Exploration and evaluation of native bacterial antagonist against Fusarium wilt disease (Fusarium oxysporum f.sp. cubense Tropical Race 4) in banana (Musa spp.)

Abstract

An experiment was conducted during 2022 and 2023 at ICAR-National Research Centre for Banana, Tiruchirappalli, Tamil Nadu to isolate and assess native rhizospheric and endophytic bacterial strains for their potential biocontrol activities against Fusarium oxysporum f.sp. cubense Tropical Race 4 (Foc TR4) causing wilt in banana (Musa spp.). A total of 75 bacterial strains, comprising 50 endophytic and 25 rhizospheric isolates, were obtained from various parts of banana plants and their rhizospheric soils. The experiment was laid out in a completely randomized block design (CRBD) with six treatments and five replications. In-vitro screening revealed that Bacillus subtilis (Ple-3 and Kr-2), Bacillus subtilis (Ykmr-6), Pseudomonas fluorescens (Por-4), and Bacillus velezensis (Toe2) significantly inhibited spore germination (93.43–100%) and mycelial growth (67–78%) of Foc TR4. These isolates demonstrated biocontrol activities, including HCN production, chitinase and protease activity, as well as phosphate solubilization, thereby enhancing their biocontrol potential. Molecular analysis confirmed their identity as Bacillus spp. and Klebsiella spp. and sequences were deposited in GenBank (OR472994 to OR472998). Combined soil application of Bacillus subtilis (Ykmr-6) + Pseudomonas fluorescens (Por-4) reduced internal wilt score in tissue-cultured banana plants. A lowest internal wilt score 0.8 (average of two seasons) was observed to be most effective in reducing internal wilt scores in tissue-cultured banana plants cv. Grand Nain. The study highlights the potential of bacterial strains, Bacillus subtilis (Ple-3 and Kr-2), Bacillus subtilis (Ykmr-6), Pseudomonas fluorescens (Por-4), and Bacillus velezensis (Toe2) as biocontrol agents, providing an alternative to chemical methods in managing Fusarium wilt in bananas and paving the way for integrated disease management strategies in banana cultivation.

Keywords

• Banana, Bacterial biocontrol agents, Characterization, Disease management, Fusarium oxysporum f.sp. cubense TR4, Wilt