rate and root-knot index were observed in plants inoculated with

nematode alone followed by nematode prior to fungus, nematode-fungus

simultaneously and fungus prior to nematode, respectively. The results also indicated

that root colonization by fungus was significantly high in the presence of M. incognita

as compared with the fungus alone.

Al-Hammouri et al. (2010) examined the interaction of R. solani and M.

incognita on chili to investigate whether R. solani and M. incognita have a synergistic

effect on chili. They inoculated M. incognita at the rate of 5,000 eggs per plant and R.

solani was inoculated at the rate of five agar pellets (1-cm in diameter) per plant.

They observed that neither reproduction rate of M. incognita in the presence of R.

solani in chili roots, nor R. solani infection in the presence of M. incognita was

affected in simultaneous inoculation of both the pathogens. The simultaneous

inoculation had no effect on plant dry biomass, while the sequential inoculation had a

minor effect. In the sequential experiments, higher frequencies of R. solani were

observed when R. solani preceded M. incognita than when M. incognita preceded R.

solani and the effect of the sequential inoculation on several measured parameters was

significant. Interaction of R. solani and M. incognita was more apparent when both

pathogens were inoculated sequentially to soil rather than when inoculated

simultaneously.

Yaqub et al. (2011) revealed that there was a maximum reduction in shoot and

root length, fresh weight and number of pods in bean plants (Phaseolus vulgaris L.)

receiving the inoculum of the R. solani and M. incognita simultaneously. The fungus

alone caused comparatively less effect than the nematode. Similar progressive

decrease in chlorophyll and carotenoid content was also observed in concomitant

inoculations. The root-knot index was highest where nematodes were inoculated

singly and was a significantly reduced in presence of fungus. Conversely, the

simultaneous inoculation of both the pathogens gave maximum root-rot index.

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Malhotra et al. (2011) indicated that the plant growth of Capsicum annuum L.

was adversely affected when inoculated with M. incognita and R. solani as compared

to un-inoculated control. Although, each pathogen was able to reduce the plant

growth, the combined infection of nematode and fungus resulted in synergistic effect.

Inoculation of M. incognita 15 days prior to R. solani significantly reduced all the

plant growth parameters as compared to inoculation of R. solani 15 days prior to M.

incognita. They found that root-knot index, number of galls and egg masses in roots

were minimum in plants inoculated with nematode and fungus simultaneously.

Vidya Sagar et al. (2012) observed that all plant growth parameters viz., shoot

and root length, shoot and root weight of tomato cv. Pusa ruby were significantly

decreased in all the treatments when compared to un-inoculated control. The

maximum reduction in various plant growth parameters was observed in which M.

incognita was inoculated 7 days prior to R. solani, followed by simultaneous

inoculation of both the pathogens and R. solani 7 days prior to M. incognita. Although

the individual inoculation of M. incognita and R. solani showed significant decrease

over control, the reduction was more severe when both were inoculated

simultaneously and sequentially. They further observed that root-knot disease and

root-knot nematode population was affected by the presence of R. solani. The root-

knot index, nematode population, number of egg masses per root system and number

of eggs per egg mass were minimum in plants inoculated with fungus prior to

nematode treatment as against maximum with the treatments in the nematode alone.

2.6: LIFE CYCLE OF ROOT-KNOT NEMATODE MELOIDOGYNE

INCOGNITA:

Muller (1883) was the first to describe the life cycle of Meloidogyne spp. Later

many contributions were made on the morphology of different developmental stages

and the duration of the life cycle of Meloidogyne spp. under different environmental

conditions and with several host plants in relation to their age and nutritional status

(Tyler, 1933; Chitwood, 1949; Bird, 1979; Mohan and Mishra, 1994; Mahapatra and

Swain, 1999; Luang and Bora, 2005).

Tyler (1933) found that the minimum time required for the life cycle of

Meloidogyne sp. was 87 and 25 days on tomato seedling at 16.5 and 27 0C

respectively. Tarjan (1952) reported that the egg production of females started 39

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days after inoculation for M. incognita, M. arenaria and M. javanica and 37 days for

M. incognita acrita at 21 0C on Antirrhinum majus. Dhawan and Sethi (1976)

observed that M. incognita required 36 days to complete it’s life cycle on little leaf

affected egg plants.

Sharma and Trivedi (1992) studied the life cycle of M. incognita on two

cultivars (UM-83 and UM-34) of Trigonella foenum-graecum. The second stage

juveniles (J2) penetrated the fenu-greek roots within 24 hours. The J2 became

sedentary within three days after inoculation in UM-83 whereas, in UM-34 the first

sedentary juvenile was seen six days after inoculation. The second moult of J2 was

observed nine days after inoculation in UM-83 and 13 in UM-34. This moult gave rise

to the third stage juvenile J3 which lasted for 8 days in both cultivars. The fourth stage

juvenile lasted for seven days in UM-83 and 12 days in UM-34. The fourth moult

followed rapidly and gave rise to a young female. The females increased in length and

width and assumed typical swollen shapes. Egg formation was seen in the female

body at 36 days after inoculation in UM-83 and 44 days after inoculation in UM-34.

The females secreted a gelatinous matrix and most of the eggs in the matrix contained

first stage juveniles by 38 days after inoculation in UM-83 and 46 in UM-34. Males

were rare in UM-83, whereas large numbers were observed in UM-34. Hence the life

cycle of M. incognita from egg to egg was completed in 42-44 days in UM-83 and in

48-50 days in UM-34 at 22 ± 30C day temperature.

Mohan and Mishra (1994) studied the life cycle of M. incognita on French

bean cv. ‘Pusa Parvati’. They observed that penetration of second stage juveniles (J2)

started within 12 hours and continued till 48 hours after inoculation. Maximum

penetration was recorded at 48 hours after inoculation. After penetration the juvenile

remained in its vermiform stage for approximately 6 days. The second and third moult

occurred by 8th

and 14th

day after inoculation and the juveniles were still observed to

be non-feeding. They gradually enlarged to acquire the fourth and final moult from

pre-adult stage to become adult male and female. Adult females oviposited after 24

days of inoculation. The total life cycle of M. incognita was completed after 31 days

of inoculation, when the first hatched J2 was recorded from egg mass.

Singh and Kumar (1998) studied the life cycle of M. incognita on Japanese

mint (Mentha arvensis). The second stage juveniles started invading the young mint

roots 48 hours after inoculation and continued upto 16 days. Second moult occurred

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on 5th

day after inoculation indicating the appearance of third stage with posterior

ends round with spike tail. Third stage lasted for 4 days when third moult occurred

resulting into 4th

stage male and female juveniles. A valvular plate in the fourth moult

was observed on 18th

day after inoculation resulting into mature female and male.

Deposition of gelatinous matrix without any egg was observed on 22nd

day after

inoculation. Second generation J2 appeared on 29th

day after inoculation. Thus, life

cycle of M. incognita on Japanese mint (Mentha arvensis cv. ‘Shivalik’ was

completed from J2 to J2 in 29 days at ambient temperature 130C- 37

0C during March

and April.

