Biocontrol potential of a rhizosphere-associated Bacillus amyloliquefaciens F2 isolate against Fusarium oxysporum f. sp. cubense Tropical Race 4 in Pakistan

Abstract

Fusarium wilt caused by Fusarium oxysporum f. sp. cubense is a serious fungal, soil-borne disease. It is also known as PANAMA disease, considered a major threat to the yield and quality of Banana worldwide. In this study, endophytic bacteria were isolated from soil, roots, and leaves of healthy banana plants growing in Fusarium oxysporum f. sp. cubense (Foc) tropical race 4 (TR4) infested soil. These endophytes were evaluated for their ability to inhibit the growth of Foc TR4. The results indicated that 7 out of 138 endophytic bacterial isolates showed significant inhibitory activity against mycelial development of F. oxysporum f. sp. cubense , with an inhibition rate of more than 50%. Isolate F2, which showed maximum inhibition (74%), showed 99.49% sequence identity with Bacillus amyloliquefaciens strain seq. S1 based on 16S rRNA sequence. Biological and PCR assays demonstrated that the isolate F2 promotes plant growth by actively producing indole-3-acetic acid, siderophore, ammonia, and hydrolytic enzymes, including protease, pectinase, amylase, catalase, cellulase, and chitinase. It expresses biocontrol-related genes, including surfactin, fengycin, iturin, bacillomycin, bacillibactin, bacillaene, subtilosin, macrolactin, yngG , yndJ , biotin, difficidin, and bacilysin. The genes surfactin, fengycin, iturin, and bacillibactin in this bacterial isolate are upregulated when it interacts with Foc TR4. It also produces various volatile compounds that may inhibit the growth of Foc TR4. These findings demonstrate that the F2 isolate could be a potential candidate for controlling Fusarium oxysporum f. sp. cubense in banana.