Abstract
<jats:p>Chlamydospores are stress-resistant propagules that improve the stability and shelf life of Trichoderma-based biocontrol products, but the genetic basis of their production remains poorly understood. Previous transcriptomic analyses of Trichoderma virens GV29-8 identified the hypothetical gene TRIVIDRAFT_211280 as a candidate regulator of chlamydospore development. To investigate its role, researchers generated a gene deletion mutant using CRISPR/Cas9-mediated homologous recombination and constructed a complemented strain. The wild-type, mutant, and complemented strains were compared for growth, morphology, biomass production, conidiation, and chlamydospore formation under both nutrient-rich and chlamydospore-inducing conditions. Deletion of TRIVIDRAFT_211280 had no effect on colony morphology, radial growth, biomass accumulation in inducing medium, or the timing and progression of chlamydospore development, indicating that the gene is not essential for chlamydospore morphogenesis. However, under nutrient-rich conditions, the mutant exhibited significantly greater biomass accumulation (11.8% increase) and conidial production (34.1% increase) than the wild type. Chlamydospore yield was also higher in the mutant at day 6, although overall differences across time points were not significant. These findings suggest that TRIVIDRAFT_211280 functions as a condition-dependent negative regulator of biomass and propagule production and may represent a target for improving spore yields in Trichoderma biocontrol formulations.</jats:p>