Biocontrol potential of Bacillus and Pseudomonas species against Fusarium oxysporum, a causative agent of chili pepper wilt disease in Ethiopia

Fusarium wilt, a vascular disease caused by Fusarium oxysporum, poses a significant threat to chili pepper production both in Ethiopia and globally. Chemical fungicides have shown limited efficacy, primarily because symptoms emerge only after the pathogen has infiltrated the plant’s vascular system, making early intervention difficult. Moreover, reliance on chemical fungicides raises concerns about environmental contamination and potential health hazards. In contrast, while biological control offers a promising alternative, imported biocontrol agents often underperform under field conditions due to poor ecological adaptation to local environments. Thus, the objective of this study was to evaluate the potential of locally screened Bacillus and Pseudomonas spp. against F. oxysporum under field conditions in Ethiopia. Four biocontrol agents were evaluated on two varieties of chili pepper (Ma. Fana and Ha. Zala) in two sites using a complete randomized block design (RCBD). Overall, the study found that the evaluated biocontrol agents decreased wilt disease severity on chili pepper by about 66.4% while increased dry pod yield by 19.84%. Specifically, the biocontrol agent ‘Bio_7F’ strongly decreased the disease by about 71%, followed by ‘Bio_6F’ (68%), ‘Bio_4F’ (64.8%), and ‘Bio_5F’ (61.9%) at both study sites. Furthermore, these isolates increased leaf number by 20.81%, seed germination rate by 16.5%, and shoot length by 17%, while they decreased disease incidence by about 61.3%. Codes ‘Bio_7F’, ‘Bio_6F’, and ‘Bio_5F’ belonged to the Bacillus, while ‘Bio_4F’ was from Pseudomonas. The analysis of variance revealed that biocontrol agents, study locations, and varieties interacted significantly (P < 0.001) to affect disease severity and dry pod yield. Thus, locally screened Bacillus and Pseudomonas spp. could serve as effective biological control agents in managing wilt disease in chili pepper.