Biocontrol Potential of Plant Growth Promoting Rhizobacteria against Fusarium oxysporum in Pepper Plants

Abstract

Aim: This study aimed to examine the biocontrol potential of plant growth-promoting rhizobacteria previously isolated from the tomato rhizosphere against Fusarium oxysporum in pepper plants. Place and Duration of Study: This study was conducted at the Microbiology Laboratory of the Federal University, Oye-Ekiti, between July 2025 and May 2026. Methods: Isolates were obtained from stock cultures and screened for key plant growth-promoting traits, including ammonia, siderophore, nitrogen fixation, and amylase production. Phytopathogenic fungi were isolated from apparently diseased tomato plants. The antifungal activity of the rhizobacterial isolates was evaluated using a dual-culture method. The greenhouse experiment was conducted using a completely randomised block design. Results: Each of the five bacterial isolates exhibited important plant growth-promoting characteristics. Throughout the investigation, isolate IS4A produced the greatest increase in plant height, reaching more than 35 cm by Week 8. By Week 8, isolate IS9 had reached approximately 30 cm, representing the second-highest growth promotion. The highest percentage inhibition of Fusarium was recorded for isolate IS14B (56%), followed by IS13 (47%), IS4A (45%), IS9 (27%), and IS10 (24%). Among all groups, pathogen-inoculated plants (Control 1: Fusarium only) had the lowest fresh weight (5.21 g) and dry weight (0.42 g). IS9 recorded the greatest biomass accumulation, with a fresh weight of 32.12 g and a dry weight of 8.16 g, more than three times the healthy baseline (Control 2: 9.39 g fresh weight and 2.38 g dry weight). Conclusion: The present findings indicate that Pseudomonas lactis and Bacillus tropicus have potential as biological control agents against Fusarium oxysporum while simultaneously promoting pepper growth.