Mahapatra and Swain (1999) reported that life cycle (J2 to J2) of M. incognita

on black gram was completed within 32 days at a temperature range of 18-340C. The

juveniles started penetrating roots as early as 12 hrs after inoculation and continued

upto 6th

day. Initiation of moulting in J2 was observed on 8th

day of inoculation and

completed on 14th

day. Third moulting started on the 16th

day and was completed on

22nd

day of inoculation and young females developed. Mature females secreted egg

sacs on 26th

day of inoculation. They further observed that life cycle of M. incognita

was delayed by two days in the presence of Fusarium oxysporum.

Verma and Anwar (1999) observed that the penetration of second stage

juveniles of M. incognita in roots of pointed Gourd (Trichosanthes diocia Roxb.)

continued upto 9 days with maximum numbers of J2 penetrating on 6th

day. After

penetration, the juveniles oriented themselves longitudinally near the vascular area

behind the root tip and started moulting in 72 hours. Young females appeared 18th

day

after inoculation. Deposition of gelatinous matrix and egg masses started from 20- 24

days followed by emergence of J2 (2nd

generation). Majority of eggs were retained in

the egg mass. The larval penetration in roots resulted in the formation of necrosis and

irregular shaped giant cells. The infection also caused the formation of confluent

round to spindle shaped galls laterally on roots.

Sharma et al. (2000) reported that M. incognita completed its life cycle from

J2 to the formation of adult female with egg mass in 29 days on groundnut plants.

Khan (2002) reported that the penetration of M. incognita juveniles in papaya roots

was reduced in the presence of Fusarium solani. Only 66.3% penetrated juveniles

developed into females in M. incognita alone in comparison to 42.7%, where F.

solani was present along with M. incognita. Fecundity was also reduced with an

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average of 207 eggs per egg mass in roots infected with M. incognita and F. solani as

compared to 356 eggs with M. incognita alone. Moreover, the percentage of male was

high (7.3) in roots infected with M. incognita and F. solani. Presence of F. solani

delayed the life cycle of the root-knot nematode by 9 days. Khan (2003a) observed

that M. incognita Race-2 completed it’s life cycle in 27 days in balsam (Impatiens

balsamina L.).

Luang and Bora (2005) studied the life cycle and reproductive potential of M.

incognita on Corchorus capsularis and C. olitorius. They revealed that most of the J2

invaded the roots of C. capsularis and C. olitorius. The second molt occurred by 8th

and 7th

day of inoculation and third molt occurred only after 14th

day of inoculation on

both the species of jute. By this time the nematode become completely non feeding

and started enlarging gradually to attain the globose pre-adult to adult stage. The

fourth and final molt from the globus pre-adult to adult female and male occurred

only after 20th

and 22nd

day of inoculation in C. capsularis and C. olitorius,

respectively. Oviposition started almost after 25 days of inoculation in C. capsularis

jute and same was recorded after 27th

day of inoculation in C. olitorius jute. The

hatched juveniles were observed on infected roots of C. capsularis and C. olitorius

jute only after 29th

day of inoculation. Khan and Ashraf (2005) studied life cycle

Meloidogyne incognita and found that it required 32 days to complete their life cycle

on lettuce at a temperature ranging between 18- 250C.

Al-Sayed et al. (2011) studied the life cycle of M. incognita on tomato, okra,

pepper, cowpea, sunflower and soybean. They observed that life cycle of M. incognita

varied according to temperature and host type. In tomato, okra, pepper and cowpea M.

incognita required 28 days at 32±5 0C to develop and produce second stage juveniles

of the next generation, 21 days were sufficient in sunflower but 35 days were required

in soybean. At lower temperature of 20±5 0C the nematode needed 35 days to produce

the next generation in tomato, sunflower, okra and soybean, 42 days in cowpea and 49

days in pepper. In general lower temperature prolonged the nematode life cycle.

Hernandez-Ochandia et al. (2012) observed that life cycle of M. incognita in tomato

was compleated in 24 days.

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Management of root-knot nematode, M. incognita and root-rot fungus, R. solani:

Plant diseases need to be controlled to maintain the quality and abundance of

food, feed, and fiber produced by growers around the world. Different approaches

may be used to prevent, mitigate or control plant diseases. Beyond good agronomic

and horticultural practices, growers often rely heavily on chemical fertilizers and

pesticides. Such inputs to agriculture have contributed significantly to the spectacular

improvements in crop productivity and quality over the past 100 years. However, the

environmental pollution caused by excessive use and misuse of agrochemicals has led

to considerable changes in people’s attitudes towards the use of pesticides in

agriculture. Today, there are strict regulations on chemical pesticide use, and there is

political pressure to remove the most hazardous chemicals from the market.

Additionally, the spread of plant diseases in natural ecosystems may prevent

successful application of chemicals, because of the scale to which such applications

might have to be applied. Consequently, some pest management researchers have

focused their efforts on developing alternative inputs to synthetic chemicals for

controlling pests and diseases. Among these alternatives are those referred to as

biological controls. The biological control of some plant diseases has been found

effective and is gaining importance day by day as one of the cheapest control

measures.

The term “biological control” or “biocontrol” has been applied to the use of

the natural products extracted or fermented from various sources. These formulations

may be very simple mixtures of natural ingredients with specific activities or complex

mixtures with multiple effects on the host as well as the target pest or pathogen.

While such inputs may mimic the activities of living organisms, nonliving inputs

should more properly be referred to as biopesticides or biofertilizers, depending on

the primary benefit provided to the host plant. (Pal and McSpadden, 2006).

2.7 : Management approach by using fungal biocontrol agents:

The present review particularly deals with the studies related to the

management of disease complex involving species of Meloidogyne and Rhizoctonia

on different plants. Besides, a separate account of review of literature pertaining to the

management of species of Meloidogyne and Rhizoctonia has also been given when

they were present alone on different plants.

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Paecilomyces lilacinus has an almost worldwide distribution occurring most

frequently in warmer climates (Samson, 1974; Domsch et al. 1980; Dunn et al.,

1982). Lysek (1966) first reported the association of the fungus P. lilacinus with the

eggs of Meloidogyne spp. The P. lilacinus is highly adaptable in its life strategy,

depending on the availability of nutrients in the surrounding environments it may be

entomopathogenic (Fiedler and Sosnowsk, 2007), mycoparasitic (Gupta et al, 1993),

saprophytic (Tigano-Milani et al, 1995), as well as nematophagous.

Before infecting a nematode egg, P. lilacinus flattens against the egg surface

and becomes closely appressed to it. Paecilomyces lilacinus produces simple

appressoria anywhere on the nematode egg shell either after a few hyphae grow along

the egg surface, or after a network of hyphae form on the egg. The presence of

appressoria appears to indicate that the egg is, or is about to be infected. In either

case, the appressorium appears the same, as a simple swelling at the end of hyphae,

closely appressed to the eggshell. Adhesion between the appressorium and nematode

egg surface must be strong enough to withstand the opposing force produced by the

extending tip of a penetration hypha. When the hypha has penetrated the egg, it

rapidly destroys the juvenile within, before growing out of the now empty shell to

produce conidiophores and to grow towards adjacent eggs (Money, 1998).

