Genetic diversity and virulence spectrum of Rhizoctonia solani, the incitant of banded leaf and sheath blight of maize

Banded leaf and sheath blight (BLSB) of maize caused by Rhizoctonia solani is one of the most important yield‐limiting factors faced by growers in India. The pathogen is known to be highly diverse, and several species are known to cause BLSB. In the current study, forty‐four isolates of R. solani associated with maize were collected from different agro‐ecological zones of Punjab, a north Indian state. These were characterized genetically and phenotypically and for their virulence behaviour. Using internal transcribed spacer (ITS)‐based species‐specific markers, we confirmed the association of two species viz., solani (100%) and oryzae‐sativae (18.18%) with BLSB with later being detected in mixed infection. All the isolates belonged to anastomosis group AG1‐IA with a typical amplicon size of 265 bp. Genetic variation in the associated Rhizoctonia sp. was analysed using 27 inter simple sequence repeats (ISSR) markers which revealed high degree of polymorphism (PIC value ranging from 0.819 to 0.921) and clustered the Rhizoctonia population into two major groups. Based on fungal morphology, the hierarchical cluster analysis placed 44 Rhizoctonia isolates into six major groups (M1–M6). The virulence of each isolate studied on four hybrids and seven inbred maize lines revealed that maize hybrid JH3459 and inbred LMDR‐2 were less susceptible to Punjab population of Rhizoctonia species. Partial correlation was also obtained between genetic diversity, pathological variation and geographical origins of isolates. This is the first attempt to study the diversity of Rhizoctonia sp. associated with banded leaf and sheath blight of maize in Punjab state.