Variability Studies in Isolates of Sheath Blight of Rice Caused by Rhizoctonia solani Kuhn

Sheath blight is caused by Rhizoctonia solani which is known as a destructive disease and a major bottleneck for rice production in India as well as world. Eleven isolates of sheath blight pathogen were collected from major rice growing states such as Karnataka, Tamil Nadu, Kerala, Andhra Pradesh, Telangana, Odisha. Rhizoctonia solani is known to show high variability in terms of morphological, cultural and sclerotial characters. Hence study was conducted at Research and Development, Rallis India Limited, Bangalore to know the variability between the isolates which were collected from various locations. Studies on cultural variability revealed that colony colour varied from whitish brown to pale brown with slow, moderate and abundant growth patterns. Among the eleven isolates, majority were fast growing followed by medium growth. Size of sclerotia ranged from minimum of 1.00mm (Rs-9) to maximum of 1.97mm (Rs-8). Maximum isolates had excellent number of sclerotia (>60) produced per petridish. 3-4 days were required for initiation of sclerotia formation for all the isolates. Based on pattern of sclerotia formation, isolates produced sclerotia in central ring, scattered, central & scattered and central & peripheral manner. Sclerotia is formed either in aerial or surface mycelium or on both aerial and surface mycelium. Colour of sclerotia ranged from light brown to dark brown with rough texture.