international rice research newsletter vol.17 no.3

8/4/2019 International Rice Research Newsletter Vol.17 No.3

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IRRN GUIDELINES

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reports appropriate. adequate data

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Report appropriate statistical

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Categories of research published

GERMPLASM IMPROVEMENT

genetic resources

genetics

breeding methods

yield potentialgrain quality

pest resistance

diseases

insects

other pestsstress tolerance

drought

excess water

adverse temperature

adverse soils

irrigated

rainfed lowland

upland

deepwater

tidal wetlands

seed technology

CROP AND RESOURCE

MANAGEMENT

soils

soil microbiology physiology and plant nutrition

fertilizer management

inorganic sources

organic sources

integrated germplasm improvement

crop management

integrated pest management

diseases

insects

other pests

water management

farming systems

farm machinery

postharvest technology

economic analysis

ENVIRONMENT

SOCIOECONOMIC IMPACT

EDUCATION AND

COMMUNICATION

weeds

RESEARCH METHODOLOGY


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CONTENTS


Generic resources

5 The chromosome number of Oryza schlechteri Pilger

Genetics5 Combining ability of some rice genotypes for ratooning in diallel mating

system

Breeding methods

6 Influence of type of vessel on regeneration of rice anther calli

Yield potential

6 Agrophysiological differences between deepwater rice (DWR) and

rainfed lowland modern variety (MV) under farmers field conditions

Grain quality

7 Relation between rice grain quality and land preparation methods

7 Rice grain quality as influenced by split application of nitrogenous

fertilizer

Pest resistance diseases

7 A new symptom of tungro in rice

8 Resistance to rice tungro bacilliform virus (RTBV) found in wild Oryza

9 Performance of a bacterial blight (BB)-resistant rice variety in the

spp.

endemic pockets of Konkan Region, India

Pest resistance insects

9 Insecticide-induced resurgence of brown planthopper (BPH) on IR62

10 Genetic sources of resistance to whitebacked planthopper in scented

10 Screening Basmati rices for stem borer resistance

11 Effects of whitebacked planthopper (WBPH) Sogatella furcifera on rice

quality rices

varieties in the greenhouse

Pestresistance others pests

11 Assessment of rice resistance and susceptibility to stem nematode

Integrated germplasm improvement irrigated

12 Yield performance of some new rice hybrids in Indonesia

13 ZH3, a high-yielding and multiple-resistance rice for single- or double-

Ditylecnhus angustus

cropping in South China

Integrated germplasm improvement water

13 Three varieties of floating rice released to farmers in Cambodia

Stress tolerance

14 Weed competitiveness of upland rice cultivars in Bangladesh

CROP AND RESOURCE MANAGEMENT

Physiology and plant nutrition15 Sesbania rostrata and Aeschynomene afraspera effects on crop

15 Response to different Zn carriers of rice grown on Ustifluvents in India

establishment of transplanted lowland rice

Fertilizer management inorganic

16 Long-term effect of inorganic fertilizers, lime, and straw on lowland rice

16 Large granule urea (LGU), an efficient and economic source of N for

in Kerala

wetland rice

Crop management

17 Effect of herbage cutting on deepwater rice (DWR) in acid sulfate soil

Integrated pest management diseases

18 Growth and sclerotial production of Sclerotium oryzae on different

media

18 Effect of humic acid (HA) on severity of rice blast (B1)

19 Comparative transmission of three tungro isolates by green leafhopper

19 Dependence of incubation period and symptoms of rice tungro disease

(GLH)

(RTD) on infection stage in ricefields

Integrated pest management insects

20 Damage by rice thrips and defoliators in southern Bhutan

20 Effect of foliar spray insecticides on brown planthopper (BPH)

21 Hourly catches of yellow stem borer (YSB)

21 Effect of rice stage and GLH density on pipunculid parasitism on green

22 Evaluating high temperature tolerance in the brown planthopper (BPH)

23 Sheath rot (ShR) severity due to rice bug infection

Farm machinery

23 A simple closed chemical transfer attachment for knapsack sprayers

ANNOUNCEMENTS

resurgence in rice

leafhopper (GLH) Nephotettix virescens in Bali, Indonesia

24 Irrigation and drainage congress

24 Effective irrigation management course

24 New IRRI publications

24 New publications

25 Rice dateline

25 Call for news

25 IRRI group training courses for remainder of 1992

25 Postdoctoral research fellow positions

NEWS ABOUT RESEARCH COLLABORATION

26 Guidelines for contributors

26 A dream that might come true: rice plants that make their own fertilizer

26 Cambodia team identifies useful breeding lines

26 Rice Processing Working Group Meeting convenes in Egypt

27 IARCs and national systems seek alternatives to slash-and- burn farming

27 France, IRRI plan joint research for the next five years

27 Laser measures ricefield methane

27 Upland Rice Research Consortium contacts


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Genetic resources~

The chromosome number ofOryza schlechteri Pilger

E. Naredo and Vanghan, InternationalRice Germplasm Center, IRRI

The rare species O. schlechteri was

recently collected as living plants below

the Jamu Gorge in the Finisterre Moun-

tains of Papua New Guinea (PNG). This

small, stoloniferous wild relative of rice

is currently known to exist only in three

other locations: on the island of New

Guinea above the Jamu Gorge, Madang

Province, PNG; Baimuru, Kikori, Gulf

Province, PNG; and along the BeaufortRiver, Irian Jaya, Indonesia.

O. schlechteri is 2n = 4 = 48 (see

figure). Of the five other known species are tetraploid, and O. rufipogon and O. morphologically distinct from all other

from Papua New Guinea, O. officinalis are diploid. The systematic species in the genus Oryza, requires

longiglumis, O. minuta, and 0. ridleyi position ofO. schlechteri, which is furrher detailed study.

The somatic chromosome number ofRoot tip cell chromosomes of Oryza schlechteri.

GeneticsAnalysis of variance revealed that the good general combiners for ratooning

Combining ability of somerice genotypes for ratooning

in diallel mating systemS. Arumugachamy, P. Vivekarnuadan, and

M. Subramanian, Agricultural Botany De-

partment, Agricultural College and Research

Institute (ACRI), Madurai, Tamil Nadu, India

Six rice genotypes (Bhavani, MDU3,

IET6262, IET6709, IET7552, and

IET9239) and their 30 hybrids obtained

through complete diallel set were evalu-

ated for combining ability for the ratoon-

ing trait. Entries were raised in two 3-m

rows with 20- 10-cm spacing in a

randomized block design replicated threetimes during Oct 1988 at ACRI.

The crop was harvested at maturity,

cut at 20 cm aboveground. We evaluated

10 randomly selected parents and 5

hybrids from each replication. Ratoon-

ing ability was assessed as the number

of ratoon tillers generated from the

stubble.

variances due to general combining

ability (GCA). specific combining

ability (SCA), and reciprocal effects

(RE) were significant, which indicatedthe difference in ratooning ability

among genotypes (Table 1).

were highly significant for all parents:

from -1.64 (IET9239) to 1.45

(IET6709). The parents IET6709.

1ET6262, and IET7552 have positive

and significant GCA effects and are

Table 1. Analysis of variance for combining ability.

Source of DF Sum of Mean Ftable

The GCA effects for ratooning ability

variance squares square a (P = 0.01)

General 5 78.60 15.72** 3.29combiningability (GCA)

combining

ability (SCA)Reciprocal 15 33.33 2.22** 2.32

effect

GCA/SCAError 70 5.62 0.08

5.1:1

a** = significant at 1% level.

Specific 15 46.21 3.08** 2.32

ability (Table 2).

The nature of gene action in deter-

mining the inheritance of characters is

important in breeding programs. Thehigher GCA than SCA variance for

ratooning ability indicates the predomi-

nance of additive gene action in the

trait's inheritance. Hence improving

ratooning ability with parents IET6709,

IET6262, and IET7552 through the

pedigree method of breeding will be

effective.

Table 2. Estimate of general combining ability

effects for ratooning ability.

Parent GCA effectsa

Bhavani 0.24**

MDU3 0.90**

IET6262 0.76**

IET6709 1.45**

IET7552

IET92390.58**

1.64**

Var(gi) 0.01

LSD (P = 0.05) 0.15SE (gi) 0.08

a** = significant at 1% level.

IRRN 17:3 (June 1992) 5


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Some agrophysiological characteristics of BR11 and Laki under farmers' field conditions.

Character BK11 Laki t-test a

Grain yield (t/ha) 4.0 0.45 1.95 0.45 13.12**

Panicles (no./m 2 ) 207 28 127 28 8.75**

Filled grain (no./panicle) 102 19 74 11 5.72**

Sterile grain (%) 21.5 21.7

1.000-grain wt (g) 24 1 25 0.8

Harvest indexStraw yield (t/ha) 4.27 .70 7.97 2.3 6.36**

0.48 .04 0.20 0.04 22.49**

Sink:source (mg/cm2

) 37 28Leaf area (cm 2 /m2) 17.480 10.678 7.13**

Leaf area (cm 2/tiller) 113.5 19 111.5 17

Specific leaf weight 4.39 0.31 4.61 0.29 1.79ns

(mg/cm 2)

N content (%) 2.22 0.18 1.73 0.10

a Significant at 1% level (**). ns = nonsignificant.

We conducted a survey under farmers'

field conditions to identify the characters

that explain the difference in yield

potential between DWR and rainfed

lowland MVs.

Twenty 9-m2 plots for both the

traditional DWR variety Laki and the

rainfed lowland MV BR11 were selectedat random within a 5-km radius of BRRI,

Habiganj. Sampling was at flowering and

maturity stages. The climate at flowering

was similar for both varieties.

Laki yielded about 2 t grain/ha and

BR11, 4 t/ha (see table). Laki produced

10 t total biomass/ha and BR11, 8 t/ha.

