Morphological and pathological variability of Rhizoctonia solani isolates from dhaincha-potato crop rotation and their mycelial compatibility relationship

Rhizoctonia solani (teleomorph: Thanatephorus cucumeris ) is a ubiquitous plant pathogen infects various agricultural and horticultural crops. In this investigation, isolates of R. solani were collected from collar-rot infected dhaincha plants and black scurf affected potato tubers from potato based crop rotation to determine their morphological variability, mycelial compatibility and cross-infectivity. Significant variations in cultural and morphological features were observed among and between the R. solani isolates from both the hosts. Dhaincha isolates grew faster than those potato isolates and hyphal width of both host isolates varied from 6.24 to 11.70 μm. Considerable variability was observed in sclerotial characteristics viz . sclerotia colour, size, intensity, and distribution pattern. Most of the dhaincha isolates produced macro (> 1.26 mm) size sclerotia while potato isolates formed micro (≤ 1.25 mm) size sclerotia. Hyphal interaction studies showed that all isolates from potato belonged to AG-3 and dhaincha isolates belonged to AG1-IA group. Mycelial compatibility studies revealed that 76.67% of pairing was compatible while 23.33% of pairing exhibited non-compatible interaction. Cross-infectivity test revealed that R. solani potato isolates did not infect dhaincha plants whereas dhaincha isolates showed the varied degree of pathogenicity on potato and Rhizoctonia -like atypical symptoms were observed on the tuber surface. In this study, we report the first time of R. solani AG composition infecting potato in dhaincha-potato rotation in India. The outcomes of this study will be helpful for developing management strategies and breeding programs on varietal evaluation for effective control of Rhizoctonia diseases of potatoes.