PertanikaJ. Trap. Agric. Sci. 21(1): 1 -10 (1998) ISSN: 1511-3701© Universiti Putra Malaysia Press

Potential for Biological Control of Sclerotium Foot Rotof Chilli by Trichoderma spp.

J. JINANTANA and M. SARIAHI

Agricultural Research and Training CentreP.O. Box 89

A. Maung, 52000 Thailand

IDepartment of Plant ProtectionFaculty of Agriculture

Universiti Putra Malaysia43400 UPM Serdang, Selangor, Malaysia

Keywords: Sclerotium foot rot, chilli, organic fertilizers, Trichoderma harzianwn, T. virens

ABSTRAK

Penyediaan kering udara Trichoderma harzianum dan T. virens telah dinilai kemandirian danpotensinyasebagai calon kawalan biologi terhadap reput pangkal Sclerotium cili (Capsicum annuum L) sendirian atausebagai campuran dengan baja organik Amina, AVG'J'lti Greeen dan Greeen Supergrow sebagai pembawa. T.harzianum dan T. virens apabila dicampurkan sendirian dengan Amina dan Avanti Green masih kekalkebernasannya sehingga 180 hari tetapi apabila di campurkan dengan Green Supergrow hilang kebernasannyadengan cepat kepada sifar selepas 30 hari dalam simpanan. Kegiatan calon-calon Iwwalan biologi jugasignifikan dengan Amina apabila diuji dalam tanah yang diinoklat secara tiruan. Di ladang, penambahanpembawa organik hanya meningkatkan penetapan awal calon-calon Iwwalan biologi. Kejadian reput pangkalSclerotium berlmrangan dengan bererti dengan pengurangan sclerotia pathogen yang bernas dan pengasingansemula calon-calon kawalan biologi dalam rizosfera cli dan akar adalah tinggi T. Virens adalah calon yanglebih baik dengan memberi 100% dan 92.1 % pengawalan terlwdap reput pankal Sclerotium dalam tanahyang diinokulat secara tiruan dan tanah yang dijangkiti semulajadi berurutan.

ABSTRACT

Air-dried preparations of Trichoderma harzianum and T. virens were evaluated for their survival andpotential as biocontrol candidates against Sclerotium foot mt of chilli (Capsicum annuum, L) singly or asmixtures incorporated into organic fertilizers Amina, Avanti Green and Green Supergro as carriers. T.harzianum and T. virens incorporated singly into Amina and Avanti Green nmwined viable for 180 days butwhen incorporated into Green Supergro lost viability rapidly to zero after 30 days' storage. The performance of thebiocontrol ca'ndidates was also significant with Amirla when tested in the artificially-inoculated soils. In the field,the incorporation of an organic carrier only improved initial establishment of the biocontrol candidates. Theincide'nce of Sclerotium foot rot was significantly reduced with the reduction in the viable sclerotia of thepathogen and recovery of the biocontrol candidates in the chilli Thizosphere and mots was high. T. virens wasa better candidate, giving 100 and 92.1 % contml of Sclerotium foot mt in the artificially-inoculated andnaturally - infested soils respectively.

INTRODUCTION

Sclerotium rolfsii SacCo is one of the mostdestructive pathogens of chilli (Capsicum annuumL). Various strategies for controlling S. roifsiihave been introduced over the years includingsoil disinfestation, cultural practices and

fungicide treatments but losses still occur, largelybecause the effectiveness of these approaches isvariable and short lived. In addition, chillicultivars with strong resistance to S. roifsii arenot commercially available. As a result, researchefforts are directed toward developing effectiveand environmentally safe means of combating

J. JINANTANA AND M. SARIAH

foot rot of chilli. Indigenous isolates of Trichodermaharzianum and T. virens (= Gliocladium virens) havebeen identified as potential biocontrol agents foruse against S. rolfsii Qinantana and Sariah 1993,1997). However, applications of these biocontrolagents have been difficult, mainly because theirefficacy not only requires an excessively largeamount of inoculum but also varies with soil typeand environmental conditions.

Recent advances in our understanding ofthe infection mechanism of S. rolfsii on chillihave led to the conclusion that the target sitesfor infection are the stem collar andunderground stem Qinantana and Sariah 1994).Accordingly, the biocontrol agent should beplaced near the collar region of the chilli plantin order to achieve satisfactory control.Application of the biocontrol agent to soilmixture in nursery bags may assist in the earlyestablishment of the biocontrol agent aroundthe collar region before plants are transferred tothe field.

