Studies on sheath blight of rice (Oryza sativa L.) caused by Rhizoctonia solani Kuhn
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Date
2014
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Publisher
CCSHAU
Abstract
Sheath blight of rice caused by Rhizoctonia solani Kuhn is one of the major fungal disease of
rice in tropical Asia causing upto 50% loss in grain yield. In Haryana, sheath blight considered to be a
minor disease upto 2005, has attained the status of a major disease on all types of rice varieties viz.
scented, non-scented, inbreds and hybrids. The present study was undertaken to assess the losses due to
sheath blight in popular scented and non-scented rice varieties, to study the effect of weather
parameters on disease development as well as to identify rice genotypes showing slow blighting against
sheath blight. Sheath blight was recorded in all the major rice growing districts both on scented and
non-scented high yielding varieties and hybrids in varying intensity. In non-scented high yielding
varieties, maximum disease severity of 40-45 per cent was recorded in varieties HKR 47, PR 113 and
PR 114. Among hybrids, the disease severity (35-45%) was more in hybrid PA 6129 and Swift as
compared to other hybrids. Among scented varieties, maximum disease severity was (25-45%)
recorded in Pusa Basmati 1121 followed by Pusa Basmati 1. The present investigations have revealed
that the losses in grain yield were differed significantly with scented and non-scented cultivars.
However, there was no significant reduction in grain yield in the plots inoculated at 60 (stem
elongation) and 75 days after transplanting (booting). The vertical disease spread ranged between 38.43
to 49.78 per cent in Basmati CSR 30 while there was 11.11and 4.04 per cent reduction in grain yield of
paddy with a vertical disease spread of 51.54 and 37.05 per cent in HKR 127. Role of weather
parameter in the progression and development of the sheath blight of rice revealed that a Tmax range
between 310C to 330C, Tmin range between 160C to 250C and relative humidity (morning and evening)
more than 90 per cent played major role in the progression of the disease. The regression equation
developed indicated that Tmin played major role in the development of the sheath blight of rice. The
delayed transplanting resulted in lesser disease severity in Basmati CSR 30 while the reverse trend was
observed in HKR 127. Out of fifty scented and non-scented rice genotypes evaluated, five genotypes
viz. N-22 (Acc. 6264), N-22 (Acc. 4819), HKR 05-476, Tetep and N-22 (Acc. 19379) exhibited slow
blighting components against sheath blight as the disease progression was significantly reduced. The
apparent infection rate and area under disease progress curve was considerably lower in these
genotypes. Moreover, in most of these genotypes, the incubation period was delayed and there was no
sclerotia formation till maturity of the plants.
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Keywords
Rhizoctonia solani, Sheath blight, Yield losses, Weather parameter, Slow blighting