Using bacterial endophytes to treat Fusarium-induced seedling wilt in Sorghum bicolor under abiotic stress

Sorghum (Sorghum bicolor) is the fifth-most grown crop in Africa and plays a prominent role in the culture and diet of African countries including Ethiopia, South Africa, Kenya, and Egypt. While well-adapted to the African climate, sorghum is highly susceptible to the fatal fusarium wilt, caused by the fungal pathogen Fusarium oxysporum, which can lead to crop losses of up to 30%. Treatments have historically centered around practices such as hybridization and fungicides. Due to recent biotechnological advances, scientists have become interested in endophytes—microscopic organisms that form symbiotic relationships with the host plant—as a more sustainable alternative. However, current research has investigated the endophytic biocontrol behavior of Fusarium under only ideal moisture, temperature, and nutrient levels in vitro. A major gap therefore exists with regard to endophytes’ effectiveness under suboptimal field conditions. Therefore, in this study, the two bacterial endophytes Bacillus subtilis and Pseudomonas fluorescens were inoculated with Fusarium oxysporum in Petri dishes and in sorghum plants under simulated abiotic conditions to determine if endophytes could still be successfully applied under suboptimal conditions for possible field implementation. Furthermore, because Fusarium oxysporum can be transmitted to sorghum seedlings via contaminated soil and insect feeding, this study assessed the efficacy of endophytes in controlling Fusarium present in the soil and injected into plant stems. In vitro, both endophytes significantly limited Fusarium growth; in planta, only Bacillus subtilis was found to be effective in limiting fusarium wilt.