Paecilomyces lilacinus has been reported to be very effective in controlling

root-knot nematodes viz., M. javanica (Hewlett et al., 1988; Freitas et al., 1995;

Ganaie and Khan, 2010), M. arenaria (Regina et al., 1991; Siddiqi et al., 2000), M.

hapla (DoChul and SangChan, 2004; Kiewnick and Sikora, 2006a) in different plants.

The management of root-knot disease on different crops caused by M. incognita by

using P. lilacinus has also been reported by many workers (Shahzad and Ghaffar,

1987, Sharma and Trivedi, 1989, Zaki and Maqbool, 1992, Sosamma and Koshy,

1997).

Cabanillas and Barker (1989) evaluated the impact of inoculum levels and

time of application of P. lilacinus for the control of root-knot nematode, M. incognita

on tomato. The best protection against M. incognita was attained with 10 and 20 g of

fungus-infested wheat kernels per microplot which resulted in a threefold and fourfold

increase in tomato yield, respectively, compared with tomato plants treated with this

nematode alone. Greatest protection against this pathogen was attained when P.

lilacinus was delivered into soil 10 days before planting and again at planting. Yield

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was increased twofold compared with yield in nematode-alone plots and plots with M.

incognita plus the fungus. Percentage of P. lilacinus infected egg masses were greater

in plots treated at midseason or at midseason plus an early application, compared with

plots treated with the fungus 10 days before planting and (or) at planting time.

Trivedi (1990) evaluated the fungus P. lilacinus for the biological control of

root-knot nematode, M. incognita on Solanum melongena. Better reductions in

gallings, final soil nematode population, number of eggs per egg mass were noted in

fungus inoculated plants.

Noe and Sasser (1995) evaluated the efficacy of P. lilacinus in controlling M.

incognita on four vegetable crops and soybeans under field conditions. Experiments

with tomato, okra, eggplant and pepper were carried out in two different sites. The

yield of vegetable crops in plots treated with P. lilacinus was higher than untreated

plots in both experimental sites. Cumulative yield data for okra and tomato showed a

widening difference between control plots and plots treated with fungus as the season

progressed and differences between treatments increased with each harvest date.

Similarly, M. incognita juvenile counts were lower in treated plots as compared to

control plots. The fungus provided the same level of nematode suppression as the

nematicide fenamiphos.

Jonathan et al. (1995) conducted experiments for two years with P. lilacinus to

control M. incognita infecting piper bettle. Rice grains infected with the fungus were

inoculated in different doses per plant and compared with carbofuran as control.

Better reduction of nematode population was observed in treating parasitic fungi

infested rice grains at 8 g/kg soil. The fungus penetrated the egg masses and the egg

masses contained empty egg shells.

Nagesh et al. (1997) conducted a field experiment for the management of root-

knot nematode M. incognita infecting tuberose (Polianthes tuberosa) by integrating

the use of the antagonistic fungus, P. lilacinus with leaf extracts of castor and neem as

bulb treatment and soil drenches. Combination of P. lilacinus with neem leaf extracts

resulted in significantly higher plant fresh weight and flower yield. Root gall index

was least under P. lilacinus plus neem leaf extract combination followed by P.

lilacinus plus castor leaf extract treatment. Although the per cent egg and egg mass

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parasitization by P. lilacinus was higher when integrated with the leaf extracts, neem

leaf extract improved the parasitization by P. lilacinus more than the leaf extract.

Bhat et al. (1998) studied the combined application of P. lilacinus and oil

cakes for protection of chickpea against M. incognita. The P. lilacinus at 5 or 10 ml

(3.5 × 107 spores/ml) differently limited the damage caused by M. incognita and

increased the plant growth and nodulation of chickpea. The best protection to

chickpea plants was obtained with 10 ml P. lilacinus spores. Neem and mustard oil

cakes at both 0.5 and 1.0 g/kg significantly suppressed the reproduction of M.

incognita and gall development and increased the growth and nodulation of chickpea

against M. incognita. The best protection of chickpea against M. incognita was

obtained with the combined application of P. lilacinus (10 ml) and neem cake (1.0

g/Kg).

Khan and Goswami (2000) evaluated the effect of different inoculum levels of

P. lilacinus, isolate 6 on M. incognita. All the treatments receiving P. lilacinus

showed significantly higher plant growth parameters than nematode alone. The gall

development and final nematode population in soil decreased with increasing doses of

P. lilacinus. The maximum population reduction was obtained at the higher doses of 8

and10 g. However, at these two doses, the final nematode population in soil did not

differ significantly. After analysing the data statistically and considering the various

growth parameters they proposed that 8 g fungus infested rice grains per kg soil was

optimum for suppression of M. incognita in tomato.

Dhawan et al. (2004) studied the efficacy of P. lilacinus against root-knot

nematode M. incognita infecting okra. The results showed that the application of P.

lilacinus as seed treatments @ 10, 15 and 20 g/ kg seed and soil application @ 1.5 and

3% w/w significantly increased plant growth characters of okra and suppressed galls,

egg masses/ plant and eggs/ egg mass. Of the two types of fungal applications tried,

soil application was found to be better in increasing plant growth characters and

reducing root-knot nematode population as compared to nematode alone treatment

Goswami et al. (2006) carried out an experiment to study the effect of two

fungal bioagents along with mustard oil cake and root-knot nematode M. incognita

infecting tomato. Bioagents viz., P. lilacinus and Trichoderma viride alone or in

combination with mustard cake and furadon promoted plant growth and reduced

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number of eggs/egg mass. The fungal bioagents along with mustard cake and

nematicide showed least nematode reproduction factor as compared to untreated

infested soil.

Kiewnick and Sikora (2006b) evaluated the fungal biocontrol agent, P.

lilacinus for its potential to control the root-knot nematode, M. incognita on tomato.

In growth chamber experiments, a pre-planting soil treatment reduced root galling,

number of egg and the final nematode population in the roots compared to the

inoculated control. Significantly dose-response relationships were established when

conidia were applied to soil either with or without the glucose-based formulation.

Sharma et al. (2007) conducted experiments under green house conditions in

earthen pots to manage M. incognita on okra with P. lilacinus alone and in combined

application with carbofuran, phorate and neem cake. It was observed that P. lilacinus

alone reduced the number of galls and ova per egg mass by 32% each and soil

population by 77%. The addition of carbofuran and phorate with P. lilacinus did not

further reduce the development and reproduction of M. incognita. The incorporation

of neem cake along with P. lilacinus improved upon the reduction of root-knot

nematode, the number of galls and egg masses. Plant growth parameters were better

in the neem cake treatment. Combining P. lilacinus, neem cake and chemicals did not

further reduce the root-knot nematode population significantly than the neem cake

alone.