The harvest index of Laki was less than

half that of BR11. Panicles/m2 and filled

grains/panicle were significantly lower in

Laki than in BR11. These characters limit

grain yield in Laki. Sink-source ratio was

also lower in Laki. The 1.000-grain

weight and sterility percentage were

similar in both varieties.The two varieties showed large

differences in leaf area/m2 and N content

of leaves. The smaller leaf area/m2 of

Laki was possibly due to its lower panicle

density. N content of Laki was below the

critical level; that of BR11 was above the

critical level for leaf photosynthesis in

Both photosynthetic capacity and

ability are limiting in Laki. These

observations indicate that both sink and

source prevent Laki from obtaining high

grain yield.

MVs.

Rice anther callus regeneration in 2 types of vessels.

Calli Plant

Vessel transferred to regeneration

regeneration efficiency

medium (no.) (%) d

Rea/M164

Petri dishes 210

Class jam jars 252

4.8 a

7.9 a

Rea/Cristallava HIPetri dishes

Glass jam jars 294

238 9.2 a

17.0 b

Lido/MiaraPetri dishes 748

Class jam jars 728

1.2 a

4.7 b

Total

Petri dishes 1196

Glass jam jars 1274

3.4 a

8.7 b

a Comparison of proportions with 2 at 1 df. Means followed

by a common letter are not significantly different at the 5%

level.

We studied the effect of type of vessel on

regeneration of anther-derived calli of

three F1 hybrids from temperate japonica

varieties.

The panicles were pretreated at 8-10C

for 7 d. The excised anthers were cultured

in the dark on N6 medium that was

solidified with 4.5 g agarose/liter, 2 mg (4-

chloro-2 methylphenoxy) acetic acid/liter

and 60 g sucrose/liter. After 4-6 wk, we

transferred the calli for regeneration to

either 90-mm-diameter disposable petri

dishes or to glass jam jars of the same

diameter and 0.5-liter capacity. Fourteen

calli were placed in each container on

10 ml of MS medium with 2 mg kinetin/

liter, 0.5 mg NAA/liter, and 40 g sucrose/

liter under high light intensity.

We noted more regenerated green

plants in jam jars for all the tested

genotypes. The ratio of albino to green

plants remained unchanged although the

number of albino plants increased.

The increase in air volume in the

vessel improves the regeneration rate (see

table) by acting as a thermal buffer that

limits the internal heating of the vessel's

atmosphere under high light intensity or

by permitting only a slow modification of

the atmosphere inside the jar.

Calli produce ethylene and carbon

dioxide. Their simultaneous presence at

high concentration is unfavorable to

organogenesis in rice. The concentration

of these gases builds slowly in larger

vessels.

Influence of type of vessel onregeneration of rice anther

calli

Breeding methods

B. Courtois, Institut de Recherches

Agronomiques Tropicales et des CulturesVivrieres/Centre International de Recherche

Agronomique pour de Developpement, Station

de Roujol, 97170 Petit-Bourg, Guadeloupe,

France

Yield potential

Agrophysiologicaldifferences betweendeepwater rice (DWR) andrainfed lowland modernvariety (MV) under farmers'field conditions

A. R. Gomosta, Bangladesh Rice Research

Institute (BRRI) Regional Station, Habiganj;

and K. A. Kabir, BRRI, Gazipur, Dhaka,

Bangladesh

Surveys of disease or insect incidence/

severity in one environment are useful

only if the information is related to other

variables (e.g., climatic factors, crop

intensification, cultivars, management

practices, etc.). By itself, information on

incidence in one environment does not

increase scientific knowledge.

6 IRRN 17:3 (June 1992)


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Grain quality Effect of land preparation methods on grain quality, 1988-90.a

Quality attributeComplete Partial Dry land

puddling puddling preparationRelation between rice grainquality and land preparation 1000-grain weight (g)

Total milled rice (%)

Head rice (%)methods

19.1 a

71.6 a

57.0 a

18.8 ab

71.1 a

56.2 b

70.0 b

54.7 c

18.2 b

Cooked grain length (mm) 12.4 a 12.2 a 11.8 a

A. Ali, M. A. Karim, L. Ali, S. S. A1i, M. Jamil, Bursting of cooked grains (%)6.0 c 7.2 b 9.7 a

G. Hassan, and A. Majid, Rice Research Amylose content (%) 29.3 a 3.7 a 29.5 a10.0 a 9.6 a 8.9 b

Institute, Kala Shah Kaku, Lahore, Punjab, Alkali spreading valuePakistan Gel consistency (mm)

6.8 a

54.0 a

6.0 a

50.0 a

6.9 a

43.0

Several methods of rice land preparation

are used in Pakistan depending on availa-

bility of irrigation water, soil type, and

ease of preparation.

We studied the effect of land prepara-

tion methods on grain quality by compar-

ing complete puddling (eight cultivation

and eight plankings under 30 d wet

conditions); partial puddling (four cultiva-

tions and four plankings under dry

conditions, and four cultivations and four

plankings under 10 d wet conditions); and

dry land preparation (eight cultivations

a Results were averaged for 1988-90. In a row, means followed by the same letter are not significantly different at the 5% level by

DMRT.

and three plankings under dry conditions grain length. protein content, and gel confollowed by flooding and transplanting). sistency, followed by partial puddling

We transplanted a medium-grain and dry land preparation methods (see

variety KS282 on the same day of 1988, table). The reverse trend was observed in

1989, and 1990. The experiment was laid bursting of cooked grains. The effect of

out in unreplicated 30- 60-m plots. land preparation method on amylose

Recommended crop management content and alkali spreading value was

practices were adopted. nonsignificant. The complete puddlin

Complete puddling produced the produced the highest quality grain

highest values for 1,000-grain weight. followed by partial puddling and dry land

total and head rice recoveries, cooked preparation methods.

Rice grain quality as Effect of split application of N fertilizer on grain quality, 1989 and 1990. a

influenced by splitapplication of nitrogenousfertilizer

Timing of N application

Quality characteristic

Basal and 30 DT Basal, 30, and 60 DT

A. Ali, M. A. Karim, G. Hassan, L. Ali, S. S.1,000-grain weight (g) 18.3 b

Total milling recovery (%) 70.2 a

Ali, and A. Majid, Rice Research Institute, Head rice recovery (%) 48.3 b

Kala Shah Kaku, Lahore, Punjab, Pakistan Cooked grain length (mm) 14.5 aBursting of cooked grains (%) 8.0 a

We studied the effect of split N applica-

tion on fine-grain strain 4048 during

1989 and 1990 dry seasons. Soil was

loamy clay, with pH 8.0, ECe 1.95 dS/m,

0.067% N, 10 ppm available P, and 65

ppm available K. The experiment was

laid out in a randomized complete block

design with three replications in a 4- 9-

m plot.

We applied a fertilizer dose of 100-50-

50 kg NPK/ha. P and K were broadcast

and incorporated into the soil during thelast puddling. N was applied in two splits

(half as basal, half 30 d after transplant-

ing [DT]), or in three splits (one-third

basal, at 30 DT, and at 60 DT).

Three splits of N fertilizer produced

significantly higher 1,000-grain weight

and head rice recovery, and less burst

grain during cooking than two splits (see

Proteinc ontent (%)

Amylose content (%)

Gel consistency (mm)

Alkali spreading value

8.7 a

24.8 a

61.0 b

4.2 b

19.0 a

70.7 a

53.7 a

15.1 a6.0 b

9.0 a

25.0 a

64.0 a

4.5 a

aResults are averaged for 1989 and 1990. In a row, means followed by the same letter are not significantly different at the 5% leve

by DMRT.

table). Values for gel consistency and the same quality groups: soft gel consis-alkali spreading were also significantly tency and intermediate gelatinization

higher for the three splits but remained in temperature.

Pest resistancediseasesA new symptom of tungro We tested four accessions ofOryzain rice glaberrima a West Africa cultivated rice

for resistance to tungro. The accessionsN. Kobayashi, R. Ikeda, D. A. Vanghan IRGC 100139, 100153, 102569, andIRRI; and S. Shigenaga, Kyoto University 103437 all showed severe systemic

necrosis, a new symptom of tungro

infection, 2 or 3 wk after inoculation

Japan

IRRN 17:3 (June 1992) 7

Protein content (%)


8/33

(WAI). This is distinct from the usual

tungro symptoms of stunting, yellow or

yellow-orange discoloration, and reduced

tillering observed in susceptible popula-

tions of other species.

Fifty 11-d-old seedlings of each

accession were inoculated with 10

viruliferous green leafhopper (GLH)

adults/seedling for 4 h. We caged another10 seedlings of each accession with 10

virus-free GLH adults/seedling for 4 h to

check whether necrosis resulted from

sucking damage by GLH alone.

ous GLH first showed necrosis at the

leaf tips 2 WAI. Necrosis advanced

systemically through the seedlings; few

survived beyond 3 WAI. Seedlings

caged with virus-

free GLH did not showany necrosis. Therefore, tungro viruses

Seedlings inoculated with virulifer-

caused the necrosis, which is the most

severe reaction to tungro we have

observed.

We have systematically been screening

wild relatives of rice for tungro resistance

and have also found systemic necrosis in

O. barthii, the close wild relative ofO.

glaherrima. This severe systemic necrosis

may be species specific.

Resistance to rice tungrobacilliform virus (RTBV)found in wild Oryza spp.

N. Kohayashi, R. Ikeda, and D. A.

Vaughan, IRRI; and S. Shigenaga, Kyoto

University, Japan

We evaluated wild relatives of rice to

seek new resistance genes for use inthe control of tungro. A partial core

collection of 156 accessions, represent-

ing the genetic diversity in the genus

Oryza, was used (Table 1).

Eleven-day-old seedlings were

inoculated with viruliferous green

leafhopper (GLH) adults at 10 insects/

plant for 4 h. Leaves were individually

sampled 2-3 wk after inoculation to

test for RTBW and rice tungro spheri-

cal virus (RTSV) infection by enzyme-

linked immunosorbent assay (ELISA).

Ten of the 12 accessions, whichwere not infected with RTBV, were

tested for antibiosis to GLH (Table 2).

