BIOLOGY AND MANAGEMENT OF FALSE SMUT OF RICE [Oryza sativa L.) CAUSED BY Claviceps oryzae - sativae Hashioka IN KARNATAKA
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Date
1999-08-30
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UNIVERSITY OF AGRICULTURAL SCIENCES GKVK BANGALORE
Abstract
Systematic studies were carried out on false smut of
rice with respect to its survival, perpetuation, cultural studies,
life cycle and to develop integrated management strategies.
Disease incidence was maximum (23.78%) in Udupi district. Crop
sown beyond July 10th suffered least (0%). Weather parameters
like lower maximum temperature (<31 °C), minimum temperature
(19°C) and higher relative humidity (>90%) during 50 per cent
flowering were favourable for the disease development.
False smut has significantly reduced the per cent seed
germination (25.26%) and 1000 grain weight (48.06%) and
increased the chaffiness (40.86%). Healthy seedlings recorded
high amount of phenol and ortho-dihydroxy phenol than the
seedlings emerged from infected panicles. Chlamydospores
germinated by producing one to four conidia in a wide pH
range of 4.5 to 8.5. Production of true sclerotia was observed
for the first time in Karnataka. True sclerotia germinated on
autoclaved moist sand in 30 days at a temperature of 27 + 2°C
by producing two to six stromatic heads. Fungus was identified as Claviceps oryzae-sativae and showed maximum
radial growth in rice yeast dextrose agar. Chlamydospores and
Pseudosclerotia retained their viability upto four and seven
months respectively under room temperature. Sclerotia and
chlamydospores were the source of survival and perpetuation
of the fungus and helped in the disease initiation and disease
cycle. Among different methods of inoculation evaluated,
spraying of chlamydospore suspension on the inflorescence
during flowering was the best method. Carbendazim (0.1%) was
the most effective fungicide both under laboratory and field
condition. Eucalyptus citriodora leaf extract was effective in
inhibiting chlamydospore germination. Out of 80 genotypes
screened, Kavya, lESH 1, IR 30864 were free from infection both
under natural and artificial condition.
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