Biocontrol ability and possible mechanism of Bacillus velezensis LQ-03 against Colletotrichum scovillei, the pathogen of anthracnose on chili pepper.

BACKGROUND Pepper anthracnose caused by Colletotrichum scovillei is a destructive disease. Currently, anthracnose diseases are primary controlled using fungicides, but prolonged overuse of conventional chemical fungicides can adversely affect both the environment and human health. Thus, it is essential to explore safer alternative methods for controlling pepper anthracnose to mitigate environmental and food safety risks. One promising strategy is biocontrol utilizing Bacillus species. RESULTS We identified the Bacillus velezensis strain LQ-03, which demonstrated significant antagonistic activity against C. scovillei and various other plant pathogens. LQ-03 exhibited effective control of pepper anthracnose and enhanced the activities of defense enzymes in pepper fruit. The crude protein extracts of LQ-03 significantly inhibited mycelial growth, conidial germination and viability, disrupted the morphological structure and cell membrane integrity, and induced reactive oxygen species (ROS) accumulation in C. scovillei. The crude protein extracts effectively reduced the progression of anthracnose on pepper fruit. Transcriptome analysis revealed that the extracts exert antifungal activity by reprogramming multiple metabolic pathways, particularly those involved in energy conversion. Several biosynthetic gene clusters (BGCs) potentially responsible for the synthesis of bioactive compounds were predicted from the LQ-03 genome. CONCLUSION Our results showed that LQ-03 is a promising biocontrol agent against anthracnose caused by C. scovillei in pepper, providing a theoretical basis for development as a natural fungicide. © 2025 Society of Chemical Industry.