Effects of a Mixture of Brevibacillus brevis with Other Bacillus sp. Strains against Gray Mold and on Enzyme Activities of Grape

Abstract

Gray mold disease, caused by Botrytis cinerea, has reduced grape’s output and market quality globally. In this study, the antifungal activity of a mixed microbial combination of Brevibacillus brevis FJAT-0809-GLX and Bacillus sp. strains was investigated. The results showed that the inhibition rate against B. cinerea was 85.10% when B. brevis FJAT-0809-GLX was mixed with a mixture of B. brevis FJAT-10623 and Bacillus velezensis FJAT-55034 at a proportion of 80%:20%, which was significantly higher than those of other combination proportions. The inhibitory rates of the mixed microbial combination diluted 0 times, 10 times, and 100 times were 89.14%, 88.10%, and 86.33%, respectively, with no significant differences between each other. The mixed microbial combination appeared to be temperature-insensitive and significantly stable from pH 3 to pH 7. Furthermore, it was discovered that its antifungal activity was significantly stable with UV radiation for 30 min, 60 min, and 90 min, with values of 84.82%, 83.89%, and 82.22%, respectively. An amount of 0.025 mol mL−1 of KCl, CuSO4, and MgCl2 had no effects on the antifungal activity of the mixed microbial combination, while 0.025 mol mL−1 of NaCl, ZnSO4, FeSO4, CaCl2, and MnSO4 reduced the inhibition rate. The mixed microbial combination demonstrated antifungal activities against a variety of fungi, with inhibition rates ranging from 68.78% to 85.10%. The grape fruits and grape leaves treated with the mixed microbial combination decayed at 27.27% and 48.34%, respectively. Additionally, the mixed microbial combination improved grape fruit resistance by increasing the activity of defense enzymes polyphenol oxidase (PPO) and catalase (CAT). Therefore, the results indicated that the mixed microbial combination had great biocontrol potential against gray mold in grape fruits.