Either a 10-d-old seedling or a leaf tip

of an adult plant from each accession

was placed in a test tube with five

GLH nymphs (2d instar). This was

replicated 10 times. We graded

antibiosis of each accession as high,

moderate, or low by counting the

surviving GLH nymphs each day for

3 d. The accessions resistant to any

virus were determined from the data of

more than 10 plants.In the O. sativa complex, O. nivara

and natural hybrids were resistant to

RTSV; but no accession in O. sativa

complex was resistant to RTBV infec-

tion.

The accessions, which were not

infected with RTBV, showed a low

infection rate with RTSV, except O.

8 IRRN 17:3 (June 1992)

longiglumis (IRGC 105146) (Table 2). The accessions resistant to RTRV

O. brachyantha (IRGC 100115), O. of- infection showed a high level of anti-

ficinalis (IRGC 105100, IRGC 105365), biosis to GLH. Thus it is difficult to dis-

and O. rhizomatis (IRGC 103421) were tinguish the resistance to virus infection

not infected by either RTBV or RTSV. from the resistance to the vector.

Table 1. Screening wild rices for tungro resistance.

Accessions (no.)

Species Genome Resistant toTested

RTBV+RTSV RTBV RTSV

O. brachyantha FF 5 1 0 4O. sativa complex

O. nivara AA 39 0 0 4

Natural hybrids AA 25 0 0 3

O. glaberrima AA 4 0 0 0

A. meridionalis AA 2 0 0 0

O. longiglumis Tetraploid 3 0 1 0O. ridleyi Tetraploid 5 0 2 0

O. officinalis CC 14 2 2 3

O. rhizomatis CC 6 1 0 00 2

O. malampuzhaensis BBCC 3 0 0 1O. minuta BRCC 12 0 0 5

O. rufipogon AA 6 0 0 0

O. barthii AA 6 0 0 0

O. ridleyi complex

O. offinicalis complex

O. eichingeri CC 5 0

O. punctata BB, BBCC 7 0 0 2

O. latifolia CCDD 5 0 1 1

O. grandiglumis CCDD 2 0 0 0O. alta CCDD 3 0 2 0

O. australiensis EE 4 0 0 2

Table 2. Reaction of RTBV-resistant wild rices to RTSV infection and antibiosis.

Species IRGC Originacc. no.

Plants Infectedtested with RTSV

(no.) (%)

Antibiosis

to GLHb

O. brachyantha 100115 Guinea 29 0 11

O. ridleyi 100821 Unknown 11 9 11

O. longiglumis 105146 Indonesia 24 33 11

O. officinalis 104672 Malaysia 20 5 H101453 Malaysia 30 3

105100 Brunei 28 0 H

105365 Thailand 41 0 H

105376 Thailand 29 3 M

O. latifolia 105139 Guatemala 25 4 H

O. alta 100967 Surinam 19 10 H

105685 Brazil 29 11 H

O. rhizomatis 103421 Sri Lanka 18 0

aH = high level of antibiosis, M = moderate level of antibiosis.


9/33

ance-even when varieties have insect

resistance. Resurgence of BPH popula-

tions on susceptible varieties due to the

destruction of natural enemies is well

documented. Little information is

available, however, on the impact of

these chemical sprays on BPH and

natural enemy populations on resistant

rice varieties.

We established a trial in a farmers

field in Caloocan, Koronadal, during the1986 wet season (Jul-Sep) to demonstrate

the effects of broad-spectrum chemical

applications on BPH and spiders (major

BPH predators) on resistant variety IR62.

An area of 800 m2 was planted and

divided into two equal parts. One part

was sprayed at 10 days after transplanting

(DT) with a synthetic pyrethroid

Wide hybridization between rice and officinalis have been successfully resistance reported are potential donors

most of its wild relatives is now possible. incorporated into advanced breeding for resistance to the tungro viruses.

Genes for insect resistance from O. lines. Therefore, the various sources of

Performance of a bacterialblight (BB)-resistant ricevariety in the endemicpockets of Konkan Region,India

V. S. Pande and A. M. Mandakhot, Konkan

Krishi Vidyapeeth (KKV), Dapoli District,

Ratnagiri, Maharashtra, India

Karjat 1 (Holamaldiga/lR36) is an early-

maturing rice with high resistance to BB

at both the vegetative phase and flower-

ing stage. The variety, released by KKV,

is specifically for the BB-endemic areas

of Konkan Region (west coast).

The variety and susceptible checks

EK70 (local) and Karjat 184 were tested

during the five kharif (monsoon)

seasons of 1985-86 to 1989-90, in

farmers fields. We recorded BB

incidence three times using the Standard

evaluation system for rice (SES) 0-9

scale.

At vegetative phase, Karjat 1 was

free of BB as foliar and kresek infec-

tions during all years studied (see table).

Average incidence of BB at flowering

and grain filling ranged from 0.12 to

1.24, with a maximum of 0.4 at flowering

stage and 1.5 at grain filling. Averageincidence of BB was 3.90-6.72 on

Karjat 184 and 3.92-7.22 on EK70.

infection of 3.54 and EK70, 3.64.

adopt Karjat 1 for cultivation in BB-

endemic areas of Konkan Region.

Karjat 184 had an average kresek

The study indicates that farmers can

Performance of Karjat 1, Karjat 184, and EK70 in BB endemic areas in Konkan Region, India, 1985-86 to 1989-90.

Av BB incidencea

Vegetativeb

Year Locations

(no.) Karjat 184 EK70 BB at flowering BB at grain filling Av grain yield (t/ha)

BB Kresek BB Kresek Karjat I Karjat 184 EK70

1986-87 50.0 0.1 1.4 2.4 0.4 2.4 6.2

7.7 7.0 5.0 4.4 0.1 6.2 5.2

4 5.0 2.4 5.0 3.0 0.1 7.2 7.0

2 2.4 2.0 3.2 2.4 0.0 4.6 4.9

6 4.4 6.2 5.0 6.0 0.0 5.6 5.6

1985-86 5

1987-88

1988-89

1989-90

Av 3.00 3.54 3.92 3.64 0.12 5.16 5.78

Karjat 1 Karjat 184 EK70 Karjat I Karjat 184 EK70

1.0 4.6 7.2 4.2 3.9 2.8

1.2 6.5 5.4 3.6 1.6 2.6

1.5 9.0 8.0 4.1 2.8 2.8

1.0 6.2 6.5 3.7 3.0 2.9

1.5 7.3 9.0 3.2 2.0 1.8

1.24 6.72 7.22 3.8 2.7 2.6

a1976 SES scale for BB: 0 = no BB incidcnce. 9 = 5 100% area of upper 3 leaves showing necrotic symptoms. SES scale for kresek: 0 = no incidence. 9 = 91-100% hills affected.

bKarjat I had

no BB at vegetative phase.

Pest resistanceinsectsInsecticide-inducedresurgence of brownplanthopper (BPH) on IR62

R. C. Joshi, Food and Agriculture Organiza-

tion (FAO), P.O. Box 1864, Manila, Philip-

pines; B. M. Shepard, Clemson University,

Coastal Research and Education Center, 2865

Savannah Highway, Charleston, SC 29414,

USA; P. E. Kenmore, FAO, P.O. Box 1864,

Manila, Philippines; and R. Lydia, IRRI

Outreach, Koronadal, South Cotabato,Philippines

Many farmers in Koronadal, Philippines,

apply sprays of synthetic pyrethroids to

their rice as early as 1-2 wk after trans-

planting (WT) regardless of numbers of

insect pests or beneficial arthropods.

These sprays are perceived as insur- Caloocan, South Cotabato, Philippines, 1986 wet season.Total number of BPH and spiders sampled by D-vac.

IRRN 17:3 (June 1992) 9


10/33

We evaluated Basmati rices comprising

19 scented dwarf, 6 scented tall, and 10

new entries or lines for resistance to stem

borer Scirpophaga incertulas (Lepidop-tera: Pyralidae) in the field during 1990.

Each entry was planted in 20-m2 plots at

20- 15-cm spacing with three replica-

tions. Total and affected panicles from 10

random hills in each plot were counted at

flowering stage to calculate damage.

Infestation (whiteheads) ranged from

6.3 to 51 % in the scented dwarfs (see

Screening Basmati rites for

stem borer resistance

K. S. Kushaha, L. R. Bharti, and D. V. S.

Punwar, Haryana Agricultural University,

Rice Research Station, Kaul (Kaithal).

Haryana, India

(decamethrin) at 8 g active ingredient/ha

as a foliar application using a knapsack

sprayer; the other part was untreated.

Weekly for 6 wk, 10 hills from each

plot were randomly sampled for BPH and

spiders using a D-Vac suction sampler.

Insects and spiders were identified,

counted, and their numbers plotted to

show population trends. Rice yields were

taken from each plot.

The BPH population in the sprayed

plot resurged to about 500 insects/20

Genetic sources ofresistance to whitebackedplanthopper in scentedquality rices

N. S. Rani, M. B. Kalode, J. S. Bentur,

D. Pati, and E. A. Siddiq, Directorate of Rice

Research (DRR), Rajendranagar, Hyderabad500030, India

Aromatic (Basmati) rices command a

premium price in international markets.

They have superfine grains, pleasant

aroma, and kernel elongation with soft

texture upon cooking. All of' the tradi-

tional Basmati types are tall, susceptible

to many insects and diseases, and low

yielding. It has been difficult to transfer

the key quality characteristics of Basmati

rices into productive dwarfs that have

pest and disease resistance.We screened 400 scented quality rices

to identify Basmati types with resistance

to whitebacked planthopper (WBPH)

Sogatella furcifera (Horvath), a major

pest in Basmati-growing areas in India,

brown planthopper (BPH)Nilaparvata

lugens (Stl), and gall midge (GM)

Orseolia oryzae (Wood Mason) under

artificial infestations in a glasshouse.

Some important quality traits, such as

aroma, kernel length (KL), length-to-

breadth ratio, anti kernel length after

cooking (KLAC), were also studied.None of the Basmati types were

resistant to either BPH or GM, but some

showed varied reaction to WBPH. HBC5

was the only variety found resistant to

WBPH (see table). HBC5 has extra-long

slender grains, KL of 7.42 mm, strong

scent, and a high KLAC of 13 mm.

