Objective To develop an efficient Trichoderma-based biocontrol agent for managing blister rust in Pinus armandii Franch.

Methods In this study, seven endophytic Trichoderma strains (T1~T7) isolated from P. armandii Franch. were evaluated for their mycoparasitic ability against Cronartium ribicola aeciospores. Assessments were conducted through mycoparasitism experiments, scanning electron microscopy observations, enzyme activity assays, and pot seedling control experiments.

Results All tested Trichoderma strains were capable of colonizing aeciospores, although their abilities varied. Strain T1 and T2 exhibited strong mycoparasitic abilities, significantly disrupting the cell walls of aeciospores and causing spore ruptured and cytoplasmic leakage. The aeciospores wall significantly induced the chitinase and β-1,3-glucanase activities of Trichoderma strains, with T1 and T2 showing the highest enzyme activities under induced conditions. Co-culture experiments of different Trichoderma strains of synthetic microbial communities (SynCome) demonstrated that the SynCome of T1, T2, and T4 significantly enhanced cell wall-degrading enzyme activities（0.512、0.386 U·mL^-1）, thereby increasing the mycoparasitism rate and showing a synergistic effect. After treating Populus purdomii seedling leaves infected with Melampsora larici-populina by the conidiospore suspension of the SynCome, the browning rate of uredinia significantly increased, with urediniospores being entangled by hyphae and cytoplasmic leakage, indicating strong biocontrol potential.

Conclusion The SynCome of endophytic Trichoderma strains (T1+T2+T4) can improve chitinase and β-1,3-glucanase activities to disrupt the cell walls of rust spores, thereby enhancing the biocontrol efficacy against blister rust and showing potential for forest disease management.