Actinomycete as biocontrol agents against tomato gray mold disease caused by Botrytis cinerea

Abstract

The present work aims to isolate actinomycete bacteria with antagonistic abilities towards Botrytis cinerea, the causal agent of gray mold, from a soil sample collected from the rhizosphere of a healthy tomato grove. In vitro confrontation led to the isolation of 104 actinomycete isolates; fifteen isolates have shown the most significant mortality rate of the mycelial growth of B. cinerea (>50%). Based on the results of this screening, representative strains were selected to verify their in vivo antagonistic activity on tomato fruits; the reduction of B. cinerea has a percentage ranging from 52.38% to 96.19%. Furthermore, the actinomycete isolates were evaluated for their plant growth-promoting (PGP) properties and their ability to produce biocontrol-related extracellular enzymes viz., amylase, protease, cellulase, chitinase, esterases, and lecithinase. Indeed, Ac70 showed high β-1,3-glucanase activity and siderophore production (17U/ml and 43% respectively), and the highest chitinase activity (39μmol/ml) was observed for Ac24. These results indicated that these actinomycetes might potentially control gray mold caused by B. cinerea on tomato fruits. Investigations on enhancing the efficacy and survival of the biocontrol agent in planta and finding out the best formulation are recommended for future research.