Kumar et al. (2008) studied the effect of culture filtrates of P. lilacinus

isolates on the mortality and hatching of root-knot nematode, M. incognita. Culture

filtrates of all isolates of P. lilacinus showed toxic effect against M. incognita at

varying degree. Percentage mortality and hatching inhibition of M. incognita were

directly proportional to the concentration of culture filtrates and exposure period of

each filtrate. Rate of mortality was low in first 24 hrs but it appreciably increased with

the increase in exposure period. Similarly, different dilutions of fungal filtrates of all

the isolates were inhibitory to hatching to a varying degree. Isolate PIT-3 was found

to be more effective among all isolates in both mortality and hatching inhibition.

There was a relative decrease in the larval emergence with the corresponding increase

in the concentration of culture filtrates.

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Azam et al. (2009) reported that the plant growth of chickpea was enhanced

and the population of M. incognita reduced in the soil amended with P. lilacinus and

leaf powder of Cassia tora. The leaf powder when applied singly failed to reduce

final soil population of the nematode. Addition of P. lilacinus alone into the soil

reduced nematode population and increased yield of chickpea. The combination of

leaf powder of C. tora and P. lilacinus successfully managed the root-knot nematode

compared to individual inoculation of leaf powder of C. tora and P. lilacinus.

Sharma and Trivedi (2012) studied the effect of P. lilacinus by inoculating

different levels of nematode (500, 1000, 1500, 2000 J2s) infecting Vigna radiata.

Their results showed that P. lilacinus controlled the nematode population but increase

in initial population of nematode also increased the percentage of egg masses. They

also studied the influence of different levels of P. lilacinus (5, 10, 15 and 20 g) for the

management of M. incognita infecting V. radiata. All treatments infested with fungus

showed significantly higher yield as compared to control plants. Best results were

achieved when 20 g of P. lilacinus was used to check nematode.

Information on the role of Trichoderma species as bio-control agent for

controlling various fungal and plant parasitic nematode diseases has been reviewed by

Papavizas (1985), Spiegel and Chet (1998) and Pathak et al. (2007). The first

observable interaction between Trichoderma and its host is expressed by direct

growth of the mycoparasite hyphae towards the host, initiated by a chemotropic

reaction (Chet et al., 1981). The hyphae upon contact, coil around the host

(Benhamou and Chet, 1993), and penetrate its mycelium. This process involves the

release of lytic enzymes by Trichoderma which serve to partially degrade the host cell

wall (Elad et al., 1982; Chet et al., 1996). Trichoderma species have been shown to

induce phytoalexins production (Howell et al., 2000) and systemic resistance (Yedidia

et al., 1999) in the plants.

Rao et al. (1997) studied the effect of T. harzianum and neem cake alone and

in combination for the management of M. incognita on tomato. They found significant

increase in the plant growth and reduction in root galling and final nematode

population of M. incognita on tomato seedling grown in neem cake amended soil and

treated with T. harzianum.

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Khan et al. (2000b) reported that the T. harzianum and P. lilacinus showed

significant reduction in number of galls caused by M. incognita on tomato, followed

by tenekil as compared to control. Devi and Sharma (2002) studied the effect of T.

harzianum and T. viride @ 1g/kg soil against M. incognita on tomato. They reported

that both the treatments improved the plant growth and reduced the nematode

population. However, variation among the treatments was not significant.

Pandey et al. (2006) evaluated larvicidal, ovicidal and egg parasitisation

capacity of two fungal bioagents, T. harzianum and Aspergillus fumigatus against

root-knot nematode M. incognita infecting brinjal. They observed a significantly

remarkable reduction in M. incognita population in the treatments where both the

bioagents were used. They attributed that in the dual treatment, the toxic effect of A.

fumigatus killed a good number of infective juveniles in the rhizosphere while T.

harzianum parasitized the eggs inside the egg masses resulting in very poor nematode

population in brinjal.

Kumar and Khanna (2006) evaluated the efficacy of T. harzianum and neem

cake on tomato against M. incognita. The fungus was highly effective against M.

incognita when egg masses were inoculated 15 days prior to transplanting and fungus

at transplanting time in absence or presence of neem cake. This treatment when given

in neem cake amended pots resulted in better plant status than when given in pots

without neem cake.

Abd Al-Fattah and Sikora (2007) tested T. harzianum and T. viride for their

capacity to reduce the incidence and pathogenicity of the root-knot nematode, M.

incognita on tomato. In vitro studies demonstrated that all tested isolates were

effective in causing second-stage juvenile (J2) mortality compared with the control.

However, a slight increase in J2 mortality coincided with the use of T. harzianum

(Th3) when compared to the other Trichoderma isolates. Trichoderma slightly

reduced nematode damage to tomato in vivo. Treatment of the soil with the biocontrol

agents slightly improved nematode control when applied one week before

transplanting, but not at transplanting time. Only slight increase in plant growth could

be measured.

Goswami et al. (2008) conducted the experiments for the management of root-

knot nematode disease infecting tomato by the use of fungal bioagents, T. harzianum,

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Aspergillus niger and Acremonium strictum isolated from egg masses of M. incognita

infecting tomato. The rhizosphere and rhizoplane of root-knot nematode infested

tomato revealed consistent association of A. strictum. Aspergillus niger was

identified to be toxic against M. incognita, while, A. strictum and T. harzianum were

found to posses both egg parasitic or opportunistic and toxic properties. A field trial

with all the above fungal bioagents both alone and together showed significant

promising performance by the dual treatment of A. strictum and T. harzianum in

improving the health of tomato plant with a remarkable reduction in M. incognita

population.

Vinod and Jain (2010) evaluated some fungal and bacterial antagonists as seed

dressing treatment against root-knot nematode, M. incognita infecting okra. The seeds

of okra variety A-4 were treated with T. harzianum, T. viride and Pseudomonas

fluorescens each @ 10g/kg seed and carbosulfan 25 (DS) @ 3% a.i. (w/w) was also

included as treated check. The treated seeds were sown in root-knot nematode

infested soil having 2 J2/g soil. The observations recorded 45 days after sowing

indicated that the growth parameters of okra plants were better and root–knot

nematode populations were reduced in all the treatments compared to inoculated

control.

Jegathambigai et al. (2011) evaluated the efficacy of biocontrol fungi T.

harzianum and T. viride, against M. incognita infecting Livistona rotundifolia. In vitro

conditions revealed the nematicidal potential of selected T. viride and T. harzianum

for controlling M. incognita. The hyphae of Trichoderma penetrated and coiled the

female body. Eggs were also colonized and egg masses were penetrated by fungal

strands. Trichoderma viride and T. harzianum were able to colonize M. incognita

eggs and second stage juveniles and female. In vitro studies demonstrated that both

tested isolates were effective in causing nematode mortality compared with the

control. Under field conditions T. harzianum and T. viride in combination with cow

dung promoted plant growth, reduced number of galls/plant, females and egg

masses/root system. The Trichoderma sp. along with cow dung showed least

nematode reproduction factor as compared to untreated infested plant.

Affokpon et al. (2011) collected seventeen isolates of the free-living soil

fungus Trichoderma spp. from Meloidogyne spp. infested vegetable fields and

infected roots in Benin. All the isolates were screened for their antagonistic potential

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against root-knot nematode, M. incognita in greenhouse pot experiments on tomato.

