Trichoderma-Bioenriched Vermicompost Induces Defense Response and Promotes Plant Growth in Thai Rice Variety “Chor Khing”

Vermicompost (VC) produced by African nightcrawler earthworms (<i>Eudrilus eugeniae</i>) is a natural fertilizer with a rich microbial community. <i>Trichoderma asperelloides</i> PSU-P1 is an effective antagonistic microorganism with multifaceted activity mechanisms. This research aimed to develop <i>Trichoderma</i>-bioenriched vermicompost (TBVC) to promote plant growth and induce the defense response in the Thai rice variety "Chor Khing". <i>T. asperelloides</i> PSU-P1 was tested against <i>Rhizoctonia solani</i>, the pathogen of sheath blight disease, using a dual-culture assay. The results showed that <i>T. asperelloides</i> PSU-P1 effectively inhibited <i>R. solani</i> in vitro growth by 70.48%. The TBVC was prepared by adding a conidial suspension (10⁸ conidia/mL) to vermicompost. The viability of <i>Trichoderma</i> persisted in the vermicompost for 6 months and ranged from 1.2 to 2.8 × 10⁷ CFU/mL. Vermicompost water extracts significantly enhanced seed germination, root length, and shoot length compared to a control group (<i>p</i> < 0.05). Plants that received the TBVC displayed significantly longer shoot and root lengths and higher total chlorophyll content than control plants (<i>p</i> < 0.05). The TBVC induced defense response by increasing the enzyme activity of peroxidase (POD) and polyphenol oxidase (PPO) in comparison with control plants. Rice grown in the TBVC had a significantly reduced incidence of sheath blight caused by <i>R. solani</i> in comparison with control rice (<i>p</i> < 0.05). Furthermore, the fungal community of rice plants was analyzed via the high-throughput next-generation sequencing of the internal transcribed spacer (ITS). The fungal community in the TBVC had greater alpha diversity than the community in the VC. Phylum Ascomycota was dominant in both samples, and a heat map showed that <i>Trichoderma</i> was more prevalent in the TBVC than in the VC. Our results indicate that the enrichment of VC with <i>Trichoderma</i> increases growth, enhances the defense response, and reduces the incidence of sheath blight disease in the Thai rice variety "Chor Khing".