Potential of Bacillus thuringiensis B9 and Bacillus pacificus B11 Isolated from Tomato (Solanum lycopersicum L.) Rhizosphere for Enhancing Groundnut (Arachis hypogaea L.) Production and Reducing Aflatoxigenic Aspergillus flavus Contamination

Context: Plant Growth-Promoting Rhizobacteria (PGPR) are crucial for enhancing plant nutrition and health. This study investigated the dual potential of PGPR as biocontrol agents to suppress aflatoxigenic Aspergillus flavus contamination in groundnut (Arachis hypogaea L.) and to concurrently improve crop growth and yield, addressing critical food safety and productivity challenges. Methodology: Two Bacillus strains, B. thuringiensis B9 and B. pacificus B11, isolated from tomato rhizosphere, were evaluated. In vitro antagonistic activity against aflatoxigenic A. flavus was assessed using vertical, circular confrontation and poisoned medium dual culture methods. A field trial was simultaneously conducted at astation, employing a Completely Randomized Block Design with four replications. Factors included two groundnut varieties (Grimari and Siksa) and four treatments (B. pacificus B11, B. thuringiensis B9, DAP+manure, and an untreated control). Growth and yield parameters were subsequently measured and statistically analyzed. Results: In vitro, B. pacificus B11 consistently inhibited aflatoxigenic A. flavus growth by over 50% across all methods, achieving the highest inhibition (83.9%) via circular confrontation. Field results demonstrated significant (p<0.05) differences among treatments for most growth and yield variables. Notably, B. pacificus B11 significantly improved groundnut performance regardless of variety, leading to a higher emergence rate (87.50%). Furthermore, this strain positively impacted pod number (40 per plant) and remarkably increased overall yield by more than 100% compared to the control. Conclusion: Bacillus pacificus B11 shows strong promise as a biofertilizer and biocontrol agent. Its capacity to enhance groundnut production while simultaneously reducing Aspergillus flavus contamination and potentially aflatoxin B1 contamination offers a sustainable alternative to chemical inputs, contributing to safer, higher-quality food production and reduced public health risks.