Biocontrol potential of Bacillus subtilis IBFCBF-4 against Fusarium wilt of watermelon

Abstract

Fusarium wilt of watermelon caused by Fusarium oxysporum f. sp. niveum (FON) is a destructive soil-borne disease. The objective of this study was to screen antagonistic bacteria with potential applications for controlling this disease. Strain IBFCBF-4 with obvious antifungal activity against FON and seven other phytopathogens was successfully isolated from a rhizosphere soil. Based on the morphological, physiological, biochemical characteristics and 16S rDNA sequence analysis, IBFCBF-4 was identified as Bacillus subtilis. Under greenhouse condition, IBFCBF-4 could significantly reduce the incidence of Fusarium wilt of watermelon by 51.1% compared to the control. The studies on the antagonistic mechanism showed that IBFCBF-4 could cause abnormal swelling and increased branching to the hyphae of FON. Meanwhile, the volatile and non-volatile compounds produced by IBFCBF-4 were able to suppress the mycelial growth of FON. Furthermore, PCR analysis confirmed the presence of ituA, ituB, ituC, ituD, bamD, bmyB, fenB, srfAB, surf, bacA, bacD, bacAB, tasA, mrsA and mrsM genes involved in the biosynthesis of iturin A, bacillomycin, fengycin, surfactin, bacilysin, tasA and mersacidin, respectively. Taken together, B. subtilis IBFCBF-4 can be used as a potential biocontrol agent against Fusarium wilt of watermelon, but further work is required to improve its efficacy.