Population structure of Rhizoctonia solani inciting sheath blight of rice in Haryana, India

Rhizoctonia solani Kuhn inciting sheath blight is known to cause substantial quantitative and qualitative losses in rice. Sixty six isolates of R. solani representing different agro-ecological regions of Haryana were classified based on their cultural and morphological, pathogenic and genetic traits. R. solani isolates were found highly variable both in mycelial and sclerotial characters. The mean vertical disease spread caused by R. solani isolates on five rice cultivars viz. Tetep, IR 64, Pusa Basmati 1, Govind and HKR 127 varied between 24.67 and 57.25% and the fungal isolates formed three clusters based on their pathogenic behaviour. Inter simple sequence repeats (ISSR) and Universal rice primers (URPs) were used to study the population structure of R. solani isolates. The Nei’s diversity (h), Shannon’s diversity index (I) and percentage of polymorphic loci (P%) were observed to be 0.2761, 0.4301 and 100%, respectively at the population level. Genetic variation was maintained within the populations as reflected by the higher gene flow (Nm = 4.5997). Agro-ecological regions contributed to 6% of the total genetic variation, whereas the major proportion of genetic variation (89%) was attributed to the differences within populations and only 5% among populations. © 2021, Indian Phytopathological Society.