<i>Trichoderma koningiopsis</i> Induced Changes in Root Exudates of Masson Pine Seedlings Alter Rhizosphere Microbiome to Enhance Damping‐Off Disease Resistance

Damping-off disease, primarily caused by Fusarium oxysporum, poses a significant challenge to the cultivation of Masson pine (Pinus massoniana) seedlings. Although Trichoderma koningiopsis improves damping-off disease resistance in Masson pine by regulating the rhizosphere microbial community, the underlying mechanisms remain unknown. Metabolomic analysis showed that T. koningiopsis altered Masson pine root exudates, especially plant organic acids such as capric acid (CA), lauric acid (LA) and pelargonic acid (PA). Co-culturing rhizosphere microbes with 0.1 mM CA, LA, PA and a combination of the three (1:1:1, CDNs1) significantly inhibited F. oxysporum and promoted the growth of rhizosphere biocontrol strains (Trichoderma, Penicillium and Bacillus), with CDNs1 exerting a superior effect. Amplicon sequencing and RT-qPCR showed that CDNs1 significantly altered the microbial community composition in the rhizosphere, especially inhibited the growth of Fusarium and enriched beneficial microbes (Trichoderma and Penicillium). CDNs1 effectively decreased the incidence and severity index of damping-off disease in Masson pine seedlings by 73.33% and 41.67%, respectively. Mechanistically, CDNs1 enhanced resistance to damping-off disease by modulating plant hormones, oxidative stress defences and the photosynthesis pathway. Collectively, this study provides insight into the mechanism by which T. koningiopsis enhances damping-off disease resistance by regulating the rhizosphere microbial community.