In pots, a number of isolates provided significant nematode control compared with

untreated controls. They observed significant inhibition of nematode reproduction,

suppression of root galling and an increase of tomato yield compared with the non-

fungal control treatments. Trichoderma asperellum T-16 suppressed second stage

juvenile (J2) densities in roots by up to 80%. Tomato yields were improved by over

30% following the application of biocontrol agents, especially T. asperellum T-16.

2.8: Management approach by using organic amendments:

Plants are nature’s chemical factories which provide the richest source of

organic chemicals on earth. Plant derivatives possessing pesticidal properties are

gaining worldwide importance as an alternative or supplement for the existing

pesticides because of low cost, less environmental hazards and no risk of development

of resistance by the pathogens. The pest control properties of plants can be utilized

either directly by using plant tissues and/or dry powder, or crude derivative, such as

organic extract, or if possible through industrial process after isolation and

identification of the active compound/ compounds of plants (Grainge and Ahmad,

1988).

Organic amendments, including animal manures, compost and green manures,

are also commonly used in agricultural system to recycle nutrients and energy as well

as improve soil conditions for plant growth (Hader et al., 1992; Muchovej and

Pacovsky, 1997). Amendments provide energy and nutrients to soil, thereby

drastically changing the environment for the growth and survival of crops and

microorganisms (Drinkwater et al., 1995). Some organic amendments suppress

certain soil borne plant pathogens and/or the diseases they cause, and several have

been effectively used for control of plant-parasitic nematodes (Rodriguez-Kabana

1986; Alam 1990; Ali et al., 2001). Organic soil-amendments have been found to

effectively suppress the nematodes to varying extent depending upon the type of

organic matter, nematode, host plant species and the prevailing ecological conditions

(Sayre, 1971; Alam, 1976, 1990; Muller and Gooch, 1982; Badra et al., 1979).

Decomposition period of organic amendments play a key role in the nemato-toxicity

(Alam et al., 1982; Goswami and Vijayalakshmi, 1987). The decomposition of

organic matter helps in changing the physical, chemical and biotic conditions of soil

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which reduce the inoculum potential of the pathogens. In addition, it also improves

soil structure which enhances plant growth.

Linford et al. (1938) were the first to study the effects of chopped pine-apple

(Ananas comosum L.) leaves used as organic amendments against Meloidogyne sp.

Since then a number of plant species antagonistic to plant parasitic nematodes have

been discovered like Calotropis spp. (Ramanpreet et al., 2001; Saravanapriya and

Sivakumar, 2003), Crotalaria spp. (Yuhara, 1971; Subramaniyah and Yadivelu,

1990), Datura spp. (Gupta and Ram, 1981; Rao et al., 1986), Argemone mexicana

(Alam, 1986; Shaukat et al., 2002), Ricinus communis (Dutt and Bhatti, 1986; Patel et

al., 2004), Azolla pinnata (Thakar et al., 1987), Tagetes spp., (Sellami and Zemnouri,

2001; Meena et al., 2010), Azadirachta indica (Akhtar, 1998; Javed et al., 2008;

Ahmad and Siddiqui, 2009), Eucalyptus spp. (Abid et al., 1997; Dawar et al., 2007)

Calotropis procera (Zareena and Khan, 1984; Mukhtar, 1991; Ahmad et al., 1991)

Cassia spp. (Azam et al., 2009), and Lantana camara (Patel et al., 2004; Ahmad et

al., 2010)

Akhtar and Alam (1990) showed that bare-root dip treatment of tomato

seedlings with undecomposed and decomposed extracts of castor cake and leaves

significantly reduced root-knot development in pre-infected seedlings and in those

which were inoculated with 2nd stage juveniles of M. incognita after dip treatment.

Suppression of root-knot development was greater in pre-infected seedling than in

those inoculated after dip treatment. Oilcake extracts were more effective than leaf

extracts and decomposed extracts more effective than undecomposed extracts.

Further, severity of infection decreased with the increase in concentration of extracts.

Qamar et al. (1993) studied the nematicidal effect of some leaf extracts from

Eucalyptus citriodora (Hook), Azadirachta indica (A. Juss) and Withania somnifera

on nematode population, growth and yield of maize (Zea mays) in microplots.

Preplantation soil samples were collected and mean population of nematodes per 100

ml of soil extract was calculated. After 12 weeks, nematode population was

suppressed by 42.10% in the plants treated with E. citriodora, 41.0% in A. indica and

28.28% in W. somnifera treated plants. Weight of roots and shoots was maximum in

the plants treated with neem extract compared with control.

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Akhtar (1998) tested the neem leaf powder, sawdust and oilseed cake, and

urea for their activities against plant-parasitic nematodes (Hoplolaimus indicus,

Helicotylenchus indicus, Rotylenchulus reniformis and Meloidogyne incognita

juveniles), a predatory nematode (Dorylaimus elongatus), free-living nematodes and

the growth of chickpea, Cicer arietinum in the field. All the treatments resulted in

increased fresh and dry weights and the height and number of pods on chickpea

plants. The addition of oilcake, sawdust and leaf powder of neem significantly

reduced the population densities of plant-parasitic nematodes relative to control plots.

Oilcake was most effective, though all the neem products and urea markedly

suppressed plant-parasitic nematodes. However, leaf powder increased populations of

predatory and free-living nematodes. In general, greatest reduction in plant-parasitic

nematode populations was observed with oilcake followed by leaf powder, sawdust.

Rao et al. (1999) reported that the bare root-dip treatment of tomato seedling

in R. communis leaf extract mixed with P. lilacinus spores significantly increased the

tomato growth parameters, reduced the gall index and nematode population in

comparison to the C. procera leaf extract + P. lilacinus and P. lilacinus alone

treatments. Castor leaf extract both at 5 and 10% significantly increased mycelial

growth, sporulation and propagule density of P. lilacinus on roots resulting in

increased colonization of the bio-agent on the tomato roots offering enhanced

biological protection with the consequent effect of increased parasitisation of eggs of

M. incognita.

Walia et al. (1999) observed that the addition of chopped fresh leaves of

castor, eucalyptus or neem enhanced growth of okra with or without M. incognita.

The addition of P. lilacinus without plant leaves increased plant dry weight and

reduced root galling. However, the effect of the fungus was not discernible in pots in

which plant leaves were also incorporated. The impact of the fungus was evident by

increased dry shoot weight in the presence of castor leaves only. Among the plant

leaves, castor was most effective in suppressing root galling. With eggs as inoculum,

plant leaves alone failed to reduce the final juvenile population in soil, however, in

combination with the fungus, it was significantly reduced. When juveniles were used

as inoculum, the fungus was not effective, while plant leaves reduced their final

population to below a detectable level. In a field trial involving the use of castor

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leaves and P. lilacinus on tomato, maximum increase in yield was recorded with the

addition of leaves at 6 kg/m².