The present study attempted to evaluate theshelf-life of air-dried T. harzianum and T. virensindividually and as mixtures incorporated into 3types of commercially available organic fertilizerswidely used by chilli growers. The potential ofthe biocontrol preparations was also evaluatedfor the control of Sclerotium foot rot of chilli.

MATERIALS AND METHODS

Fungal Cultures

T. harzianum (IMI 378843) and T. virens (IMI378842) isolated from parasitized sclerotia andconfirmed to have antagonistic properties againstS. rolfsii Qinantana and Sariah 1993, 1997) weremaintained on potato dextrose agar (PDA) asthe biocontrol candidates tested in this study.

Prepa ration of Inoculum

The inoculum of the biocontrol candidatesconsisted of hyphae, conidia and chlamydosporesgrown on wheat grains. Three hundred grams ofcommercial wheat grains were soaked in waterfor 3 h, rinsed and autoclaved at 103 kPa twicefor 30 min in 100 ml of distilled water. Mtercooling, four 5-mm diameter discs from themargin of a 4-day-old colony of the candidateisolate growing on PDA were transferred to thewheat grain preparation and incubated for 14days at room temperature (28°C). Thepreparation was then ground and air-dried at28°C for 48h. Colony forming units (cfu) per g

air-dried preparation were determined bydilution plate technique on Trichoderma mediumE (TME) (Papavizas 1981).

Preparation of Dried Formulation

The air-dried biocontrol preparations wereincorporated into each of the three commercialorganic fertilizers (Table 1) in the ratio of 1: 5wlw (biocontrol candidate: organic fertilizer)and kept in sealed polythene bags. For themixture, T. harzianum and T. virens were mixedin equal proportions before adding to each ofthe organic fertilizers. The biocontrol-fertilizerpreparations were stored at room temperature(28 ± 2°C) in a completely randomized designwith 3 replications. Samples (1 g) were takenfrom each replication at 0, 30, 60, 90, 120, 150and 180 days and the rate of survival andproliferation of the biocontrol candidates weredetermined by dilution plate technique. Thedata were expressed as cfu per g air-driedbiocontrol-fertilizer preparation. Data werestatistically analysed by ANOVA and meanscompared by using Duncan's multiple rangetest.

Application of Biocontrol Candidates and Rating ofDisease in Sclerotium-chilli System

Glasshouse trial: Potting medium was prepared bymixing sterilized soil mixture (3 : 2 : 1 vIvmixture of soil, sand and organic matter) withthe respective biocontrol preparations. For eachorganic carrier evaluated, treatments consistedof organic fertilizer alone; amended with eachair-dried biocontrol candidate (2-weeks-old driedformulation) or mixtures of the biocontrolcandidates at 0.08% and 0.05% (w/w)respectively. Four hundred grams of each mixturewere placed in pots, sampled and assayed forinitial population densities of the biocontrolcandidates. Soil mixture alone was also used asthe control. One-month-old chilli seedlings weretransferred to each of the pots and maintainedin the glasshouse for 28 days with normalwatering.

These plants were then transferred tosterilized soil mixture which had been artificiallyinoculated two weeks earlier with 4-week-old S.rolfsii inoculum raised on wheat grains at a rateof 3% w/w. There were 24 plants in eachtreatment. The treatments were arranged incompletely randomized design.

2 PERTANlKAJ. TRap. AGRIC. SCI. VOL. 21 NO.1. 1998

'"t'I'l~~~

~;0;>o~oeno<::or~......z9............<.0<.000

~

TABLE ITrade name, formulations and compositions of the commercial organic fertilizers used in the study

Organic fertilizer Trade name Formulation Application Organic Total N21 Avail. p:{1 Avail. KII pHrate for chilli matter ll (%) (%) (%)

Tapioca organic fertilizer Amina 5.5:5.5:5.5:5.1 +TE Not labelled 10.69 4.70 1.64 0.03 6.80

Oil palm organic fertilizer Green Supergro 5 : 5 : 5 : 1 +TE Not labelled 20.61 4.89 1.81 0.04 3.48

