Chlamydospore formation by Trichoderma spp. in natural substrates

Abstract

Various isolates of Trichoderma spp. formed chlamydospores in oat kernels placed in sterile and natural soils and in excised tissues of corn and bean inoculated with a conidial suspension. In an axenic oat-loam soil system, T. viride, T. harzianum and T. hamatum produced 1-38 .times. 107 chlamydospores/g of oat tissue. The soil type and its organic matter content did not affect the number of chlamydospores formed. In oat kernels retrieved from natural soils infected with Trichoderma conidia, .apprx. 10% were chlamydospores of indigenous Trichoderma spp. that infested and colonized the oats. Another 10% were attributed to the isolates added to soils as conidia. The remaining chlamydospores belonged to Fusarium spp., unidentified fungi or were nongerminable on the media used. In excised corn and bean tissues infested with Trichoderma, from 19-61 .times. 106 chlamydospores/g of tissue were formed by the phyllosphere fungi; 10% of the chlamydospores were from the introduced isolates and the remainder from indigenous Trichoderma spp., Fusarium spp., and unidentified fungi. The results suggest the probable importance of Trichoderma chlamydospores in the survival of this genus in soil.