Phenotypic and Genomic Characterization of Trichoderma citrinoviride JS84: High-Temperature Growth, Antagonistic Activity, and Beneficial Effects on Tomato

High temperature can limit the effectiveness of fungal biocontrol agents. In this study, we investigated the growth, antagonistic activity, and plant-beneficial effects of Trichoderma citrinoviride JS84 and characterized its genome. Multilocus phylogenetic analysis supported its identification as T. citrinoviride. JS84 maintained vigorous mycelial growth at 40 °C during a 36-h assay and exhibited antagonistic activity against Fusarium oxysporum and Botrytis cinerea at 35 °C. Microscopy revealed attachment and coiling of JS84 hyphae around B. cinerea hyphae. JS84 promoted tomato growth most effectively at 1 × 106 conidia mL−1 under hydroponic conditions, with growth promotion also observed in soil-grown plants. JS84 pretreatment reduced the relative abundance of a B. cinerea target sequence by 53.9% and decreased pathogen-associated cell death. Following pathogen challenge, changes in phytohormone levels and defense-related gene expression were consistent with a priming-like response. Genome annotation identified 11,755 predicted protein-coding genes, 450 carbohydrate-active enzymes, and 46 putative secondary-metabolite biosynthetic gene clusters. These results support further evaluation of JS84 as a biocontrol agent for tomato.