Survival Dynamics of Trichoderma longibrachiatum Tr58 in Conidia- and Chlamydospore-Amended Soils with Different Moisture Levels

Two types of Trichoderma longibrachiatum Tr58 propagules, conidia and chlamydospores, were added to soils with different moisture levels. The survival dynamics of Tr58 in soils were determined. There are positive linear relationships between soil moisture levels and germination rates of the two propagules. In natural non-sterilized soil, the germination of more than 95% conidia and 60% chlamydospores was inhibited, while a high soil moisture content and sterilization were beneficial to spore germination. The inhibitory effect of soil with 80% moisture content on the germination of chlamydospores was almost completely eliminated after sterilization. Twelve months after the conidia inoculated to the natural soil, the Tr58 propagules decreased continuously, which was hastened in soils with lower moisture content and almost near zero 24 months later, in all soils. In chlamydospore-amended soils, the Tr58 propagules generally showed a dynamic process of decreasing in the first month, increasing in the 2nd month, and then decreasing gradually. The average Tr58 content in chlamydospore-amended soils with 5, 10, 20, 40, and 80% moisture content was 19.2 times that of conidia-amended soils at 12 months. At 24 months, the Tr58 content was about 2.2% of the initial Tr58 content and 114 times that of conidia in soils with 20% moisture content. However, for 80% moisture content, the Tr58 content in soil was 0.0038% of the initial content of Tr58. According to the results of this study, 10–20% soil moisture content was the most favorable for the long-term survival of Tr58, and the survival ability of chlamydospores was stronger than that of conidia and had greater application potential in disease control.