Five hundred strains of rhizobacteria were isolated from the rhizosphere of the Central Highlands of Vietnam, where black pepper is cultivated. Of these, seven potent rhizobacteria were evaluated for anti-Phytophthora activity and 16S rRNA gene sequencing and phylogenic analysis classified. Evaluation of their antifungal activity was performed both in vitro and in vivo. The results showed that almost all potent rhizobacteria possessed anti-Phytophthora activity. The rhizobacteria strains displayed over 60% inhibition of Phytophthora during the in vitro test, and six rhizobacteria inhibited Phytophthora by 77.50–98.75% during the in vivo test. Enzymatic activities were measured to determine the antifungal mechanisms; these were identified as protease, chitinase, and β-glucanase. The effects of the rhizobacteria on plant growth and antifungal activity were also investigated. Under greenhouse conditions, black pepper seedlings treated with rhizobacteria were stronger and had lower rates of disease and fatality compared to the control group. The results from the in vitro test also showed that the anti-Phytophthora activity of the rhizobacteria was not dependent on enzyme activity, but rather on their chemical compounds. GC–MS and LC–MS profiles of the culture broth from the promising rhizobacteria strain RBDS.29 revealed seven potent antifungal compounds. The data suggest that Bacillus velezensis RB.DS29 is a promising rhizobacterium that promotes plant growth and the biocontrol of black pepper.
Research on Chemical Intermediates 45(11), p.5309-5323