Profiling the bioactive metabolites of endophytic Bacillus involved in antagonistic interaction with the Fusarium pathogen of cowpea

Abstract

Fusarium wilt, caused by Fusarium oxysporum f. sp. tracheiphilum is a devastating disease that affects cowpea globally. Due to limitations and environmental concerns connected with the use of chemical fungicides, sustainable and eco-friendly alternatives, especially biocontrol with microbial agents have gained attention. Antagonistic bacterial endophytes that produce bioactive secondary metabolites can suppress pathogens, promote plant growth and induce systemic resistance, making them ideal choices for integrated disease management strategies. In this study, seventeen out of 38 endophytic bacteria isolated from cowpea demonstrated suppressive effect on the wilt pathogen. Bacillus velezensis CBRE5 and Bacillus amyloliquefaciens CBSE5 showed the highest mycelial growth inhibition. In vivo, their combined application significantly reduced wilt incidence and enhanced plant growth by improving yield. These two isolates were selected for GC-MS analysis to identify key metabolites responsible for their growth-promoting and biocontrol effects. A wide range of compounds belonging to diverse classes were identified. Bioactive metabolites such as 3-methyl-2-phenylindole; benzaldehyde, 2-chloro-3,4-dibenzyloxy; 1H-1,2,3-triazole-4,5-dimethanol,1-(phenylmethyl); and carbamic acid, N-(4-acetylphenyl), (3-tetrahydrothienyl) ester were recognized as potential antifungal agents. Docking studies further highlighted the interactions among these metabolites and four virulent protein targets of the pathogen. Among these, elongation factor 1-alpha exhibited the strongest interaction with 3-methyl-2-phenylindole (binding affinity −7.7 kcal/mol), followed by galacturonan 1,4-alpha-galacturonidase (binding affinity −7.4 kcal/mol). Benzaldehyde (2-chloro-3,4-dibenzyloxy) also displayed dual functional potential, effectively targeting elongation factor 1-alpha and endo-polygalacturonase. These in silico results are preliminary and serve to generate hypotheses about possible mechanisms of action of endophytic Bacillus. The findings support the biocontrol potential of endophytic Bacillus spp., providing a basis for their future application as eco-friendly agents in managing Fusarium wilt of cowpea.