Abstract: Sclerotium rolfsii
is a polyphagus soil inhabitant and ubiquitous facultative saprophyte. This pathogen is known to cause disease in more than 500 crops. Studies of variability within the population in a geographical region are important because these also document the changes occurring in the population. Hence different pathogenic isolates of S. rolfsii
obtained from different regions and crops of southern Karnataka. The morphological studies on the pathogen showed variation among different isolates. The colony diameter of all the isolates varied from 4.10 to 8.00 cm after 72 h of incubation, sclerotial number per plate ranged from 261.7 to 1048.7. However, the sclerotial colour ranged from light to dark brown, and their size varied from 1.10 to 2.10 mm with spherical to round shape. The test weight of sclerotial bodies ranged between 40.40 to 71.00 mg. Among the liquid media, ragi flour broth showed maximum dry mycelial weight (352.00 mg) whereas, sclerotial production was more in malt extract broth (247.70).