Epidemiology and Management of Rice Sheath Rot in Jammu Region

Abstract

newline During the survey of five districts of Jammu division (Jammu, Samba, Kathua, Rajouri and Udhampur), the overall range of the per cent disease index ranged between 15.83-38.71 and 15.67-37.00 per cent during cropping seasons Kharif 2019 and 2020, respectively. Based on the pooled data of 2019 and 2020, it was observed that, temperature (max. and min.), relative humidity (evening) and rainfall showed significant and negative correlation. However, relative humidity (morning), showed significantly positive correlation with disease severity. On the basis of pathogenicity test, all the test isolates (31) were categorized into three groups viz., highly, moderately and less virulent. Isolates of Sarocladium oryzae were further categorized into different groups on the basis of colony characteristics (radial growth, colony colour, pattern of growth and topography). The length and breadth of conidia ranged between 4.62-7.90 and#956;m and 1.05-2.64 µm respectively, whereas the hyphal width ranged between 1.28-1.91 and#956;m in all the test isolates. Among six nutrient media, Oat Meal Agar supported significantly higher colony growth of 80.65 mm after 12 days of inoculation. The incubation period of ten S. oryzae isolates varied from 2.57-3.45 days. Mean maximum lesion size across the genotypes has developed by SO1 (192.72 mm2) after 8 days of inoculation and it proved as the most virulent isolate. The molecular analysis using sixteen ISSR primers revealed a remarkably high level of genetic polymorphism in selected twenty four isolates of S. oryzae. Significant positive correlation (r) was observed between disease severity and per cent loss in 1000 grain weight among rice genotypes investigated during both the cropping seasons. One hundred forty five rice genotypes were screened against sheath rot under artificially inoculated conditions and it was observed that nine genotypes viz., TMRH-2110, UPLRH-179510, RRX-805, Rasi, K39, K 448, Basmati 123, Pusa 44 and SJR 5 were showed resistant response to the disease. Among bio-contr