Pantoea–Bacillus as a Composite Microbial Community: Inhibition and Potential Mechanism Against Potato Anthracnose Disease

The potato (<i>Solanum tuberosum</i>), an important component of global food security, often faces threats from various diseases during its growth process, especially potato anthracnose (<i>Colletotrichum coccodes</i>), which severely affects crop yield and quality. In this study, we successfully isolated and identified two bacteria with potential for biological control, (<i>Pantoea agglomerans</i>) and (<i>Bacillus subtilis</i>). The experimental results indicate that the bacterial suspensions of strains JZ-1-1-1 and JZ-2-2-2 had a significant inhibitory effect on the pathogen ZL-7, with the inhibition rate of JZ-1-1-1 reaching as high as 55.21%. The inhibition rate of JZ-2-2-2 was 53.48%. When these two strains were mixed at a 4:6 ratio, the inhibitory effect on pathogenic bacteria was even more significant, reaching 68.58% inhibition. In addition, the composite microbial community produced biofilms with their yield gradually increasing within 24 h and showing a slight decrease after 72 h. The efficacy test further indicated that the composite bacterial suspension was highly effective in controlling the spread of lesions, with an efficacy rate as high as 81.40%. In the analysis of defense enzyme activity, peroxidase (POD) and superoxide dismutase (SOD) levels peaked on day seven, while the composite bacterial suspension significantly reduced malondialdehyde (MDA) and polyphenol oxidase (PPO) activity. Quantitative real-time PCR confirmed that these two strains effectively colonized the surface of potato tubers. In summary, this study provides an important theoretical basis and practical guidance for the application of biological methods for the prevention and control of potato anthracnose.