Abstract

Banded leaf and sheath blight incited by Rhizoctonia solani f. sp. sasakii Khunn. (Teleomorph: Thanatephorus cucumeris) is gaining devastating potentials in India. The pathogen is reported to show variation in expression of symptoms on the same genotypes grown in different locations. Fifteen isolates from trans-gangetic plains of India were collected to examine the cultural and morphological variability and pathogenic behaviour on host Zea mays. The isolates were from maize and rice host origins. Considerable variability was found among the isolates. The isolates of maize origin were poor sclerotia producing in culture, formed compact dense/fluffy, pale white to yellowish growth on PDA, producing irregular to organized, smooth surfaced sclerotia, faster radial growth in culture, acute branching of hyphae and high pathogenicity. The rice isolates showed a contrasting behaviour in forming sub-central to scattered, pitted sclerotia lighter in weight than maize counterparts, compact sparse colony, slow to medium radial growth, light brown to dark brown colony. Aerial bearing was not recorded in most of these isolates. All the rice isolates were fast sclerotia initiating in culture; however, higher incubation period was recorded in pathogenicity tests. The lesions were also scattered and disease score ranged from 2.6–3.1. The cultural and morphological parameters used in this investigation may be used to examine the biology of R. solani isolates from other agro-climatic regions also.