Antagonistic Activities of Trichoderma harzianum Against Pythium aphanidermatum and Pythium myriotylum on Tobacco

Trichoderma harzianum rendered Pythium aphanidermatum and P. myriotylum non‐viable in Petri dish dual culture. The Pythium mycelia from such cultures showed natural autofluorescence in the regions of interactions, indicating their death. Non‐volatile and volatile fungicidal activities were detected in T. harzianum culture. Lytic activity of β‐(l,3)‐glucanase was detected on the cell walls of the Pythium spp. There was a significant decrease in the disease incidence when T. harzianum was incorporated into sterile soil, whereas the effect was insignificant in natural soil.