Chicken dung organic Avanti Green Not labelled 40 kg/l00-200 m2 21.47 1.41 0.71 0.03 5.97fertilizer

II analytical analysis by Walkly and Black Method (Nelson and Sommers 1982)2/ analytical analysis by Micro Kjeldahl method (Bremmer and Mulvaney 1982)~I analytical analysis by Bray II method (Bray and Kurtz 1945)11 analytical analysis by lIsing NH4AC (pH 7.0) (Anon. 1996)

Moisturecontent

(%)

18.52

25.08

18.74

'"o~t'I'lZ::l;>~

'"rj

o::0to(3

5o§~

no~f5~

o'"rj

V:

B~"""".....;

~"'"'"rj

oo~

::0o~

o'"rj

n::r:

E~""""~

i>~en

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.J. JINANTANA AND M. SARIAH

The number of infected (wilting with whitemycelium at the collar) chilli plants wasdetermined 28 days after transplanting to theSclerotium infested soil. Determination of thepopulations of the biocontrol candidates in thechilli rhizospheres (within 5-cm radius from thestem and 10-cm depth) and on the roots wascarried out 20 and 40 days after transplanting.Soil and roots were sampled, homogenized andplaced on a shaker for 20 min in sterilizedwater. The homogenate was serially diluted withsterile water. One-ml aliquotsof the dilution(10-1) was spread with a glass rod over the surfaceof the agar plate containing TME, and incubatedfor five days in the dark, after which typicalgreenish colonies were counted. Similarly,populations of surviving S. rolfsii propagules wereassessed following the method of Rodriquez­Kabana et al. (1980).

Field Trial: The organic fertilizer Amina waschosen as the carrier for the biocontrolcandidates based on the results of the survivaland glasshouse evaluation trials. The preparationof the seedlings was similar to that used in theglasshouse trial. There were eight treatments(Table 5), arranged in randomized completeblock design with three replicates; each replicateconsisted of two rows and each row comprisednine chilli plants. The initial population ofSclerotium propagules in the experimental plotswas determined.

Six-week-old chilli plants previously o-rown. bIII the nursery bags containing differentbiocontrol-amended and non-amended(fungicide and control) soil mixtures weretransplanted to the naturally infested field. Forthe fungicide treatment, 500 ml of aqueousBrassicol suspension (200 mg a.i./l H

20) was

applied to each plant by drenching soon aftertransplanting. Watering, fertilization and pestcontrol were as recommended for chillicultivation in the area. No fungicide wassubsequently used. The number of chilli plantsinfected was assessed two and four months aftertransplanting. Determination of the populationsof biocontrol candidates and S. rolfsii in the soilaround the chilli rhizospheres (within 5-cmradius from the stem and 10-cm depth) wasdetermined 1, 2 and 4 months after the plantswere transferred to the infested fields.

RESULTS

Survival of Biocontrol Candidates

T.he survival of air-dried biocontrol propagulesdIffered with the organic fertilizer used as carrierresulting in different shelf-lives of each biocontroipreparation. T. harzianum and T. virens singly oras mixtures incorporated into Amina and AvantiGreen had a significantly longer (P< 0.01) shelf­life than those incorporated into Green Supergro(Table 2). The population levels of both ftmo'i

b

~ropped to zero within 30 days of incorporation~nto Gr~en Supergro while those incorporatedmto Amma and Avanti Green could be detectedfor 180 days and 120 days for T. harzianum andT. virens respectively, after storage at roomtemperature (28 ± 2°C). Amina and Avanti Greensupport significantly higher numbers of viableT. harzianum propagules than T. virens durino'storage. This was further observed when bothbiocontrol candidates were used as mixtures,the majority of the biocontrol populationrecovered was that of T. harzianu'/7/, rather thanT. virens.

A~plicat~on of Biocontrol Candidates and Rating ofDzsease zn the Sclerotium-chilli System

The biocontrol candidates parasitized thesclerotia of S. rolfsii, resulting in the failure ofthese sclerotia to germinate when plated onPDA Uinantana and Sariah 1997). The numbersof viable sclerotia per 100 g air-dried soil sampledfrom the respective treatments were significantlylower (P < 0.01) than those taken from the.control at 3 and 40 days after transplanting(Table 3). The lowest number of viable sclerotiawas achieved by treatments of biocontrolcandidates with Amina and hio-hest when, b

mcorporated into Green Supergro at day 3, butall treatments were equally as good at day 40.

