Trichoderma guizhouense COTG-19 act as a potential biocontrol agent against Camellia oleifera anthracnose

Camellia oleifera anthracnose (COA) caused by Colletotrichum spp. is a major diseases impeding the sustainable development of C. oleifera in China. Chemical pesticides remain currently the primary control method, while long-term use poses significant risks to human health, environment and fungal resistance. Urgent action is needed to screen eco-friendly biocontrol agents against this disease. In this study, an Trichoderma strain COTG-19 was isolated from the roots of healthy C. oleifera plants, and identified as T. guizhouense combined with morphological and molecular characteristics. In the plate dual cultures assay, COTG-19 exhibited a notable inhibition rate against Colletotrichum strains that ranged from 71.89 % to 83.95 %. In addition, COTG-19 showed a strong preventive and therapeutic effects against COA, as determined with an in vitro leaf evaluation method. COTG-19 could produce chitinase, β-1,3-glucanase, lipase and protease to dissolve cell walls and membranes of pathogen. The volatile organic compounds (VOCs) produced by COTG-19 demonstrated significant inhibitory effects on mycelial growth. Scanning electron microscopy (SEM) and fluorescence microscopy revealed that COTG-19 producing-VOCs caused abnormal changes in mycelial ultrastructure and damaged the cell membrane integrity. Moreover, the VOCs obviously inhibited spore germination and completely blocked appressoria formation of C. fructicola. Using HS-SPME-GC-MS, 22 VOCs were identified, of which six were evaluated for antifungal activity against C. fructicola. 1-Octen-3-ol were identified as the primary antifungal VOCs. In addition, COTG-19 has a fungicide resistance advantage and can extensively endophytically in C. oleifera leaves as well as epiphytically on leaf surfaces, which traits helped sustain the strain's viability when used in nature settings. This study provides valuable insights into the potential application of Trichoderma biocontrol agents against C. oleifera anthracnose, contributing to the sustainable development of the C. oleifera industry.