Cannayane and Rajendran (2002) evaluated 10 plant species viz., Abrus

precatorius (seed), Annona squamosa (leaf), Bauhinia scandens (leaf), Carica papaya

(leaf), Eucalyptus globules (leaf), Phyllanthus niruri (leaf), Tagetes erecta (root),

Tamarindus indica (seed), Thuja orientalis (leaf) and Vites negundo (leaf) for their

nematotoxic effect on egg hatching and second stage juveniles of M. incognita Race-3

under laboratory conditions. The extracts were prepared in 80% ethanol and tested at

4 different concentrations (20, 40, 60 and 80%) at 3 time intervals (3, 6 and 9 days for

the inhibition of egg hatching and 12, 24 and 36 h for juvenile mortality). The extracts

of A. squamosa, T. erecta and B. scandens exhibited a higher degree of nematicidal

effect by inhibiting egg hatching and juvenile mortality of M. incognita. The study

markedly revealed a linear relationship between the concentration of plant extracts

and the number of eggs hatched. Mortality of juveniles was directly proportional to

the concentration of plant extracts and period of exposure.

Sharma and Trivedi (2002) tested fresh leaf extracts of 15 plants viz., Datura

stramonium, Calotropis procera, Verbesena enceloides, Parthenium hysterophorus,

Morus alba, Phyllanthus amarus, Eichhornea crassipes, R. communis, Jatropha

curcas, Azadirachta indica, Tinospora cordifolia, Clerodendron multiflorum,

Catharanthus roseus and Adhatoda vesica against root-knot nematode, M. incognita.

Amongst the fifteen plants tested, leaf extracts of almost all the plants exhibited a

gradual increase in hatching of eggs from their higher concentration to lower

concentration treatments. Complete inhibition of hatching was observed in the highest

concentration in A. indica after 72 hrs and in C. procera after 24 hrs. Maximum

inhibition of hatching was recorded in C. procera and R. communis.

Saravanapriya et al. (2004) screened the nematicidal properties of 15 plant

products viz., Albizzia amara, Aristalochia bractiata, Tagetes erecta, T. patula,

Origanum magorana, A. indica, Butea monosperma and Calotropis gigantean leaves;

Acorus calamus roots; Allium sativum bulbs; Citrullus lanatus, Areca catechu and

Anona reticulate seeds and Calotropis gigantea and Carica papaya latex against egg

hatching of the root-knot nematode, M. incognita. The seed extracts of A. catechu

showed the highest inhibition in hatching at 0.1% concentration. The latex of C.

Papaya caused 98.22 and 100% hatching inhibition at 1.0 and 10.0% concentrations,

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respectively. The latex of C. gigantea also caused 100% inhibition at 10.0%

concentration.

Sahoo et al. (2004) studied the comparative efficacy of different locally

available organic/inorganic materials viz., fresh leaves of acacia, eucalyptus and neem

each @ 5 t/ha, neem cake @ 2 t/ha, lime, silkworm litter, simaruba seed powder each

@ 2.5 t/ha under field conditions. They reported that all the treatments significantly

reduced the root-knot index and improved the yield. Carbofuran recorded lowest root-

knot index, which was at par with the application of neem cake closely followed by

the application of fresh neem leaves and silk worm litter. Highest yield was also

obtained from carbofuran treated plots, which was at par with neem cake and neem

leaves.

Rajendran and Saritha (2005) studied the effect of Arnica montata, Calendula

officinalis, Carica papaya and A. indica plant extracts against M. incognita infesting

tomato. They reported that all the plant extracts reduced the root galls and nematode

population in soil. Maximum mortality was recorded in plants treated with A. indica.

Bhosle et al. (2006) studied the efficacy of organic amendment for the

management of root-knot nematode M. incognita infecting okra. They observed that

there was significant reduction in root-knot disease incidence and improvement in

plant growth characters by the application of groundnut cake (2.5 q/ha), sawdust, coal

ash (50 q/ha) and sunflower cake (2.5 q/ha).

Saikia et al. (2007) studied the efficacy of organic amendments viz., neem

cake, vermicompost, neem seed kernel, sawdust and carbofuran against root-knot

nematode, M. incognita in brinjal under field condition by applying individually and

in combinations. All the treatments showed significant effects on plant growth

parameters and yield of brinjal with the decrease in the nematode populations both in

soil and roots. Among all the treatments, the treatment with neem cake + carbofuran

showed superior over control in respect of plant growth parameters and yield of

brinjal and decrease in nematode multiplication.

Olabiyi (2008) studied the aqueous leaf extracts of weeds namely Sida acuta,

Euphorbia hitra, Andropogon gayanus, Phyllanthus amarus and Cassia obtusifolia on

the survival of second stage juveniles of M. incognita under laboratory conditions.

The results indicated that M. incognita juvenile mortality rate increased with an

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increase in test plant extract concentration and exposure time. In 15 and 20% (W/V)

concentration of E. hitra, P. amarus and C. obtusifolia and 20% (W/V) concentration

of S. acuta and A. gayanus there was 100% M. incognita juvenile mortality by 7th

day.

Ahmad and Siddiqui (2009) under greenhouse trials evaluated the effect of six

organic additives and nematicides viz., chopped neem leaves, chopped ficus leaves,

fresh cow dung, NPK fertilizers, phorate (Thimet 10G) and carbofuran (Furadan 3G)

on M. incognita infecting tomato. They observed that all the treatments stimulated

plant height, fresh and dry weights and fruit weight compared to untreated inoculated

plants. Plants treated with carbofuran were the best followed by phorate, neem leaves,

NPK fertilizers, ficus leaves and fresh cow dung. Application of organic additives and

nematicides also suppressed pathogenic effect and resulted in significant reduction in

gall index and population density of M. incognita in roots and soil. The highest

reduction in root-knot index was noted in plants treated with carbofuran, whereas the

lowest reduction was observed in plants treated with fresh cow dung.

Kayani et al. (2012) assessed the nematicidal potential of two antagonistic

plants Cannabis sativa and Zanthoxylum alatum Roxb. against the root-knot

nematode, M. incognita infecting cucumber (cv. Royal Sluis). The leaves of C. sativa

and Z. alatum were incorporated in the soil at the rate of 0, 2, 4, 6, 8, 10 and 20 g per

kg of soil. Both the plants, significantly reduced nematode infestations and enhanced

plant growth as compared to untreated check. The reduction in number of galls, egg

masses, nematode fecundity and build up caused by C. sativa were significantly

higher as compared to Z. alatum. Maximum reductions in these variables were

recorded with 20 g dosage.

Singh et al. (2012b) evaluated the effect of plant extracts viz., A. mexicana, C.

procera, Launaea procumbens, and P. hysterophorus against M. incognita in

chickpea. They noted that egg hatching and mortality of larvae (J2) were inversely

proportional to extract concentration and exposure time. Larval mortality was highest

in L. procumbens followed by C. procera, A. mexicana and P. hysterophorus. The

lowest nematode population, highest plant growth was found in chickpea plants

treated with 50 g leaf extract of L. procumbens followed by C. procera, A. mexicana

and P. hysterophorus under field conditions. Growth of chick pea plants were also

found to increase with leaf extracts of plants. Nematode population in soil, root and

root-knot index were decreased with the application of all the leaf extracts.

