Antifungal activity of Bacillus sp. against Colletotrichum causing anthracnose in postharvest banana fruits

One of the worst banana diseases is anthracnose due to many species of Colletotrichum, which influences fruit quality and decreases shelf life. Therefore, this study was conducted to elucidate the antagonistic activity of Bacillus sp. against Colletotrichum causing anthracnose on postharvest bananas. In this study, 10 fungal isolates were obtained from 12 samples of postharvest banana fruits infected with anthracnose. Bananas infected with strain COL4 (identified as Colletotrichum gloeosporioides) based on mycelium characteristics, conidial morphology, and internal transcribed spacer sequence analysis, satisfied Koch's postulates, with disease symptoms similar to those of naturally infected bananas. This study also isolated 25 strains of Bacillus from banana rhizosphere soils in Vinh Long Province, Mekong Delta. The findings demonstrated that 8 isolated strains exhibited spore inhibitory effects and that 9 isolates displayed mycelial antagonistic effects. Among them, strains M6, NA2, NA3, N5, N13, and L2 showed the strongest spore inhibition and mycelial antagonistic activities. Additionally, the bacterial strains studied also exhibited amylase, cellulase, protease, and chitinase activities. The results of 16S rRNA gene sequencing showed that NA2 and NA3 strains had a high identity with Bacillus in GenBank (>99%). The current findings show the potential application in post-harvest preservation of bananas of isolated bacterial strains in the future.