Improved selective medium for isolating Cylindrocladium crotalariae microsclerotia from naturally infested soils.

Reduced development of fusaria and other undesired fungi, and improved recognition of Cylindrocladium crotalariae colonies on soil-dilution plates were accomplished by supplementing a previously used medium (sucrose-TBZ medium) with three quaternary ammonium compounds, replacing peptone with tyrosine, and increasing the concentration of sucrose to yield a water potential of - 10 bars. These changes eliminated the need to treat soil with NaClO to control undesired fungi. The new medium, designated sucrose-QT medium, allowed increased recovery of C. crotalariae microsclerotia from all 16 naturally infested soils tested.