The incidence of Sclerotium foot rot on chilliplants was evaluated 20 days after transplantino-.T. virel1s, either singly or incorporated too-eth;r'h bWIt the organic fertilizers, gave 100% control of

the disease. However T. harzianu'1Jl, supplementedwith Amina only gave 83.3% reduction in diseaseincidence (Table 3). The sio'nificant reduction. b

m foot rot of chilli was due to the hio-her initial. b

populatIons of the biocontrol candidates in therespective treatments and these populations weremaintained throughout the experiments as showi1by samplings made after 20 and 40 days after

4 PERTANlKA.J. TRap. AGRIC. SCI. VOL. 21 NO.1, 1998

* Means in the same column with different letters are significantly different (p<.Ol) using DMRTTh = T. harzianum Tv = T. vi1'ens

TABLE 2Populations of air-dried T. harzianum, T. virens and T. harzianllm + T. virens culture incorporated into

the organic fertilizers and stored at room temperature for 0-180 days

8.4xlO j b 4.0xl02 c 2.4xl02 b 2.3x102 a 2.2xl02 a 8.8xlO I b2.9xlO j

C 4.0xl02 c 0.6xl02 d O.lx 102 c 0.0 C 0.00 b3.7xlO j

C 4.6xl02 ab 1.5xlO~· c 0.lxl02 c 0.lxl02C 0.00 b

Th=2.5xlO j Th=2.3xl02 Th=l.2xl02 Th=0.lxl02 Th=0.lxl02

Tv =l.2xlO j Tv =2.3xl02 Tv =0.3xl02 Tv =0.03x102 Tv =0.0

10.7xlOj a 4.2xl02 bc 3.0xl02 a 2.4xl02 a3.6xlOj c 4.2xl02 bc 0.9xl02 d 0.lxl02 c3.1xlO j c 4.9xl02 a l.5xl02 c 1.4xl02 bTh=2.0xlO j Th=2.5 xl02 Th=l.2xl02 Th=l.3xl02

Tv =l.lxlO j Tv =2.4xl02 Tv =0.3xl02 Tv =0.lxl02

0.0 d 0.0 d 0.0 e 0.00 c0.0 d 0.0 d 0.0 e 0.0 c0.0 d 0.0 d 0.0 e 0.00 c

....::~

~:::r::a

~:;;..s:CJl'ij

~

'ij

o....,tT1Z....,;;l'

b::0tool'o()

~()oz....,::0ol'

o'Tj

Cr.

~~....::~

~'Tj

oo....,::0o....,o'Tj

():r:Ft:to-<

180 Days

0.0 b0.0 b0.0 b

10.8xlO I a0.9xlO I b0.0 b

0.0 c0.0 c0.0 c

l.5xl02 b0.lxl02 C

0.lxl02 C

Th=0.lxl02

Tv =0.0

150 Dayscfu per g air-dried preparation

60 Days 90 Days 120 Days30 Dayso Day

0.2xlO I' C

O.lxlO H C

0.2xlO I" C

Th=O.lxlO l'Tv =O.lxlO '·!

l.6xlO H a*l.4xl014 al.OxlO I ! bTh =0.6xlO I'Tv =O.4xlO H

1.6xlO l1 a1.5xlO l1 a0.8xl0 11 bTh=0.5xlO '1

Tv =0.3xlO H

T. harzianum + AminaT. virens + AminaT. harzianum + T. virens + Amina

Biocontrol preparations

T. harzianum + Avanti GreenT. virens + Avanti GreenT. harzianum +T. virens + Avanti Green

T. harzianum + Green SupergroT. virens + Green SupergroT. harzianum + T. virens + GreenSupergro

.......