Basmati Kota, with moderate resistance

10 IRRN 17:3 (June 1992)

hills; that in the unsprayed plot remained

below 100/20 hills (see figure). In

contrast, the number of spiders remained

low in sprayed plots but reached a peak

of more than 550/20 samples in the

unsprayed fields.

Rice grain yields were significantly

lower in the treated plot (137 kg) than in

the untreated one (159 kg). The larger

BPH number clearly reduced yields in the

sprayed plot, thus negating the possible

expression of insect resistance in IK62.

Any effects of a resistant rice variety

may be masked by unnecessary insecti-

cide sprays that induce BPH populations.

Early insecticide spraying kills spiders

and causes BPH numbers to multiply

unchecked. This increase of BPH puts the

varietal resistance of IR62 at risk because

it induces local BPH populations to more

quickly adapt to resistant varieties than

they would without the chemicaltreatment.

Key quality attributes of scented quality rices and reaction to WHPH. DKR, Hyderabad, India, l990 wet

season.

Nature of Kernel Length: Kernel length

Varietyresistancea

Score b Iength b breadth after coolingGraintype

Aroma d

(mm) (mm)

HBC5 R 2.7 7.42 4.21 13.0 LS SS

Dehradun Basmati MR 5.1 6.07 3.13 10.0 LS SS

Basmati 397 MU 4.4 6.67 3.83 13.7 LS SS

Basmati 405 MR 3.6 6.79 3.53 10.8 LS SSHBC85 MU 3.2 7.65 3.98 12.2 LS SS

HBC98 MU 3.6 6.63 3.83 13.7 LS SS

Basmati Kota MU 3.5 7.54 3.95 15.0 LS SS

Lua Nheden MR 4.4 5.74 2.94 8.5 LB MS

Basmati 370 S 9.0 6.63 3.45 12.5 LS SS

Mean 6.19 3.65 12.16CV (%) 11.9 18.3 20.0

a R = resistant, MR =moderately resistant. S = susceptible. b Scored by the by Standard evaluation system for rice scale of 0-9,1988.c LS = long slender, LB = long bold. dMS = mild scent, SS = strong scent.

to WBPH, has extra-long grains and KLAC. These varieties can be readily

showed the highest KLAC of 15.0 mm. utilized in breeding programs to develop

Basmati 397 and HBC98 also had high-yielding dwarf Basmati rices.

moderate WBPH resistance and good

Resistance of Basmati entries to stem borer.

Entry, culture Whiteheads(%)

HKR86 411BBC19 (check)Bas 370 (check)HKR403HKR239HKR86-40

HKR240HKR242HKR416HKR86-404HKR401IET120-11HKR236HKR410HKR238Pusa Basmati 1HKR228

Scented dwarf51.048.8

47.046.545.945.538.937.737.7

31.329.327.818.016.210.9

48.5

32.8

Kasturi 8.16.3

continuation on next page...

HKR243


11/33

9

5

5

5

Reaction of rice varieties to WBPH under green-

house conditions in 1991 wet season.

Variety Damage scorea

A21 3

IR50404-57-2-2-3 3

IR32843-92 5

IR49517-32 5

IR50404-47 5

OM746-I3 5

IR44595-70 5

IR44592-62 5

OM44-5 5

OM201 5

OM723-11E 5

IR64 5

OM723-7 5

OM723-11M 5

IR70 5

OM742-15 5

lR52280-117-1-1-3 5

IR42W-211-1-2-2-3

IR53970-100-3-3-2

A20A8 5

24A 5

Ptb 33 (resistant check) 3

TN1 (susceptible check)

a By the Standard evaluation system for rice.

Table continued

Entry, culture Whiteheads (%)

Scented tall

HBC19 43.9

HBC143 42.9

Pak Basmati 41.9

HBC46 38.3

Basmati 370 35.1

HBC28 32.1

New linesIET12606 50.8

IET12604 37.3

Basmati No. 2 25.3

IET12602 22.7

IET 12601 21.6

IET12607 19.3

IET12605 15.7

IET12608 12.0

IET12603 8.6

IET12609 6.7

Effects of whitebackedplanthopper (WBPH)Sogatella furcifera on ricevarieties in the greenhouse

Truong Thi Ngoc Chi, Entomology Depart-

ment, Cuulong Delta Rice Research Institute,

Omon, Haugiang, Vietnam

We screened 42 rice varieties and linesagainst WBPH using the seedling bulk

test. Test lines were sown 20 seeds/row

in 10-cm-long rows in 40- 30- 5-cm

iron seedboxes filled with 3 cm of fine

soil, in a randomized complete design

with three replications.

Seedlings were infested 7 d after

sowing with second- to third-instar

WBPH nymphs at 5 nymphs/seedling.

table). None of the scented tall entries Plant damage was assessed when all

were promising. plants of susceptible check TN1 had died.

and IET12608 showed promise for to WBPH with damage score 3, and 21

New entries IET12609, IET12603, Two lines showed moderate resistance

resistance to the pest. lines were moderately susceptible with

damage score 5 (see table).

Pest resistanceother pests

Assessment of riceresistance andsusceptibility to stemnematode Ditylenchusangustus

R. A. Plowright, J. R. Gill, and

T. E. Akehurst, International Institute of

Parasitology, 395a, Hatfield Road, St.

Atbans, Herts. AL4 OXU, United Kingdom

We examined ways to assess rice

resistance and susceptibility to stem

nematode D. angustus, the cause of

ufra. We screened selections, most of

which were identified through the

International Rice Ufra Screening Set

(1985-89), in successive glasshouse

trials against an isolate ofD. angustus

from Haugiang, Vietnam.

D. angustus nematodes and eggs was

placed in water 10-12 d after sowing

(10 cm deep) and confined close to

each seedling, using a 6-mm-diam

drinking straw. The straw was removed

per 7 d. Symptom development was

monitored daily and nematodes/plant

Inoculum consisting of 300

Diagrammatic representation of symptoms of D. angustus: A = susceptible, with severity rated 0-16. and B =

resistant.

were counted 28 d after inoculation

(DAI). This method was reliable,

giving 100% infection of the suscep-

tible check NC492 with 1,047D. angustus/plant (mean of 68 plants,

standard error of mean = 74).

Symptoms on the most recent leaf

were classified every 7 d as resistant

(incompatible) or susceptible (compat-

ible). Severity of susceptible responses

was scored on a scale of 0-16 (see fig.,

A). Some resistant seedlings exhibited

Proportion of plants of Rayada 16-06 showing

resistant and susceptible symptoms, 28 d after

inoculation withD. angustus.

D. angustus

Host response Plants

(%) Mean Range/

no./plant plant

Resistant-immune 13 0 0

Resistant-hypersensitive 49 2 0-13

Susceptible 38 46 6-572

IRRN 17:3 (June 1992) 11


12/33

a hypersensitive response that was visible

5 DAI. Resistance response was varied:

leaves showed discrete, small white

patches bordered by a yellowish halo,

sometimes over the entire leaf surface, or

the leaf midrib became yellowish, either

in discrete areas or along its length (see

fig., B). In what appears to be a strong

resistant response, a length of the

emerging leaf was completely chlorotic

below a green tip, with the leaf often

folding in the chlorotic region.

This response differs markedly from

the well-described susceptible reaction.

The necrosis of infected resistant tissue is

rapid, whereas it is slower in the suscep-

tible response and usually follows a

secondary infection by fungi.

The response was observed in some

seedlings of Bazail 65, CNL 319, Karkati

161, Rayada 16-02, Rayada 16-03, and

Rayada 16-06 to Rayada 16-09. We

screened 100 seedlings of Rayada 16-06

to examine interplant variation. We

observed host responses (see table).

Within a rice line, or between lines and

cultivars, the type of response and level

of susceptibility could be accurately

judged from visual symptoms. Numerica

scores of susceptible symptom severity a

28 DAI were linearly related to numbers

ofD. angustus/ plant (within Rayada 16-

06, correlation coefficient r= 0.70, P


13/33

Table 2. Yield of promising varieties in 5 farmers' fields (OFAT) in Cambodia, 1990. a

Yield (t/ha)Variety

Kok Bantey, Trapeang Veng, Trapeang Chan, Toul Koktrap, Mokda, RomeasRolear Phaer, Kampong Kampong Svay Rieng Hek, Svay Rieng

Chhnang

Don 0.5 0.3 1.2 1.4Khao Tah Petch 0.6 2.1 0.8 4.4 1.0

Tewada 0.5 1.6 0.7 4.5 1.0Local check 0.8 4.6 0.8 2.1 0.9

a Farmers' choice variety.

The floating rice area in Cambodia has

declined from 390,000 to about 110,000

ha. Reasons for the decline were the

policies of the ruling regime from 1974 to

1979, the security situation after 1979,

and the loss of floating varieties. An

urgent system of introducing varieties

and breeding lines and testing them in

multilocation trials was adopted in 1986.

Varieties Tewada, Khao Tah Petch,

and HTAFR77022-45-3-2-1 (Don) were

very promising in advanced yield trials

(AYT) and in on-farm adaptive trials

(OFAT) during 1989 and 1990 (Table 1).

In the OFATs, these varieties were given

to farmers in 1990 to test in their fields

under their own cultural practices, crop

management style, and constraints. Five

of the nine sets of OFAT were success-

fully completed. Farmers preferred thenew varieties over their old ones (Table

2) for reasons including better survival,

stable yield, desired maturity across

locations, and superior grain type. Seed

multiplication is under way.

Table 2. Resistance of ZH3 to B1 and BB. ZhejiangChina, 1989 and 1990. a

Score

EntryBI BB

1989ZH3 1Xiushui 48 (check) 3 5

3

1990ZH3 1 3

Xiushui 48 (check) 3 5

a By the Standard evaluation system for rice.

