Evaluation of biocontrol potential of Egbenema aeruginosum against early blight in tomato production

Abstract

Tomato (Solanum lycopersicum L.) production in Kenya is increasingly threatened by early blight (Alternaria solani), a fungal disease that thrives in humid and greenhouse environments. Chemical fungicides, hitherto believed to be effective, raise environmental safety and pathogen resistance concerns. The objective of this study was to evaluate the biocontrol potential of Egbenema aeruginosum, a thermophilic cyanobacterium, against tomato early blight. Cyanobacterial isolates were cultured in BG-11 medium, identified via 16S rRNA sequencing, and applied as foliar spray at four concentrations (105, 106, 107 and 108 CFU ml-1) to the Kilele F1® tomato plants, in a greenhouse study. A commercial biological control product (Nopath) and an untreated control were the fungicides included. The tomato crops were grown for two cycles, from September to December 2024 and February to May 2025. The 107 CFU ml-1 treatment consistently showed the lowest disease severity score (mean = 1.3) and the highest fruit yield (3663.3 g per plant); while the untreated control recorded the highest severity (mean = 4.7) and the lowest yield (600 g per plant). There were significant differences (P < 0.05) across treatments. These results demonstrate that E. aeruginosum can effectively suppress early blight and enhance tomato fruit yield; providing a promising sustainable alternative to chemical fungicides in tomato production in Kenya.