Variability of Pathogens Associated in Causing Root Rot/wilt of Soybean in Northern Karnataka

Soybean [Glycine max (L.) Merill.] is a protein rich oilseed crop. It is considered as a golden bean, miracle bean and wonder crop of the 20th century because of its characters and usage. In India, losses due to various diseases are estimated as 12 per cent of total production. The ischolar_main trot/ wilt complex has become a major production constraint in Karnataka. Three pathogens are involved in causing ischolar_main rot/wilt namely, Sclerotium rolfsii, Rhizoctonia bataticola and Fusarium sp.The association of these pathogens involving two or three varied from region to region. On the basis of morphological characters, the pathogens were identified as Sclerotium rolfsii. which produces the mustard sized sclerotial bodies, Rhizoctonia bataticola which produced brown to black, right angle branched mycelia with septa and Fusarium sp. which produced three kinds of spores viz., microconidia, macroconodia and chlamydospores. The results of physiological and morphological variations are discussed in this paper.