Table 1. Yield potential of ZH3 in China. 1989. a

Double-cropped Single-cropped

Site Yield Increase Yield Increase(t/ha) over (t/ha) over

check (%) check (%)

Hangzhou. 7.9 5.7* 9.1 10.5**Zhejiang

Zhenjiang, Jiangsu 6.8 3.1 8.8 2.2Wuhu, Anhui 6.7 2.9 8.0 8.7**

Xiaogan, Huban 6.9 4.2 8.7 5.8*ZH3 is a high-yielding japonica with

medium duration, resistance to blast

(BI) and lodging, wide adaptability, and

moderate resistance to bacterial blight

(BB). Since its release in 1990, ZH3

has been planted in double- and single-

cropped areas of South China.

ZH3 was selected from a cross

between medium line 84-35 (Torede 1

///Aijing 14/Keqing 3//Jinlei 440) and

Xiushui 04, a local popular modern

variety in Zhejiang Province. It yielded

6.7-7.9 t/ha in double-cropped areas and

8-9. 1 t/ha in single-cropped areas. These

yields exceeded those of local check

Varieties by 2.2-10.5% at four sites in

South China (Table 1).

Average growth duration of ZH3 was

134 d in double-cropped areas and 158 d

in single-cropped areas in Zhejiang. Its

gene for BI resistance comes from

Torede 1, Pi-z t (Table 2).

ZH3 is semidwarf (about 82.5 cm). It

has dense panicles that are about 15.2

cm long, 74.8 grains/panicle, 90.9%

seed fertility, and 1,000-grain weight of

26.5 g.

Bao Genliang, Crop Institute, Zhejiang

Academy of Agricultural Sciences,

Hangzhou 310021, China

ZH3, a high-yielding andmultide-resistance rice forsingle- or double-croppingin South China

Surveys of disease or insect incidence/

severity in one environment are useful

only if the information is related to other

variables (e.g., climatic factors, crop

intensification, cultivars, management

practices, etc.). By itself, information on

incidence in one environment does not

increase scientific knowledge.

a Significant at 5% (*) and 1% levels (**).

Irrigated germplasm improvementdeepwater

Three varieties of floatingrice released to farmers inCambodia

R. C. Chaudhary, IRRI - Phnom Penh.

Cambodia; D. W. Puckridge. IRRI - Bangkok,

Thailand; D. HilleRisLambers, IRRI-

Philippines; and M. Sarom, Agronomy

Department, Phnom, Penh, Cambodia

Table 1. Performance of promising varieties in advanced yield trials of floating rice in Cambodia, 1989 and

1990.

Av yield (t/ha) Agronomical character, 1990

Variety

1989a 1990 b Height Panicle length Flowering Duration Grains/ PAcpd

(cm) (cm) date (d) panicle (no.) score

Don 1.23 1.87 218 26 30 Nov 201 122 4.2

Khao Tah Petch 1.29 1.43 207 26 28 Nov 192 104

Tewada 1.00 1.67 201 25 25 Nov 195 1043.9

Local check 1.22 1.88 223 24 29 Nov 202 158 3.04.3

a Av over 4 locations. b Av over 6 locations. c Av over 7 locations. dPhenotypic acceptability.

Kampong Chhnang Chhnang

IRRN 17:3 (June 1992) 13


14/33

Upland rice is generally exposed to

severe weed infestation. Vegetative

vigor, large leaf area, plant height, and

N absorption at early growth stages are

related to the crop's ability to compete

with weeds.

We conducted trials during 1989

and 1990 aus (wet season) to screen for

suitable lines or varieties that can

compete with weeds.

The soil is silty clay loam, with pH

6.5-6.8. Test entries in 1989 were

BR4290-3-3-5, BR4290-3-1-10,

IR255-88-7-3-1, and varieties

Hashikalmi, BR20, and BR21. In 1990,

we discarded BR20 and IR255-88-7-3-

1 and used Kataktara as local check

because Hashikalmi was unavailable.

Test entries were grown under weed-

free conditions as one treatment.

The experiment was laid out in a

randomized complete block design

with three replications. Seeds were

sown on 3 May 1989 and 7 May 1990at 100 kg/ha in lines, 20 cm apart, in 3-

2.5-m plots.

Recommended fertilizer manage-

ment practices were followed, with an

additional 20 kg N/ha as urea applied

at 58 d after emergence (DE) to meet

the crop's demand. No insecticide was

used.

Weed and plant heights were meas-

ured at 0, 42, 72, and 88 d after seeding

(DAS). We recorded plant population

at 39 DE in 1989, but in 1990, only

140 plants/m2

were kept. In 1989,weeds were removed from 1 m 2,

cleaned, oven-dried at 70C for 72 h,

and weighed, but in 1990, weeds/m2

were counted. Leaf angle to the culm

was measured at dough stage.

Stress tolerance

Weed competitivenessupland rice cultivars in

of

Bangladesh

J. C. Biswas, S. A. Sattar, and M. K.

Bashar, Bangladesh Rice Research Insti-

iute, Joydebpur, Gazipur 1071, Bangladesh

Major weeds were Paspalum sp. and

Echinochloa colona. Minor weeds were

Cyperus iria, Cyperus rotundus,

Cynodon dactylon, Fimbristylis

miliacea, Acanthospermum sp., Eclipta

prostrata, and Commelina sp.

Under water stress, rice seedlings did

not emerge until 13 DAS in 1989; many

weeds emerged before this, indicating

their superiority in this condition. At 32

DE, rice entries were taller than the

weeds (Table 1). Weed weight was

lightest with Hashikalmi, possibly

because the taller plants intercept more

radiation (36.37%).

maturity. Although grain yield produc-

tion was not high under intense weed

pressure, yield of BR4290-3-1-10 and

BR21 was comparable to the local

check (Table 1).

Plant heights significantly differed at

In 1990, rice seedlings emerged at 5

DAS. Weed seedlings emerged in the

meantime, indicating a speed of germina

tion higher than that of rice. Plant height

leaf angles, grain yield, and growth

duration varied significantly because of

rice-weed competition (Table 2). Re-

duced leaf angles in all test entries may

be due to poor growth. The local check

and BR21 were more erect, which

allowed more light to penetrate. BR21

produced the highest grain yield in the

weeded plot, but produced only 0.22 t/h

in the unweeded. BR4290-3-1-10 yield

(0.51 t/ha) in the unweeded plot was

significantly higher than that of the

others. This line also performed well in

1989.

BR4290-3-1-10 is a promising line fo

uplands under weed stress but is inferior

to BR21 under weed-free conditions.

Table 1. Rice yield and some other parameters as affected by weeds, 1989 aus. a

Entry

Rice Height at 32 DE Plant Weed wt Radiation Grai

plant (cm) height at removed intercep-

(no./m2) maturity (g/m2) tion (%) (kg/h

Weed Rice (cm)

BR4290-3-3-5 176 26 a 35 a 71 b 215 b 27.10 374

BR4290-3-1-10 181 25 a 31 c 63 c 203 b 31.19 442 a

BR20 130 26 a 36 b 74 b 225 b 29.64 357

BR21 167 24 a 36 b 74 b 201 b 34.18 407 a

Hashikalmi (local check) 296 27 a 46 a 91 a 132 a 36.37 647 a

CV (%) 25.3 10.4 5.2 6.1 30.2 18.

Rice leaf angle ()

Grain yield Growth duration

BR4290-3-1-10 11 ab 13 a 25 bcd 32 abc 0.51 d 1.39 b 88 d 93

BR4290-3-3-5 11 ab 13 a 37 ab 41 a 0.25 e 1.09 c 96 a 97 a

BR21 9 b 11 ab 24 bcd 32 abc 0.22 e 1.89 a 93 bc 96 aKataktara 9 b 10 b 13 d 18 cd 0.22 e 1.04 c 95 ab 95 a

CV (%) 13.6 12.3 16.2 1.3

IR255-88-7-3-1 193 19 b 34 bc 57 d 200 b 28.01 359

a Separation of means in a column by DMRT at P 0.05 level.

Table 2. Some plant parameters as influenced by weed competition. 1990 aus. a

Entry Second leaf Flag (t/ha) (d)

Unweeded Weeded Unweeded Weeded Unweeded Weeded Unweeded Weede

a Separation of means across two columns weeded and unweeded by DMRT.

14 IRRN 17:3 (June 1992)


15/33

The experiment was laid out in a

randomized block design with four

replications. Urea, diammonium phos-

phate, and muriate of potash were

applied at 120 kg N, 27 kg P, and 24 kg

K/ha.We transplanted 45-d-old seedlings

of long-duration, short-statured rice

Crop growth rates and N uptake rates of transplanted IR64 rice as affected by Sesbania rostrata and

Aeschynomene afraspera GM or urea application. MRRTC. Muoz. Nueva Ecija, Philippines. 1988 dryseason.

N sourcea

S. rostrata

A. afraspera 0.7

Urea 1.4

LSD (0.05) 0.3

No fertilizcr N 1.9

aN rate: 90 kg/ha as GM basally applied, or as urea applied in 2/3-1/3 split.

Crop growth rates (g/m2 per d) N uptake rates (mg/m2 per d)

5-13 DT 13-20 DT 5-13 DT 13-20 DT

0.8 2.3

2.1

CROP AND RESOURCE MANAGEMENT

7.0

3.9

1.2

Physiolgy and plant

25 112

24 110

51 245

61 145

9 21

nutrition

Sesbania rostrata and

Aeschynomene afrasperaeffects on crop establishmentof transplanted lowland rice

K. H. Diekmann, S. K. De Datta, Agronomy,

IRRI; and J. C. G. Ottow, Justus-Liebig-

University Giessen, Federal Republic of

Germany

Anaerobic decomposition products in

flooded soils may affect root and shoot

growth of newly transplanted rice seed-

lings after organic matter amendment. We

evaluated the effects of S. rostrata and A.afraspera green manure (GM) amendment

on crop establishment of transplanted

lowland rice by conducting a field experi-

ment at the Maligaya Rice Research and

Training Center (MRRTC), Muoz, Nueva

Ecija, Philippines, during the 1988 dry

season.

