<scp> <i>Trichoderma koningiopsis</i> </scp> ‐assembled synthetic <scp>PGPR</scp> community manage <scp> <i>Fusarium</i> </scp> damping‐off and promote growth of <scp> <i>Pinus massoniana</i> </scp> seedlings

Abstract BACKGROUND Fusarium oxysporum causes damping‐off disease in Pinus massoniana seedlings. While Trichoderma koningiopsis can enhance seedling resistance by regulating rhizosphere plant growth‐promoting rhizobacteria (PGPR), the specific bacterial compositions and their role in disease resistance remained undefined. To elucidate this mechanism, we used amplicon and metagenomic sequencing to identify T. koningiopsis ‐assembled PGPR. Synthetic PGPR communities were constructed from isolated strains to validate their effects on disease suppression and growth promotion. RESULTS Microbial community analysis indicated that T. koningiopsis reshaped the bacterial community: Actinospica , Dyella , and Streptomyces decreased in presence, and Bacillus and Arthrobacter increased. A total of 153 PGPR strains were isolated from the T. koningiopsis ‐inoculated treatment. Of these, eight strains demonstrated significant inhibitory effects against F. oxysporum , ranging from 33.81% to 59.52%. Four synthetic communities (SynComs) (C1, C2, HT, and 2K) were further constructed, exhibiting superior inhibitory effects against F. oxysporum compared to individual strains. Compared to the control, the C2 and HT SynComs increased seedling height by 10.18% and 9.44%, and reduced disease incidence by 50% and 36.67%, respectively. These treatments also enhanced protective enzyme activity and alleviated membrane damage. At the molecular level, the C2 and HT SynComs boost plant resistance by modulating the plant hormone and mitogen‐activated protein kinase (MAPK) signaling pathways, thereby activating the expression of crucial resistance genes such as PR1, FLS2, and CAT1. CONCLUSION Trichoderma koningiopsis alters the composition of rhizosphere PGPR community. The synthetic PGPR community assembled under the influence of T. koningiopsis effectively enhances damping‐off resistance and promotes the growth of Masson pine seedlings. © 2026 Society of Chemical Industry.