Abstract: The tea industry is one of China's important agricultural economic resources. However, widespread outbreaks of anthracnose on Camellia sinensis pose a significant threat to the sustainability of the tea industry. Conventional approaches based on chemical pesticides face inherent challenges, including pesticide residue accumulation and environmental pollution. In this study, the biological control effect of Bacillus velezensis YJK1 on tea tree diseases was evaluated. The results demonstrat that the YJK1 isolate exhibited robust antagonistic activity against fungal diseases affecting tea trees, particularly against pathogens such as Colletotrichum camelliae, Colletotrichum fructicola and Fusarium fujikuroi. YJK1 fermentation diluent has a significant inhibitory effect on the spores of C. camelliae and C. fructicola. The inhibitory effects of YJK1 fermented liquid on the diameter of C. camelliae were evaluated with the detached tea leaves. YJK1 fermented liquid effectively prevented tea tree anthracnose with 78.1% control when applied 24 h before C. camelliae inoculation and 61.8% during simultaneous inoculation. However, its efficacy was limited (post-inoculation). The YJK1 fermentation broth has a broad-spectrum of activity against various fungi. The antagonistic activity of the fermented liquid was stable below 80 ℃. After 60 min of UV treatment, the inhibition rate was still above 50%. And after treatment with different pH values, there was no significant difference in the inhibition rate within the pH range of 5-11. These findings suggest that B. velezensis YJK1 is a promising biocontrol agent for the management of tea plant diseases.

Key words: Bacillus velezensis, tea anthracnose, antagonistic bacteria, biological control, stability