Ecologic and taxonomic studies on Pythium as pathogenic soil fungi

I. Vertical distributions of several pathogenic soil fungi in soil

Abstract

Comparisons were made among three pathogenic soil fungi. Pythium aphanidermatum, Rhizoctonia solani (an isolate from broad bean seedling) and Sclerotium rolfsii, concerning their vertical distributions in soil.
Mycelial density at each depth in soil was measured by contact slide method, and the pathogenicities of the fungi inoculated at different soil depths were determined by the use of indicator plants.
R. solani maintained a high mycelial density even at the depth of 10-15cm, P. aphanidermatum at 5-10cm, while S. rolfsii only at the surface layer.
When inocula were buried at different depths in soil, the pathogenicity of each fungus was the highest at 5-10cm with R. solani, at 2.5-10cm with P. aphanidermatum, while at the only surface with S. rolfsii.
There was better mycelial growth toward the upper and lower layers with both R. solani and P. apanidermatum than that with S. rolfsii.