~<.000

z9

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.J..JI ANTANA AND M. SARIAH

TABLE 3Number of viable Sclerotia and percentage of surviving plants from the artificially-inoculated soil

Treatmen ts

T. harzianu1n + AminaT. harzianll1n + Green SupergroT. harzial1ll1n + Avanti GreenT. harzianwJl

T. virens + AminaT. virens + Green SupergroT. virens + Avanti GreenT. vnens

T. har:.imllllll + T. virens + AminaT. har:ianlllll + T. virens + Green SupergroT. harzianu1ll + T. virens

T. har:.wnum + T. virens

ControlSoil mixture alone

minaGreen SupergroA\'anti Green

Number of viable S. rolfsii propagules % Sun'i\'ingper 100 g air-dried soil Plants

3 Days 40 Days 20 Days

5.0 c* 2.3 b 83.3 a18.0 b 4.6 b 61.1 b8.3 c 2.6 b 77.7 ab5.6 c 3.0 b 77.7 ab

2.6 c 2.3 b 10013.0 b 3.3 b 10011.0 b 3.0 b 10011.0 b 3.0 b 100

5.6 c 2.:1 b 100

3.3 c 1.6 b 1003.3 c 1.6 b 100

73.3 a 58.3 a 072.0 a 60.1 a 070.8 a 59.4 a 072.5 a 60.6 a 0

* Means in the same column of each group of dta with different letters are significantly different (p<O.l) usingDMRT

transplanting and also on the root rhizosphere(Table 4) . Cfu of T. harzianum recovered fromthe soil was reduced whereas that of T. virensincreased. Amina enhanced the survival andproliferating ability of T. virens in the chillirhizosphere. The population of biocontrolisolates recovered from roots was higher thansoil rhizospheres with respect to the differenttreatments analysed.

Field trial: T. harzianum and T. vzrens in allpreparations with Amina as the carrier or singly,and Brassicol significantly reduced the populationof sclerotia in the infested soil as compared tocontrol (Table 5). The symptoms of Sclerotiumfoot rot were observed two months aftertransplanting. Symptoms appeared as wilting withthe production of white rhizomorphs at the baseof the stems. T. virens-organic carrier and T.virens alone gave highest percentages of survivingplants compared to T. harzianum or the control(Table 5).

The initial populations of the biocontrolcandidates in the soil were assessed in the nursery

bags one week after amendment, prior totransplanting and subsequently 1, 2 and 4 monthsafter transplanting. It was found that there weresignificant differences (p<O.O 1) in thepopulations among the treatments (Table 6).Results showed that within one month aftertransplanting, populations of T. virel/s whenapplied singly had increased from the numberfound prior to transplanting to the infestedfield, while the population of T. harzia17umdecreased, suggesting that T. virens wassustainable in the Sclerotium-infested soil.

DISCUSSION

T. harzianu'lll and T. virens isolates evaluatedhave been proven to effectively parasitizemycelium and sclerotia of S. mlfsii Qinantanaand Sariah 1993, 1997) under laboratoryconditions, and their potential as biocontrolagents against Sclerotium foot rot on chilli hasbeen clarified in this study. Connick et al. (1990)have stated that a successful biocontrolformulation is one that is economically produced,safe and stable in the environment, easily applied

6 PERTANlKA.J. TROP. AGRIe. SCI. VOL. 21 NO.1, 1998

POTEI'\TIAL FOR BIOLOGICAL CONTROL OF SCU~RUnUMFOOT ROT OF CHILLI BY 'fRlCHOJ)U?MA SPP.

TABLE 4Populations of the biocontrol candidates in the artificially-inoculated soil

Treatmentscfu per g aOl'-dried soil (x10 1

) cfu per g air-drried root (x10')

T. harzianlllll + AminaT. har:.ianlllil + Green SupergroT. hm:ianlllll + Avanti GreenT. hal:ianlllll

T. virens + AminaT. vir-ens + Green supergroT. virens + Avanti GreenT. vnen5

T. h(l/:iml/llll + T. virens + Amina

T. IUI/:.iml/llll + T. virens +

Green Supergro

T. hm:.iartlil/l + T. virens +

Avanti Green

T. lwr:ianlllll+ T. vir'ens

In nursery bags In soil around the chilli plants on '"ootsinitiaJlI on transplanting:!! 20 Daill 40 Days~: at 40 Days~'

7,8 a* 5.9 a 0.7 a 0.7 a 2.0 a2.9 b 0.4 c 0.6 a 0.0 c 1.6 b7.1 a 3.2 b 0.7 a 0.3 b 1.5 b4.3 b 0.9 c 0.7 a 0.3 b 1.5 b

1.2 a 0.7 a 3.1 a 6.8 a 9.5 a0.3 c 0.5 a 1.6 b 1.4 b 8.9 b0.8 b 0.6 a 1.9 b 5.8 a 1.3 d1.2 a 0.6 a 1.6 b 1.5 b 6.9 c

