Exploring the antagonistic mechanism of Bacillus atrophaeus CY1 for the biological control of potato common scab.

Streptomyces scabies is a pathogenic actinomycete that infects potato crops and commonly causes scab-like lesions on potato tubers. Screening of strains antagonistic towards S. scabies in the natural environment was performed in this study. This study focused on the extraction of antibacterial substances and changes in potato defense enzymes and the rhizosphere microbiota. Together, these factors constitute biological control mechanisms. Pot experiments showed that Bacillus atrophaeus CY1 reduced the infection of scabs caused by S. scabies from 92 % to 60 % and the disease index from 62 % to 25 %. Scanning electron microscopy analysis revealed that B. atrophaeus CY1 repressed the growth of S. scabies by disrupting the mycelium and affecting potato defense enzymes. Compared with the infected group, catalase, peroxidase, and polyphenol oxidase activities in potato tubers of the co-culture group increased by 21.98 %, 71.49 %, and 116.15 %, respectively, and SOD activity decreased by 4.9 %. Moreover, at different developmental stages, the microbiota counts in the CY1 cocultured groups were significantly higher, and the actinomycete count was considerably lower. At the budding stage, urease activity was 13.39 mg g-1 in the co-culture group, representing an increase of 37.37 % and 20.62 %, respectively, compared to the control group. Cellulase activity in the SC group was 0.675 mg-1, which represented increases of 39.18 % and 43.92 %, respectively. These results demonstrate that B. atrophaeus CY1 is a potential candidate for the biological control of S. scabies.