Efficacy of Bacillus cereus as biocontrol agent against key fungal isolates of Soybean (Glycine Max [L.] Merril) seeds from three Agro-ecological zones in Nigeria

Abstract

ABSTRACT Soybean (Glycine max (L.) Merr.) has become increasingly important in industrial and culinary applications, cultivated across all continents. However, despite substantial growth in acreage and production, soybean productivity remains challenged by various diseases that can severely impact yield and quality. This study evaluated the effectiveness of Bacillus cereus as a biocontrol agent against key fungal pathogens affecting soybean seeds collected from Ibadan, Ikenne, and Kano. This study is aimed at identifying different B. cereus strain and identify the most aggressive strain of B. cereus from these locations. Seeds from five accessions were collected from three distinct agro-ecological zones in Nigeria, and fungal pathogens were isolated using PDA medium. Nine significant seed-borne fungi were identified through conventional and molecular methods: Botryodiplodia theobromae, Phomopsis sp., Fusarium verticilioides, F. oxysporum, Cercospora kikuchii, C. sojina, Sclerotium rolfsii, Macrophomina phaseolina, and Curvularialunata. The study employed a completely randomized design (CRD) to investigate the effects of B. cereus on seed-borne and seed-transmitted diseases in a screen house experiment. Each seed was treated with three B. cereus suspensions (106 CFU/ml), with three replicates conducted over two seasons. Biochemical tests and molecular characterization confirmed the three selected B. cereus strains, while in vitro assays demonstrated significant antagonistic effects against the pathogens. Notable differences (p ≤ 0.05) over 12 days indicated that the Kano isolate exhibited the highest aggressiveness compared to those from Ikenne and Ibadan. Analysis of variance revealed significant variations (p ≤ 0.05) among locations and treatments. The findings suggest that B. cereus effectively suppresses the growth of seed-borne and seed-transmitted pathogens in soybean, supporting its use as a biocontrol agent. Additionally, the study emphasizes the variability in biocontrol efficacy and aggressiveness among different B. cereus strains.