Evaluation of vertical and horizontal spread of sheath blight in rice varieties for resistance against Rhizoctonia solani

Sheath blight caused by Rhizoctonia solani Kuhn is one of the important diseases of rice, resulting in heavy yield loss in rice every year. The present study was undertaken to determine the degree of vertical and horizontal spread of sheath blight in six rice cultivars viz. Swarna, Pusa Basmati 1, Pusa 1121, Tetep, Vikramarya and Pankaj when inoculated with Kapurthala (RS-1), New Delhi (RS-2) and Moga (RS-3) isolates in open field pot experiments. On inoculation with isolate RS-1 and isolate RS-2 cultivar Swarna was found to be most susceptible with maximum relative lesion height (RLH) and cultivar Tetep the most resistant. Pusa Basmati 1 and Pusa 1121 were either susceptible or moderately susceptible. Vikramarya and Pankaj were either resistant or moderately resistant. Isolate RS-1 was found to be the most virulent producing 47.8%, 39.1%,33%, 13.6%, 14%, and 20.4% RLH in cultivars Swarna, Pusa Basmati1, Pusa1121, Tetep, Vikramarya and Pankaj respectively followed by isolate RS2 producing 36.6%, 33.2%, 26.9%, 6.5%, 12.8% and 14.8% RLH on cultivars Pusa Basmati1, Swarna, Pusa1121, Tetep, Vikramarya and Pankaj respectively. The incubation period for the three isolates ranged from four to seven days. Isolate RS-1 was found to be the most virulent whereas isolate RS-3 was least virulent among the three isolates. Horizontal spread was also maximum with isolate RS-1 followed by isolate RS-2 and isolate RS-3.