Diversity of Rhizoctonia solani associated with pulse crops in different agro-ecological regions of India

Four hundred seventy Rhizoctonia solani isolates from different leguminous hosts originating from 16 agro-ecological regions of India covering 21 states and 72 districts were collected. The disease incidence caused by R. solani varied from 6.8 to 22.2 % in the areas surveyed. Deccan plateau and central highlands, hot sub-humid ecoregion followed by northern plain and central highlands and hot semi-arid ecoregion showed the highest disease incidence. R. solani isolates were highly variable in growth diameter, number, size and pattern of sclerotia formation as well as hyphal width. The isolates obtained from aerial part of the infected plants showing web blight symptoms produced sclerotia of 1–2 mm in size whereas, the isolates obtained from infected root of the plants showing wet root rot symptoms produced microsclerotia (<1 mm). Majority of R. solani isolates showed <8 μm hyphal diameter. Based on morphological characters the isolates were categorized into 49 groups. Seven anastomosis groups (AGs) were identified among the populations of R. solani associated with the pulse crops. The frequency (25.6 %) of AG3 was the highest followed by AG2–3 (20.9 %) and AG5 (17.4 %). The cropping sequence of rice/sorghum/wheat-chickpea/mungbean/urdbean/cowpea/ricebean influenced the dominance of AG1 (16.3 %). Phylogenetic analysis utilizing ITS-5.8S rDNA gene sequences indicated high level of genetic similarity among isolates representing different AGs, crops and regions. ITS groups did not correspond to the morphological characters. The sequence data from this article has been deposited with NCBI data libraries with JF701707 to JF701795 accession numbers.