Common bean is a major grain legume worldwide. It serves as an excellent source of dietary protein. Fusarium wilt disease caused by Fusarium oxysporum limits the production of common bean. Indiscriminate agricultural practices such as irrigation with brackish water, excessive use of chemical fertilizers and pesticides as well as mining activities are significant sources of toxic metals. Vanadium plays an important part of South Africa mining industry. In high concentrations in the soil, vanadium negatively impact plant growth and development. Furthermore, the combined effect of vanadium stress and F. oxysporum infection may result in a more severe effect, posing a serious concern for common bean production and food security.
Therefore, the present study aimed to harness the potential of plant endophytes in providing protection against F. oxysporum infection while simultaneously enhancing heavy metal stress tolerance in common bean. In this study, among 60 endophytic bacteria isolated from different plant species thriving in soils naturally rich in vanadium, Klebsiella sp. exhibited the highest plant growth-promoting traits, i.e. siderophore and indole-acetic acid production, zinc, and phosphate solubilization. In addition, dual-culture plates demonstrated the ability of Klebsiella sp. to inhibit the growth of F. oxysporum. Furthermore, plants that were inoculated with Klebsiella sp. prior to vanadium treatment showed better growth (i.e. higher shoot and root biomass) when compared to the uninoculated controls, demonstrating the bacterium’s ability to enhance the growth of common bean under vanadium stress. These findings demonstrate the potential of plant endophytes in mitigating stress-related harm to plant growth.