5.9. Each kilogram of soil contains 14 g

organic C, 1.1 g total N, CEC 38 cmol c,

450 g clay, and 50 g sand. The field was

irrigated and kept flooded for 2 wk before

wetland preparation to allow the soil redoxpotential to reach equilibrium. The field

was plowed once (15- to 20-cm depth) and

harrowed twice. We broadcast and incor-

porated single superphosphate, KCl, and

zinc sulfate heptahydrate at 26-50-4.5 kg

P-K-Zn/ha before transplanting rice.

GM plants grown for 45 d outside the

trial area were harvested, transferred to the

experimental field, chopped into 5-cm-

long pieces, and incorporated by hand into

moist soil after the flooded plots were

drained 1 d before transplanting. GM was

basally incorporated at 90 kg N/ha using2.9 t dry matter/ha forS. rostrata (3.2% N,

C/N = 12) and 2.43 t/ha forA. afraspera

(3.7% N, C/N = 12). We compared these

GM treatments with urea N application at

the same rate and with a zero fertilizer N

control.

The experimental design was a random-

ized complete block with four replications.

The soil is a Vertic Tropaquept with pH

Twenty-one-day-old IR64 rice seedlings

were transplanted into water-saturated soil

at 3-4 plants/hill at 20- 20-cm spacing.

Plots were 29.4 m2. Floodwater depth was

kept at 5 cm after transplanting.

Six rice hills were sampled at 5 d after

transplanting (DT) and weekly thereafteruntil panicle initiation (PI) to determine

dry weight, N content, and N uptake. After

PI, four hills were sampled biweekly until

crop maturity.

Yellowing of plants and rice seedling

death were observed in the first 7 DT.

Missing hills were replaced. Plant damage

may have been due partly to transplanting

shock, but symptoms were more severe in

GM treatments.

Crop growth rates and N uptake rates

were significantly lower (P = 0.05) in GM

treatments than in urea and control treat-ments (see table). A. afraspera seemed to

damage rice seedlings more than S.

rostrata did, but this was not significantly

reflected in their crop growth rates.

Exchangeable NH4+-N levels at the

MRRTC site were high enough (data not

presented) to provide N for the rice

seedlings as proven by the higher crop

growth rate with zero fertilizer N than

with GM. Therefore, other factors must

have affected seedling vigor.

GM decomposition and the release of

organic acids, phenolic substances, and

other organic compounds probably

affected seedling root and shoot growth.

However, rice plants overcame the

additional stress caused by GM amend-

ment and gave the same N uptake at 34

DT and dry matter at 41 DT as did plants

fertilized with urea (data not presented).

In this experiment where missing rice

hills were replaced. grain yields in urea

and GM treatments did not significantly

differ (data not presented). But in farmersfields, where dead rice hills are not

replanted, farmers should delay trans-

planting by a few days after GM incorpo-

ration to avoid problems in establishing

the crop.

High concentrations of soil CO2 due to

Response to different Zncarriers of rice grown onUstifluvents in India

R. L. Bansol and V. K. Nayyar. Soils Depart-

ment, Punjab Agricultural University,

Ludhiana 141004, India

We studied the relative efficiency of Zn variety Jaya and applied three types of

carriers applied as foliar sprays for rice Zn in foliar sprays at two concentra-

on Ustifluvents. Soil was sandy loam tions each (see table). Plants were

with pH 8.4, EC 0.30 dS/m, 0.45% sprayed 4 wk after transplanting and

organic C, and 0.45 mg DTPA twice more at a 10-d interval. The crop

extractable Zn/kg soil. was grown to maturity and the yield

IRRN 17:3 (June 1992) 15


16/33

The N-use efficiency of prilled urea (P

in wetland rice is 20-50%. Rock phos-

phate-coated urea (RPCU), gypsum-

coated urea (GCU), and sulfur-coated

urea (SCU) are costly to produce: urea

supergranules (USG) are expensive to

apply. These costs reduce their econom

benefit although they supply N more

efficiently than PU. LGU is a new

Effect of foliar sprays of Zn on the yield and zinc

uptake by rice.

Zn source of Zn solution

Concentration Yield (t/ha) Zn

(%) Grain Straw (g/ha)

uptake

ZnSO47H2O 0.10 5.3 9.2 3010.20

Zn-EDTA5.8 10.8 394

0.01 5.4 9.4 2310.10 6.0 11.5 350

Zn-chelate 0.02 5.0 9.4 202(with phenolic 0.10 5.6 10.2 310

Controlgroup)

LSD (P = 0.05)4.3 7.4 1350.6 1.2 58

recorded. Grain and straw samples were

collected, processed, and analyzed for

Zn content.

Rice grain yield significantly in-

creased with foliar sprays of Zn, regard-

less of Zn source (see table). Higher Zn

concentrations increased grain yield, but

the effect was significant only for the

chelated form.

Zn-EDTA at 0. 1 % produced the

highest yield of 6 t grain/ha, which was

significantly superior to that with

ZnSO47H2O but at par with Zn-chelate

A similar pattern of yield response was

observed for rice straw. Zn uptake in ri

increased significantly the rates of all t

tested sources.

This study suggests that Zn applied

Zn-EDTA is more efficient at correctin

Zn deficiency in rice than either ZnSO4

or Zn-chelate.

Fertilizer management

Long-term effect of inorganicfertilizers, lime, and straw onlowland rice in Kerala

P. P. Joy, E. K. Syriac, P. K. C. Nair, P. J.

Ittyaverah, and C. A. Joseph Rice Research

Station, Moncompu, Thekkekara 688503, Kerala, India

We are conducting a study of the long-

term effects of continuous application of

N, P, K, lime, and straw incorporation on

lowland rice. This interim report covers

the first consecutive 4 yr from rabi (wet

season) 1987-88 to rabi 1990-91.

The field experiment has a permanent

layout of 40-m2 plots in randomized block

design with three replications and nine

treatments. The soil is a hydromorphic

silty clay with initial pH 4.8, EC 0.1 dS/m,

3.4% organic carbon (OC), 7 kg available

P/ha, and 100 kg available K/ha. Treat-

ments consist of combinations of 90-20-38

kg NPK/ha and lime, a control, straw

incorporation, and soil test recommenda-

tion (STR). STRs were 49-23-40-900 kg

NPK and lime/ha for the first 2 yr, 82-14-

35-1450 for the third yr, and 49-16-40-700

for the fourth yr.

Rice crop was harvested at about 10 cm

above ground level. For the straw incorpo-

ration treatment, straw was returned to the

respective plots after recording yield.

Lime was applied at first plowing, when

the straw was also incorporated.

Rice variety Pavizham (MO-6, 120 d)

was wet seeded at 100 kg/ha until 1989

kharif (monsoon); thereafter transplanting

at 15- 15-cm spacing was used. Fertiliz-

ers were applied as urea, mussoorie rock

phosphate, and muriate of potash as per

treatment; N and K in two equal splits as

16 IRRN 17:3 (June 1992)

inorganic

basal and at panicle initiation stage; and P

as fully basal. Weeds were controlled by

herbi-cides and/or hand weeding.

Pooled analyses of the data revealed

that the treatments, seasons, years, and

treatments seasons interactions were

statistically significant in grain yield.

Variations in grain yield was not signifi-

cant during kharif (see table). During rabi,

all the treatments that provided 90 kg

N/ha and STR were statistically on par and

produced significantly higher grain yields

than the treatments that received no N.

No interactions were statistically

significant for straw yield despite signifi-

cant treatment and seasonal and annual

Effect of inorganic fertilizers, lime, and straw on rice.

variations. Straw yield and growth and

attributes, such as plant height, panicles/

and panicle weight, varied significantly

with treatment and followed grain yield

trends, but had no significant interactio

Soil analyses data showed that treat-

ments produced no significant variation

pH, EC, OC, and available P and K in t

soil.

Results show that in the lowlands of

Kerala, rice responds to applied fertiliz

only during rabi. Among the three majo

nutrients, only N produced a significan

response. Straw incorporation and lime

application had no measurable effect on

yield. STR overpredicts the need for lim

and hence appears uneconomic.

Kerala, India, 1987-91.

(kg NPK/ha)

Treatment

Control

90-0-0

Straw alone

90-20-090-0-380-20-3890-20-3890-20-38

Grain yield (t/ha) Straw Plant Panicles Panicle Availab

Kharif Rabi Mean (t/ha) (cm)

yield height (no./m2) weight in the s

(g) (kg/h

2.0 2.4 2.3 2.5 71.8 269 1.96 12.4

2.0 2.5 2.3 2.4 72.2 295 1.89 15.2

2.2 3.0 2.6 3.1 78.3 315 2.32 9.6

2.2 3.4 2.8 3.3 77.3 309 2.24 8.8

2.4 3.1 2.7 3.2 78.0 303 2.27 9.2

2.0 2.4 2.2 2.4 73.5 270 2.18 8.8

2.2 2.7 2.5 3.4 76.7 316 2.35 10.8

1.9 3.1 2.5 3.1 78.9 313 2.27 9.2

+ 600 kg lime/haSoil test 2.1 3.1 2.6 3.4 77.3 317 2.37 8.0recommendation

LSDa (0.05) 0.6 0.5 0.5 4.6 35 0.28 ns

a LSD to compare treatments seasons interaction means.

Large granule urea (LGU), an

efficient and economic

source of N for wetland rice

I. Johnkutty and P. B. Mathew, AICARP-ECF

Unit, Kerala Agricultural University Man-

nuthy 680651 Thrissur, Kerala, India


17/33

material with a diam of 6-8 mm. It Effect of N source on grain yield. On-farm trials, Thrissur, Kerala, India, 1988 and 1989.

costs the same as PU to produce and

apply. Its size makes it ideal forGrain yield (t/ha)

Treat- N level

roadcast application.

We compared the performance of

LGU, RPCU, USG, and PU at eight

sites, each with four on-farm trials,

during the 1988 and 1989 kharif (Apr-

May to Sep-Oct) and rabi (Sep-Oct to

Dec-Jan) seasons. Soil texture varies

from clayey loam to loam, pH 5.1-5.4,

specific conductance 0.08-0.12 dS/m.

