Assessment of morpho-cultural, genetic and pathological diversity of Rhizoctonia solani isolates obtained from different host plants

Rhizoctonia solani is a destructive soil borne plant pathogen that infects various crops including rice. A total of 35 isolates of R. solani from rice and other different hosts were collected and established. Morphological characterization was done on PDA media by analyzing radial growth, sclerotial pattern and colony colour. Pathogenicity test was conducted in a susceptible variety of rice Pusa Basmati 1. Maximum lesion height (86%) was observed for isolate TP3 and TP26 whereas, the minimum disease was observed for the isolate TP30 (29.2%). Molecular markers namely, internal transcribed spacer (ITS), universal rice primer (URP) and simple sequence repeats (SSR) were used to determine the genetic diversity of the pathogen. The phylogenetic tree obtained based on ITS region sequences grouped R. solani isolates in a single main cluster and 6 subclusters. Based on URP and SSR markers, isolates of R. solani were grouped into three and six clusters respectively. The structure analysis and AMOVA analysis revealed greater genetic variation within populations (91%) compared to among populations (9%). The results demonstrated that R. solani isolates evaluated were pathogenic to rice, irrespective of the host, however, variation exists at molecular level. The findings highlighted the diversity and complexity of the genetic background of R. solani which will be helpful to develop management strategies against the sheath blight disease of rice. Further, R. solani isolates from the host species finger millet ( Eleusine coracana ), lablab bean ( Lablab purpureus), and ginger ( Zingiber officinale ) were first time characterized from the North-Eastern state through this study.