Survival and Proliferation of Propagules ofTrichodermaspp. andGliocladium virensin Soil and in Plant Rhizospheres

Abstract

Laboratory-grown conidia of Trichoderma spp. and G. virens were sensitive to soil fungistasis. Germination laboratory-grown conidia in natural soil varied from 1 to 22%, depending on the species used. In contrast, chlamydospores from a liquid fermentation system or from potato-dextrose broth germinated readily in soil (39-99%). Trichoderma spp. and G. virens grew vertically downward through soil (< 2.0 cm) and the numbers of propagules increased 100-fold (from .apprx. 104 to 106) when either of the 2 genera was added in fermentor biomass containing traces of a food base and consisting mostly of chlamydospores. No significant increases occurred when conidia without a food base were added to soil. Trichoderma spp. were isolated from the rhizosphere of potato plants 4 and 8 wk following seed piece treatment with fermentor biomass of both fungi. Populations of both Trichoderma spp. and G. virens increased in soil planted with cotton to which fermentor biomass was added. However, the rhizosphere and nonrhizosphere populations were not significantly different which indicates that the food base was one of the factors responsible for the increase.