Seedlings of winter rye collected from yellowing patches during October to November 1985—1987 showed oospores of Pythium species in apparently healthy as well as in discolored roots. Examination of 1550 root pieces of rye on CMA yielded fungi belonging to 35 genera. The most commonly isolated ones were Fusarium spp, Penicillium spp, Mucor spp, Mortierella spp. and Cladosporium spp. Pythium spp. were isolated from 35 root pieces on CMA. Identified species were P. splendens, P. irregulare, P.

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... imile, a species resembling P. aristosporum and a species resembling P. ultimum. In in vitro and in vivo, tests on the cereals winter rye, spring wheat, oats and barley the pathogenicity of some Pythium isolates varied from high (P. splendens, P. irregulare) to moderate (P. irregulare, P. dissimile) and low (a species resembling P. ultimum).