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Mukhtar et al. (2013b) assessed effectiveness of aqueous extracts of C. sativa

and Z. alatum on hatching, mortality and infectivity of M. incognita at different

concentrations viz., S, S:1, S:5, S:10, S:25, S:50 and S:100. Both the plants, showed

significant effects on juvenile mortality and hatching inhibition in a dose-dependent

manner. Mortality and hatching inhibition caused by C. sativa were significantly

higher than that of Z. alatum. Time duration also affected mortality and hatching

inhibition significantly. Significant inhibition in invasion of M. incognita juveniles on

cucumber cv. Royal Sluis was observed by different treatments with extracts.

Exposure for 12 and 6 h caused more than 95 and 90% reductions in infectivity of M.

incognita juveniles respectively. Similarly, soil drench and root dip treatments also

caused significant reductions in infection. Reduction in infectivity was found to be

significantly higher with extracts of C. sativa as compared to Z. alatum and decreased

in a dose-responsive manner.

2.9: Management of Disease complex:

Khan and Husain (1988a) studied the efficacy of seed treatments with

pesticides, oil-cakes, neem-leaf and P. lilacinus for the control of disease complex

caused by R. reniformis, M. incognita and R. solani. They observed that in case of

neem cake seed treatment there was significant improvement of plant growth only

when inoculated with M. incognita or R. solani individually or with all three test

pathogens. On the other hand seed treatment with groundnut-cake had no significant

beneficial effect on plant growth when inoculated with either of the nematode species

or all the three pathogens together but there was significant improvement in plant

growth when inoculated with R. solani. Neem-cake seed treatment significantly

reduced multiplication of both the nematode species when inoculated either

individually or concomitantly with the test pathogens. However, the seed treatments

with groundnut-cake did not significantly reduce the multiplication of either nematode

species. Neem-leaf seed treatment had no significant curative effect against any

pathogen.

Shahzad and Ghaffar (1989) evaluated the biocontrol potential of P. lilacinus

against the disease complex of okra and mung bean caused by soil borne fungus M.

phaseolina, R. solani and root-knot nematode, M. incognita. They observed that when

3 week old culture of P. lilacinus multiplied on rice grains, was applied to soil @

40g/m showed significant reduction in M. incognita root knot index on okra and mung

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bean as compared to control. Paecilomyces lilacinus reduced M. phaseolina

colonization of roots by 33% on mung bean and 45% on okra, whereas R. solani

infection was reduced by 67 and 73% on mung and okra, respectively. Furadan used

alone or in combination with P. lilacinus was less effective than P. lilacinus. Residual

effect of P. lilacinus was more than Furadan. A rice grain inoculum of P. lilacinus

showed better results as compared to its use on wheat straw, rice straw, sorghum

grains or as seed dressing.

Walia et al. (1994) studied the effect of green manuring on R. solani, R.

bataticola and M. javanica disease complex on tomato cv. HS-101 under pot

conditions. They reported that the plant growth was significantly increased in soil

amended with subabool and neem leaves compared with unamended control.

Meloidogyne javanica population, number of galls and egg masses was also reduced

in amended soil. Soil amendments with neem leaves decreased the incidence of both

R. bataticola and R. solani in the treatment where nematodes were inoculated one

week earlier than the treatment where R. solani was inoculated alone.

Mousa (1994) reported that the interaction of fungi (R. solani, F. oxysporum f.

sp. glycines and Sclerotium rolfsii) and the root-knot nematode M. javanica resulted

in a great deal of damage to soybean plants. He observed that Parmelierea sp. showed

the occurrence of higher inhibition zones with all pathogens followed by Bacillus

subtilis and Actinomyces griseus, while, T. harzianum showed significant parasitism

of these pathogens. A marked resistance of soybean plants to root-rot of R. solani and

S. rolfsii was observed when the biocontrol agents were introduced to the soil. The

symptoms of wilt on soybean almost disappeared in treatments with B. subtilis and T.

harzianum. The introduction of biocontrol agents to the soil one month before the

exposure to fungus-nematode, interaction resulted in significant reduction in disease

caused by the nematode.

Ehteshamul-Haque et al. (1995) studied the effect of pesticides viz., bavistin,

benomyl, topsin-M, captan and carbofuran and biocontrol agents viz., V.

chlamydosporium and P. lilacinus alone and in combination against M. javanica, R.

solani, M. phaseolina and F. solani disease complex on okra. They reported that V.

chlamydosporium, P. lilacinus, benomyl and topsin-M were more effective than

carbofuran against M. javanica when applied alone. V.chlamydosporium and

P.lilacinus also significantly reduced the infection of root infecting fungi viz., M.

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phaseolina, R. solani and F. solani as compared to untreated control. Combined use

of benomyl with topsin-M was found more effective in controlling infection of M.

javanica, M. phaseolina, R. solani and F. solani disease complex than the use of

carbofuran with fungicides. They also reported that all the fungicides reduced the

efficacy of biocontrol agents in controlling root-knot and root-rot infection on okra.

Ehteshamul-Haque et al. (1996) observed that the use of V. chlamydosporium,

P. lilacinus, Rhizobium meliloti or soil amendment with Stoechospermum marginatum

seaweed controlled the infection of M. javanica and M. phaseolina, R. solani and F.

solani infection of okra. Neem cake and datura powder were also effective against M.

javanica and M. phaseolina infection. The combined use of V. chlamydosporium and

neem cake completely controlled the M. javanica infection. The greatest height and

fresh weight of shoot were produced when R. meliloti was used with seaweed

followed by V. chlamydosporium used with neem cake.

Rekha and Saxena (1998) studied the biocontrol potential of T. roseum @ 1

g/kg soil and T. viride @ 5g/kg soil against R. solani and M. incognita complex on

tomato cv. Pusa Ruby under pot conditions and reported that both the biocontrol

agents reduced the harmful effects of R. solani and M. incognita and improved

germination significantly.

Parveen et al. (1998) evaluated the efficacy of Pseudomonas aeruginosa and

P. lilacinus for the control of root-rot and root-knot disease complex on some

vegetables. Pseudomonas aeruginosa and P. lilacinus used alone or together

significantly reduced infection of M. javanica root knot nematode and root infecting

fungi viz., M. phaseolina, R. solani, F. solani and F. oxysporum on pumpkin

(Cucurbita pepo), guar (Cyamopsis tetragonoloba), chilli (Capsicum annuum) and

watermelon (Citrullus lanatus). Pseudomonas aeruginosa was more effective than P.

lilacinus in reducing the M. javanica infection. Combined use of P. lilacinus and P.

aeruginosa was more effective in reducing the infection of root knot nematode in

guar, M. phaseolina and F. oxysporum on pumpkin and F. solani on guar and

watermelon than either used alone.

Siddiqui et al. (1999a) studied use of P. aeruginosa and fungal antgonists in

the control of root knot – root rot disease complex on mungbean and mashbean. They

observed that use of P. aeruginosa alone or in combination with fungi viz., V.