::$.1 a 1.2 a 2.3 a 3.5 a 7.4 aTh=2.2 Th=0.8 Th=O.3 Th=O.1 Th=23Tv=0.9 Tv=O.4 Tv=2.0 Tv=3.4 Tv=5.1

1.1 b 0.9 b 1.50 b 2.9 ab 6.2 bTh=0.6 Th=0.2 Th=0.2 Th=O.1 Th=1.8Tv=0.5 Tv=O.4 Tv=1.2 Tv=2.8 Tv=4.4

1.2 b 0.9 b 1.5 b 2.4 b 1.5 dTh=0.8 Th=0.5 Th=0.4 Th=O.l Th=O.9Tv=O.4 Tv=O.4 Tv=1.1 Tv=2.3 Tv=0.6

3.0 a 0.8 b 1.4 b 2.9 ab 4.0 cTh=2.1 Th=O.5 Th=O.2 Th=O.l Th=1.7Tv=O.9 Tv=O.3 Tv=1.2 Tv=2.8 Tv=2.3

* Means in the same column of each group of data with different letters are significantly different (P<OI)using DMRTTh = T. harzianulll Tv = T. vir-ens

I at 1 wk after amendment and prior to transplanting of the chilli into the bagson the day thc chilli plants \vere transferred to S. w(fsii-infected soil

:1 days aftcr transplanting the chilli to S. ro(fsii-infested soil

using conventional agricultural equipment andgives effective and consistent results under avariety of environmental conditions. Three typesof commercially available organic fertilizer(Amina, Green Supergro and Avanti Green)were tested as carriers for the biocontrolcandidates. Results showed that Amina wassuperior to the other two organic fertilizers asthe delivery system for the biocontrol candidatesin the glasshouse. The recovery of biocontrolisolates incorporated into Amina around theplant rhizospheres and roots was high, andviability of S. rolfsii propagules in the soil waslow, resulting in low incidence of Sclerotium foot

rot. However, in the field experiment, additionof Amina did not significantly reduce viability ofsclerotia compared to biocontrol alone, eventhough it improved the initial establishment ofthe biocontrol candidates in the ScleroliulJl,­infested soil.

Differences in effectiveness of differentorganic fertilizers used as carriers may haveresulted from the interaction between thebiocontrol candidates and chemical and physicalcharacteristics of the carriers (Table 1). Themoisture and nutrient content of the carrierspossibly affected the effectiveness of thepreparations in controlling diseases. Watanabe

PERTANIKAJ. TROP. AGRIe. SCI. VOL. 21 NO.1, 1998 7

.J. JINANTANA AND M. SARIAH

TABLE 5lumbers of viable sclerotia and percentage of surviving chilli plants in the naturally-infested field

Treatments

Number of viable S. rolfsii pripagules per100 g air-dried soil

% Survivingplants

T. har:ianu1Il + AminaT. virens + AminaT. harzian1l1ll + T. virens + AminaT. virens

T. halZian1l1ll

T. hmzianu1It + T. virens

BrassicolControl

initiaJlI

1413151614121317

1 month~1

5.0 bc*3.0 c6.6 b7.0 b6.3 b5.3 bc8.0 b

16.0 a

2 months~1

3.6 bc2.6 c5.3 b5.3 b3.1 b5.3 bc5.6 b

14.3 a

4 monthsU

2.6 cd1.6 d3.6 bcd4.0 bc2.8 bc4.3 bc5.3 b

13.7 a

4 months~1

74.7 b92.1 a81.4 ab83.3 ab73.7 ab75.0 b69.9 bc58.3 c

* Means in the same column with different letters are significantly (P<O.l) using DMRTII 1 day prior to tranplanting of the chilli plants to the field~I after transplanting of the chilli plants to the field

TABLE 6Populations of the biocontrol candidates sampled from naturally-infested field

cfu per g air-dried (x10:l)

TreatmentIn nursery bags In soils around the chilli plants

initial'l on transplanting~1 1 month:l/ 2 months:l

' 4 months:ll

day

T. harzian1l1ll + Amina 5.2 a* 3.6 a 1.3 cdT. vir'ens + Amina 4.9 a 3.7 a 4.6 aT. harzianu1Il + T. virens 3.7 b 2.5 b 2.6 bc+ Amina Th=2.3 Th=1.3 Th=O.4

