Potential antagonistic rhizobacteria to control Colletotrichum scovillei, the cause of anthracnose disease in chili pepper

Six species of Colletotrichumwere identified as the cause of anthracnose disease on Bali Island, Indonesia in 2018. These species were C.scovillei, C. acutatum, C. nymphaeae,C. gloesporioides, C. truncatum, and C. fructicola. Among them, C. scovilleiwas the most prevalent at 55% of all samples tested. This study was conducted to find potential antagonistic rhizobacteria isolated from various rhizospheres of plants grown in Bali. A total of 1,040 rhizobacteria isolates were tested for their antagonistic activity against the growth of C. scovilleion potato dextrose agar. Results showed that10 isolates inhibited the growth of C. scovilleiby more than 80%. Among these isolatesC1 and C7B possessed inhibitory activity at 94.9% and 94.3%, respectively. Molecular identification based on analysis of 16S rRNA gene showed that isolate C1belonged to the species Paenibacillus polymyxa, whereas isolateC7B was identified as Bacillus siamensis. According to scanning electron serious damage on mycelia of C. scovilleiwas observed. Wrinkles were observed on mycelia of C. scovilleigrown jointly with rhizobacterial isolate C1, whereas no wrinkle was observed on C. scovilleigrown solely. Three compounds were detected in the hexane phase of cell-free filtrate P.polymyxaC1, namely, 3-hydroxy-2-butanone and 2,3-butanediol. These compounds may be responsible for antifungal activity against C. scovillei