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chlamydosporium, P. lilacinus, Talaromyces flavus, T. harzianum and Stachybotrys

atra significantly reduced infection of M. javanica and root infecting fungi viz., M.

phaseolina, R. solani, F. solani on mungbean and mashbean. Soil treatment with P.

aeruginosa and V. chlamydosporium reduced gall formation mostly on mungbean,

whereas P. aeruginosa mixed with T. harzianum showed reduction in gall formation

on mashbean. Pseudomonas aeruginosa used alone or in combination with V.

chlamydosporium or P. lilacinus also significantly reduced egg mass production and

number of juveniles in soil, P. aeruginosa used with fungal antagonists also

significantly enhanced plant growth.

Siddiqui et al. (1999b) observed that root dip treatment with Pseudomonas

aeruginosa with or without T. harzianum, T. koningii and T. hamatum significantly

controlled infection of roots caused by F. solani, R. solani and the root-knot nematode

M. javanica on chilli. They further noted that combined use of T. harzianum with P.

aeruginosa caused the greatest reduction in gall formation by M. javanica.

Mehdi et al. (1999) studied the efficacy of leaves of Avicennia marina

(mangrove) with P. lilacinus for the control of root infecting fungi viz., R. solani, F.

solani, M. phaseolina and M. javanica under in vitro and green house conditions. Soil

amended with leaves of A. marina alone or in combination with P. lilacinus

significantly controlled root-rot, root-knot disease in tomato with enhancement in

plant growth and also increased the biocontrol efficacy of P. lilacinus in the control of

root pathogens.

Siddiqui et al. (2000) evaluated the efficacy of P. aeruginosa alone or in

combination with P. lilacinus for the control of root-knot nematode and root-infecting

fungi. They reported that P. lilacinus and P. aeruginosa significantly suppressed

soilborne root-infecting fungi including M. phaseolina, F. oxysporum, F. solani, R.

solani and M. javanica in tomato. Paecilomyces lilacinus parasitized eggs and female

of M. javanica and this parasitism was not significantly influenced in the presence

of P. aeruginosa.

Chaitali et al. (2003) reported that efficacy of groundnut cake and neem cake

at 5 per cent w/w and T. viride at 2 g mycelial mat of fungus per 500 g of soil for

control of disease complex caused by R. bataticola and M. incognita on okra. A

significant increase in plant growth parameters viz., shoot length, shoot weight, root

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weight and considerable reduction in nematode population observed on treatment with

neem cake alone followed by T. viride alone. However, treatment with groundnut

cake alone was found to be least effective

Lodhi et al. (2005) studied the comparative efficacy of P. lilacinus and

Talaromyces flavus on colonization of mungbean and soybean roots by M. incognita

and root infecting fungi viz., M. phaseolina, R. solani and F. solani. Soil amendment

with rice grain inocula of P. lilacinus and T. flavus showed a significant suppression

in colonization of mungbean and soybean roots by M. phaseolina, R. solani and F.

solani. The P. lilacinus also showed a reduction in root-knot index whereas, T. flavus

was ineffective. A combined application of both the biocontrol agents gave additive

effects against M. phaseolina and R. solani but not against F. solani and M. incognita.

Shresti (2005) studied the management of collar-rot complex caused by R.

bataticola, F. chlamydosporum and M. incognita in Coleus forskohlii using bioagents,

organic amendments and chemicals in different combinations. Combined application

of an organic amendment (Neemto) with a bioagent (T. viride) was found to be most

effective in reducing the wilt incidence, nematode population, number of galls and

colony forming unit of R. bataticola and F. chlamydosporum in coleus.

El-Nagdil and Abd-El-Khair (2008) tested T. harzianum, T. viride, Bacillus

subtilis and Pseudomonas fluorescens for managing M. incognita and R. solani both

in vitro and in the greenhouse conditions in comparison with the nematicide oxamyl.

The efficacy of the commercial product Micronema was assessed in the field. In vitro,

culture filtrates of B. subtilis, P. fluorescens, T. harzianum and T. viride at 10%

concentration caused nematode mortalities. The T. harzianum greatly reduced

mycelial growth of R. solani followed by T. viride, B. subtilis and P. fluorescens. In

the greenhouse the most effective culture filtrate applied as a soil drench was that of

B. subtilis at 10%, which reduced the number of juveniles in soil, galls and egg

masses of M. incognita on the roots of eggplant cv. Pusa Purple Long. The culture

filtrates of T. harzianum also reduced damping-off and root-rot incidence in

eggplants, followed by those of T. viride, P. fluorescens and B. subtilis. All bioagent

treatments improved plant growth and their effectiveness was similar to that of

oxamyl. In the field, Micronema protected eggplants from attack of M. incognita and

R. solani, thus increasing yield and affected populations of soil mycoflora differently

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Bhagawati et al. (2009) conducted an experiment under pot conditions to

manage the disease complex caused by M. incognita and R. solani on okra (Var.

Parvani Kranti) using T. harzianum and P. fluorescens. Both the bioagents were found

to be significantly effective in reducing the damage and increasing the growth

parameters of okra as compared to the treatment inoculated with M. incognita and R.

solani. However, seed treatments with either of the bioagents or both were found to be

more effective as compared to soil application in reducing the pre and post emergence

damping off, number of galls, egg masses and nematode population and increasing the

growth parameters which was comparable to the treatment with both the chemicals

viz., carbosulfan 25 ST and carbendazim 50% WP as seed treatment and un-

inoculated control.

Rizvi et al. (2012) evaluated the efficacious nature of some botanicals such as

A. mexicana, C. procera, Solanum xanthocarpum, and Eichhornia echinulata in

combination with normal as well as deep ploughing against plant-parasitic nematodes

and soil-inhabiting fungi infesting chickpea cultivar K-850 in relation to its growth

characteristics. Significant reduction was observed in the multiplication of plant-

parasitic nematodes, M. incognita, R. reniformis, Tylenchorhynchus brassicae, and

Helicotylenchusn indicus and in the frequency of parasitic fungi such as M.

phaseolina, F. oxysporum, R. solani, Phyllosticta phaseolina, and Sclerotium rolfsii

by the application of botanicals to soil. However, the frequency of saprophytic fungi

A. niger, T. viride, and P. digitatum was significantly increased. Much improvement

was observed in growth parameters like plant weight, per cent pollen fertility, pod

numbers, root nodulation, nitrate reductase activity, and chlorophyll content in leaves.

Jasim et al. (2013) studied the disease complex of M. incognita, R. solani and

Pythium aphenidermatum on tomato under greenhouse conditions. The fungal

pathogens @ 2x104 cfu/ plant and second stage juveniles of M. incognita @ 1020 /ml

of suspension were inoculated in the test plants. They observed that reduction in

various growth parameters increased when any of the three pathogen were inoculated

simultaneously as compared to when they were inoculated singly. The maximum

reduction was observed when M. incognita and P. aphenidermatum were inoculated

simultaneously followed by simultaneous inoculation of M. incognita and R. solani.

Further, maximum number of galls were observed on individual inoculation of M.

incognita.