Tv=1.4 Tv=1.2 Tv~2.2

T. harzian1l11Z 4.8 a 2.7 b 0.9 dT. virens 3.1 c 2.7 b 4.1 abT. harzian1l11l + T. virens 3.2 bc 2.2 b 2.0 cd

Th=2.0 Th=1.3 Th=0.5Tv=1.2 Tv=0.9 Tv=1.5

1.1 de3.1 a1.8 bc

Th=0.2Tv1.6

0.7 c2.3 b1.3 cd

Th=0.2Tv=1.1

0.6 d2.3 a

1.3 bcThO.1Tv=1.2

0.3 d1.9 ab0.9 cdTh=O.lTv=0.8

Means in the same colimn with different letters are significantly different (P<Ol) using DMRTTh = T. harzian1l1ll Tv = virensII at 1 wk after amendment and prior to transplanting of the chilli into the bags~I on the day the chilli plants were transferred to S. mifsii-infested soil:ll months after transplanting the chilli to S. roifsii-infected soil

et at. (1987) found that nitrogen fertilizersstimulated growth and production of conidia ofTrichoderma in culture and may have a synergisticeffect on biocontrol ability. Soil condition isanother factor that could affect the availabilityof nutrients dissolved from organic fertilizers,thus influencing the proliferation and activity ofbiocontrol candidates. The efficiency ofbiocontrol agents have been related torhizosphere competence (Ahmad and Baker

1987a, b). The survival of Trichoderma in soils wasstudied by Papavizas (1981) who concluded thatthe antagonist did not survive well in therhizosphere. However, survival of the indigenousT. harzianum and T. virens isolates in the chillirhizosphere was significantly improved byincorporating into organic fertilizer in thedelivery system for early establishment althougheffect was diluted with time.

8 PERTANIKA.J. TROP. AGRIC. SCI. VOL. 21 NO.1, 1998

POTENTIAL FOR BIOLOGICAL CONTROL OF SCU~'IWTJUMFOOT ROT OF CHILLI BY TRICHOJ)J~RMA SPP.

The application of the biocontrol candidatesto control soil-borne diseases was mostly throughsoil amendments in which high quantities of thepreparations were needed. Seed treatment andapplication of the antagonist to rooting orseedling mixtures are alternative methods whichcould improve establishment and colonizationability in the plant rhizosphere. This will enhancethe effectiveness of disease control with the addedadvantage of using small volumes of biocontrolpreparations. Elad et al. (1981) applied T.harzianum to rooting mixture for carnation andfound that disease incidence due to Rhizoctonia

solani was decreased when the carnations withthe whole rooting mixture were transplanted toinfested soil. Chilli seedlings are normallyprepared in the nursery before being transferredto the field, thus application of the biocontrolformulation to soil mixture in the nursery bagswould be the best option. It was found in thepresent study that this approach providedeffective control of Sclerotium foot rot of chilliplants in the artificially -inoculated and naturally­infested soils.

Even though T. hmzianum and T. vire'l7s

possessed no inhibitory effect on each otherwhen used in combinations (Jinantana and Sariah1993; 1997), the effectiveness of the preparationwas mainly due to the activity of T. virens. Thiswas confirmed by the results of the recovery(cfu) of T. virens from soils with time ofapplication. Although T. harzianum survivedbetter in storage, its proliferation in the plantrhizosphere was poor, thereby making T. virens

a better candidate for the biocontrol of Sclerotium

foot rot. In addition, biomass of T. harzianum

and T. virens used for incorporation into thecarrier in the present study comprised mainly ofconidia and mycelia. It has been reported thatchlamydospores were more important thanconidia in survival and proliferation of thebiocontrol candidates (Lewis and Papavizas 1984;Beagle-Ristaino and Papavizas 1985 a, b).Therefore, using biomass comprising abundantchlamydospores of T. harzianum and T. vir'ens

incorporated into Amina may enhance furtherthe effectiveness of the biocontrol candidates incontrolling Sclerotium foot rot of chilli in Malaysia.

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(Received: 1 August 1997)(Acceflted: 6 August 1998)

10 PERTANlKA.J. TRap. AGRIC. SCI. VOL. 21 NO.1, 1998