1.0-1.05% organic C, 5.0-6.5 kg

available P/ha, and 125- I70 kg

ment and source Kharif Rabi

no.a (kg n/ha)

1988 1989 Pooled 1988 1989 Pooled

1. Control (no N) 2.8 2.9 2.9 2.9 3.1 2.9

2. 84 - PU 3.4 3.6 3.5 3.6 3.2 3.4

3. 84 - USG 3.6 3.8 3.7 3.9 3.4 3.7

4. 84 - LGU 3.9 3.8 3.8 4.0 3.4 3.75. 84 - RPCU 3.6 3.8 3.7 3.8 3.7 3.8

6. 84 - LGU 3.9 3.9 3.9 3.9 3.5 3.7

7. 112 - PU 3.9 3.8 3.8 3.7 3.3 3.5

8. 112 - LGU 4.1 3.8 3.9 4.1 3.5 3.8

LSD (0.05) 0.1 0.2 0.3 0.1 0.3 0.3

available K/ha. All plots received 45 a 2 = 1/3 basal (B) + 1/3 at tillering (T) + 1/3 at panicle initiation (PI). 3 = full B: 4 = full B: 5 = full B:6 = 1/2 B + 1/2 T: 7

kg P and K/ha. P was applied basal. 1/3 B + 1/3 T + 1/3 PI: 8 = 1/2 B + 1/2 T: USG point placed at 5 cm depth, all other fertilizers were broadcast.

and K in two splits: half basal and half

at tillering. Jyothy was the test variety. equal the yield produced with 84 kg source of N. The nonsignificant differ-

Rice yielded more grain with N/ha as LGU, USG, or RPCU required ence between PU and LGU at 112 kg

modified urea materials than with PU 112 kg N/ha as PU. The extra yield N/ha may be due to Jyothys lack of

at the same N level (see table). To makes LGU an efficient and economic response above 84 kg N/ha.

Crop managementleaf once in 1988 trials and two times in

1989 trials.Effect of herbage cutting on treatments (control and cut) weredeepwater rice (DWR) in

acid sulfate soilarranged in a randomized complete block Average herbage yields, dry weight

design with 10 replications. Rice was dry basis, on acid sulfate soils ranged from

S. Taengsuwan, P. Charoendham, and T.

Kupkachanukul, Prachinburi Rice Research

Center, Prachinburi 25150, Thailand; and B, applied. Data on agronomic practices and 2). Nonacid sulfate soil areas in

S. Vergara, IRRI water depth are in Table 1. Prachinburi and Ayutthaya produced

Acid sulfate soil restricts rice growth, the collar level of the last fully developed matter accumulation might be the cause

seeded onto plowed soil at 120 kg seeds/ 0.4 t/ha from one cutting in 1988 to 0.6

ha. No fertilizer or other chemicals were t/ha from double cutting in 1989 (Table

In the cut plot, leaves were removed at more than 1 t/ha. Low rates of dry

resulting in low biomass production and

low grain yield. We assessed the effect

of herbage cutting on rice herbage and

grain yield in acid sulfate deepwater

areas during 1988 and 1989 wet seasons.

Four farmers fields-three with acid

soils, one without-planted to different

local DWR varieties were the experi-

ment sites. At each location, two

-

Table 1. Rice cultivars and agronomic practices in rice herbage experimental plots in acid sulfate deepwa

areas of Prachinburi, Thailand.

Acid

soil

Location Year sulfate Cultivar dale

Sowing Cutting date Maximum water Harvestin

First Second Depth (cm) Datedate

Bansang 1988 Yes Khao Lopburi 4 Apr 15 Aug - 70 15 Oct 19 DecBansang 1989 Yes Khao Lhong 7 Aug 10 Aug 10 Sep 125 10 Oct 22 DecKlongsong 1989 Yes Khao Lhong 7 Aug 10 Aug 10 Sep 120 10 Oct 25 DecMuang 1989 No HawnTawng 15 Apr 11 Aug 11 Sep 100 20 Sep 5 Dec

Table 2. Herbage yield, grain yield, and yield components of rice cultivars as affected by herbage cutting in acid sulfate deepwater areas of Prachinburi, Thailand

Herbage Grain yield Panicles/ Spikelets/ Fertility 1000-grain Dry matter HeightLocation Year Cultivar yield (t/ha) m2 panicle (%) wt (g) (t/ha)

(t/ha)

(cm)

Control Cut Control Cut Control Cut Control Cut Control Cut Control Cut Control Cut

Bansang 1988 Khao Lopburi 0.4 1.9 1.7 111 119 69 57 84 85 28.1 27.9 -

Bansang 1989 Khao Lhong 0.6145 126

1.6 1.5 105 107 98 93 81 80 26.0 25.9 9.4 7.9 255 230Klongsong 1989 Khao Lhong 0.5 2.0 1.8 87 91 93 89 89 88 25.9 26.0 10.6 9.1 245 235

Muang 1989 Hawn Tawng 1.1 2.2 2.1 120 125 98 89 79 81 26.7 27.0 15.0 13.7 255 242

Average 0.6 1.91 1.80 106 111 90 82 83 84 26.7 26.7 11.7 10.2 225 208

Differences in grain yield and yield components between control and cut plots were not statistically significant. Herbage removal significantly reduced dry matter and plant height,

IRRN 17:1 (June 1992) 17

-


18/33

of low herbage yields in acid sulfate areas. Plant height and dry matter production and increased cuttings may improve theHerbage cutting did not significantly were significantly decreased by relatively low herbage yield and make it

affect grain yield and yield components. herbage removal. Fertilizer application more economical.

Integrated pest managementdiseases

Growth and sclerotial

production of Sclerotiumoryzae on different media

Z. Ali, Plant Pathology Department, Institute

of Agriculture and Animal Science, Rampur,

Chitwan, Nepal

S. oryzae was grown on 15 natural and

synthetic media in petri plates to test their

growth and production of sclerotia.

Fungus colony diameters were measured

after 5 d of incubation. Petri plates were

further incubated to observe sclerotial

production. The plates were examinedevery 5 h to study sclerotial characters.

Average growth was maximum on

potato dextrose agar and minimum on

Backman and Kabana's medium and

Brown's agar (see table). All of the

media except Backman and Kabana's

medium and Neurospora V synthetic

medium produced sclerotia.

The results showed no correlation

among the radial growth of fungus, time

of initiation, color, size, arrangement, and

average number of sclerotia per plate.

Effect of different media on growth and sclerotial production ofS. oryzae.

Av colony Time until Arrangement of Color of Size of AvMedium diam a sclerotial sclerotia sclerotia sclerotiab sclerotia/

(mm) initiation (h) (m) plate (no.)

Backman and 26.7

Brown's agar 26.7 170 More toward periphery, Black 249.37 4875

Corn meal agar 50.7 120 More toward periphery, Black 266 13455

Czapek-Dox agar 63.3 125 Equally scattered Brownish 248.90 17550

Dextrose marmite 46.7 170 Equally scattered Shiny 266 1346.5

Neurospora V synthetic 35.7

Nutrient glucose agar 51.3 125 Equally scattered Black 274.86 4075

Oatmeal agar 65 145 More toward periphery, Black 248.26 17225.5

Peptone sucrose agar 51.3 130 More toward periphery, Black 248.30 41471.5

Potato carrot agar 46.7 120 Equally scattered Shiny black 274.86 45882Potato dextrose agar 73.3 120 Equally scattered Shiny black 274.86 45882Radish root extract agar 30 145 Equally scattered Brownish 268 23075

Rice polish agar 41.3 125 Equally scattered Black 294.30 12490.5Richard's agar 36.7 130 More toward periphery, Black 248.90 21650

Sach's agar 35 125 Equally scattered Black 230 12255.5

aAfter 5 d, based on 3 replications.

bAv of 100 sclerotia.

cLSD value of average colony diam (mm) at 5% = 3.98. CV = 5.27.

Kabana's medium

less toward center

less toward center

black

agar black

medium

less toward center

less toward center

black

less toward center

Effect of humic acid (HA) onseverity of rice blast (BI)

R. Thangaveli and R. Ramabadran, Plant

Pathology Department, Faculty of Agricul-

ture, Annamalai University, Tamil Nadu,

India

We studied the effectiveness of graded

levels of HA extracted from lignite on

the severity of BI in rice varieties IR50(highly susceptible) and IR20 (moder-

ately resistant) under greenhouse condi-

tions.

HA powder at the rate of 0, 10, 20,

30, and 40 kg/ha was dissolved in the

required quantity of 0.01 N KOH to

obtain pH 7.2. These solutions were

then mixed thoroughly into pots that

18 IRRN 17:3 (June 1992)

Effect of humic acid level on B1 incidence.a

IR50 IR20

HA level Mean Angular Decrease Mean Angular Decrease

(kg/ha) disease transformed from control disease transformed from control

incidence (%) value (%) incidence (%) value (%)

0 51.3 45.7 27.8 31.8

10 25.2 30.1 33.5 15.5 23.2 27.3

20 22.3 28.2 38.3 13.3 21.3 33.0

30 36.5 37.2 18.7 19.7 26.4 17.2

40 40.9 39.8 13.1 22.4 28.2 11.3

aMean of 3 rcplications.

already had the recommended dose of Disease incidence was assessed using a

fertilizer. Seedlings were transplanted; score chart of 0-9.

treatments were replicated three times. HA application reduced B1 severity.

artificially inoculated with the B1 ha.

pathogen Pyricularia oryzae Cav.

At 50 d after sowing the plants were Reduction was maximum with 20 kg/

- - - - -

- - - - -

- -


19/33

Comparative transmission ofthree tungro isolates bygreen leafhopper (GLH)

G. Dahal, I. Dasgupta, G. Lee, and R. Hull,

John lnnes Centre for Plant Science Research,

Colney Lane, Norwish NR4 7UH, United

Kingdom

We studied the transmission of three

tungro isolates obtained from the Philip-

pines, Malaysia, and India by a Philippine

GLH population. Adult GLHs fed for 3 d

on plants of rice cultivar TN1 infected

with rice tungro bacilliform virus (RTBV)

and rice tungro spherical virus (RTSV) of

the isolates. The GLHs then fed for 1 d on

nearly 2-wk-old seedlings of 12 rice

cultivars using mass inoculation at about 4

insects/seedling.

In another experiment, we determined

the reaction of these cultivars to RTBVusing agroinoculation. Test plants were

injected, 15-20 d after sowing, at the base

of their stems with 50 l of a viscous

suspension of Agrobacterium tumefaciens

A4 (pRTRB 1162) using a Hamilton

microsyringe.

About 4.5 d after inoculation, we

compared the test plants with the uninocu-

lated control plants to determine reduction

in plant height, leaf discoloration, and

RTBV and RTSV infection, which was

monitored by enzyme-linked immuno-

sorbent assay. The relative concentrationsof RTBV-DNA in agroinfected plants was

determined by nucleic acid hybridization

method using 32P-labeled full-length

cloned RTBV DNA (pJIIS2).

RTSV either singly or together varied

between the isolates. The Indian isolate

produced higher proportions of doubly

infected plants on cultivar TKM6 than did

the other isolates. The Malaysian isolate

produced more doubly infected plants on

cultivars ASD7, Utri Merah, Utri Rajapan,

Balimau Putih, and TKM6 than did thePhilippine isolate. The Malaysian isolate

also produced more severe yellow-orange

leaf discoloration on cultivar ASD7 than

did the Indian isolate, which was more

severe than the Philippine isolate. Agroin-

fected RTBV plants of cultivars ASD7

and Ptb 18 produced the most severe

yellow-orange discoloration.

The transmission profiles of RTBV and

Reaction of 12 rice cultivars to RTRV and relative concentration of RTRV-DNA in agroinoculated plants.

Reaction a to Reaction to RTBV RTBV-DNA

by agroinoculation d concentration in plants

(% infection) relative to that in TN1 eCultivar

GLHb Tungroc

ASD7 R

Ptb 18 R

ARC 11554 R

Gampoi 30-12-15 R

Pankhari 203 MR

Utri Merah S

Utri Rajapan SBnlimau Putih S

Vikrmnarya f

FK135 S

TKM6 S

TN1 S

I

I

R

R

R

R

RR

R

S

S

S

S

S

S

S

S

I

SI

S

S

S

S

High

High

Low

Intermidiate

Low

Low

LowLow

High

N/A

a IRRI data. b Based on seedling damage rating (IRRI). c Based on percentage infection in mass inoculation in cages.dI (intermidiate) = 31-60%. S. (susceptible) = more than 61 %. e Low = less than 20%. intermidiate = 20-40%. high

= more than 41 %, - = not determined, N/A = not available. fDr. A. Gosh. Hyderabad. India, pers. comm.

Results showed that most of the

cultivars that appeared resistant by

leafhopper inoculation were apparently

susceptible by agroinoculation (see table).

Except for two GLH-susceptible cultivars,

Utri Merah and Balimau Putih, plants

infected with RTBV by agroinoculation

fell into the susceptible category. The

relative concentration of RTBV-DNA in

Utri Merah, Balimau Putih, Utri Rajapan,

ARC11554 was low, while that in TN1,

ASD7, Ptb 18, and TKM6 was high.

Our results provide additional evi-

dence that Utri Merah, Utri Rajapan,

Balimau Putih, ARC 11554, and Gampai

30-12-15 show some resistance to RTBV

when inoculated by GLH. But on agroin-

oculation, only Utri Merah and Balimau

Putih show any resistance. Thus, agroin-

oculation is a promising technique for

determining true resistance in rice while

avoiding the effect of leafhopper

resistance.

Dependence of incubationperiod and symptoms of ricetungro disease (RTD) oninfection stage in ricefields

N. S. Astika, N. Suwela and G. N. Aryawan,

Food Crop Protection Center VII, P.O. Box 88

Denpasar, Bali; and Y. Suzuki, Directorate of

Crop Prorection, P.O. Box 7236/JKSPM,

Jakarta 12072, Indonesia

For both field epidemiological studies and

management of RTD, it is essential to

estimate when and how many hills were

infected. Diagnosis based on visible

symptoms is often the most practical

method to quickly survey fields. To

improve visual diagnosis, we studied howincubation period and duration of RTD

symptoms are affected by infection stage.

Experiments were laid out in a field at

Celuk Field Laboratory, Bali, late 1989 in

the dry season when RTD occurrence was

negligible. Variety Krueng Aceh was

transplanted 21 d after sowing. For

inoculation in the field, one outer stem of

a hill was inserted in a glass tube, sup-

ported by an erect stick. ANephotettix

virescens adult was released in it for 1 d

after 1 d of access to RTD-diseased hills.

Inoculation 1 d before transplanting (DBT)was made in test tubes. We observed plants

daily for 5 wk. We graded symptoms and

confirmed diagnosis by enzyme-linked im-

munosorbent assay test.

The incubation period was positively

correlated with the infection stage except at

1 DBT (see table). The infection at 1 DBT

showed inconspicuous, pale-yellow

discoloration, and prolonged duration of

incubation, Gr. 1, and Gr. 2. Plants infected

at 1-5 wk after transplanting (WT) devel-

oped the typical leaf-yellowing symptoms.

Duration of Gr. 3 for those infected at 1-3WT lasted less than 2 wk. Stunted leaves

remained the only visible symptom after

the yellow ones dropped off.

in the same hill, it became difficult to

detect infection unless symptom records

were available. In contrast, leaf yellowing

at 5 WT lasted until 10 WT when the

As healthy plants covered infected ones

IRRN 17:3 (June 1992) 19

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20/33

We conducted a trial in a farmer's field in

Banglane, Central Thailand, during 1990

wet season to determine the effects of

foliar sprays on BPH. Plots of 12 15 m

were laid out in a randomized complete block design and direct seeded using

susceptible variety Suphan 60. Nine

insecticide treatments were applied at 20

35, 45, and 60 d after sowing (DAS)

using 500 liters water/ha with a motor-

T. Bhudhasamai, P. Silapasorn, and

C. Shoiwtip, Rice Entomology Research

Group, Entomology and Zoology Division

Department of Agriculture, Bangkok 10900,

Thailand

Effect of foliar spray

insecticides on brownplanthopper (BPH)

resurgence in rice

We sampled modern rice varieties

(MVs) BR153, Jaya, and BW293-2 and

traditional varieties (TVs) Atti,

Dhursray, and Mashino bhog for rice

thrip damage during Aug 1989 in 11

fields in Gaylephug, Bhutan. Crop age

was 26-60 d after transplanting (DT).

We recorded damaged leaves from three

replications of 20 randomly selected

hills per field.

Seven fields in four villages were

sampled for damage by defoliators. Ricevarieties were the same except for

BW2Y3-2. Crop age was 45-60 DT.

Thrip damage was 7.2-26.9% in the

MVs and 1.5-4.7% in the TVs (Table

1). Defoliator damage was 0.8-6.6% in

the MVs and 0.4-5.8% in the TVs(Table 2).

The MV selections appear to be

more susceptible to thrips than TVs in

southern Bhutan. Defoliators, however,

showed no distinct preference.

Damage by rice thrips anddefoliators in southernBhutan

RTD symptom development in plants infected at different stages in the field. Bali, Indonesia, 1989 dryseason.

Stage Plants Plants Mean durationd(d)

at tested infected

inoculation (no.) (no.) Incubation b Gr. 1-Gr. 2 Gr. 2 - Gr. 3 Gr. 3 - Gr. 4 Gr. 4 - Gr. 5

1 DBT 28 14 11.28 b 1.14 c 9.71 d 7.85 a 2.92 a1 WT 27 13 8.92 a 0.00 a 3.30 bc 7.38 a 14.91 c2 WT 27 16 9.18 a 0.25 ab 2.93 b 13.37 b

27 8 11.12 b 0.37 b 1.50 a 13.37 b 6.87 b6.12 b

5 WT 27 11 14.54 c 0.27 ab 4.72 c7 WT 27 8 18.37 d 1.62 d -

3 WT

a In a column means followed by the same letter are not significant different at the 5% level by DMRT. b Incubation = from

all discolored leaves dry but stillattached; Gr. 5, leaves stunted but not yellow or dry.infection to Gr. 1.; Gr. 1, 50% of a leaf discolored; Gr. 4,

observation was terminated. Plants

infected at 7 WT did not develop Gr. 3

symptoms. Distinct changes in leaf color

did not occur, but panicle development

was affected in plants infected at 9 WT.

symptoms different from those in the

laboratory. Many of the hills infected at

early stages are overlooked if leaf

yellowing is the basis for diagnosis. We

confirmed that this holds for many

susceptible varieties, such as IR36 and

IR64.

RTD-infected plants in fields develop

Integrated pest managementinsects

G. S. Arida, C. Dorji, and K. L. Heong, IRRI

Table 2. Damage to rice leaves by defoliators a in

Gaylephug, Bhutan, August 1989.

Crop Damaged

(DT) (% SE)

Location Variety age leaves

Bhur Farm Modern 47 6.4 0.84

Bhur Farm Modern 47 6.6 1.0

Bhur Farm Traditional 47 5.8 0.6

Panpani Modern 45 0.8 0.2

Patabari Modern 60 5.4 0.5Patabari Traditional 60 1.2 0.60

Surey Traditional 60 0.4 0.1

aRice leafflolders Morasmia and Cnaphalocrocis, case worm

Nymphula, and an unidetifilied larva

aDamaged leaves (%) =

damage leaves

tota1 leavesx 100

Table 1. Damage to rice leaves due to feeding of

Haplothrips sp. Gaylephug, Bhutan, August 1989.

Crop Damaged

Location Variety agea leaves b

(DT) (% SE)

Lodrai

Lodrai

international rice research newsletter vol.17 no.3

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