Antifungal and plant-growth promoting potency of Streptomyces rochei against biotic stress caused by Race 4 Fusarium wilt on banana

Abstract

Banana is a staple food for millions of individuals, especially in regions with tropical and subtropical climates. Nevertheless, the cultivation of banana is under significant threat from Fusarium wilt, a harmful biotic stress transmitted through the soil and caused by Fusarium oxysporum f. sp. cubense (Foc). This disease has the potential to devastate and infect almost all the varieties of bananas, especially with the emergence of Foc race 4. This study investigates the possibility of Streptomyces rochei AMBEAROOT2, isolated from the banana, used as a biocontrol agent against Fusarium wilt in banana. The molecular characterization of ten Foc isolates identified Fusarium oxysporum f. sp. cubense TFOC6 as the most virulent and confirmed as race 4. S. rochei AMBEAROOT2 exhibited significant mycelial inhibition (62.3%) of F. oxysporum f. sp. cubense TFOC6 and plant growth-promoting characteristics, including indole-3-acetic acid, biofilm formation, and exopolysaccharide synthesis. Gas Chromatography-Mass Spectroscopy analysis identified metabolites produced by S. rochei AMBEAROOT2, with molecular docking investigations revealed strong binding affinities of compounds viz., 3-phenyl-3-p-tolyl-1-(2,4,6-trimethyl-phenyl)-propane-1-one, 19-acetoxy-4,4-dimethyl-, oxime, Androst-5-en-3-one, and Pyrano [4,3] benzopyran-1,9-dione to key virulence proteins (Catalase-peroxidase, Kynureninase, Penta functional AROM polypeptide, and Ribose phosphate pyrophosphokinase) of Foc. In greenhouse conditions, micro-propagated banana plantlets treated with S. rochei AMBEAROOT2 demonstrated enhanced growth, improved physiological traits, and higher levels of defense enzymes compared to those inoculated with F. oxysporum f. sp. cubense TFOC6 alone. It also induced systemic resistance and a 100% decrease in the incidence of Fusarium wilt. In conclusion, S. rochei AMBEAROOT2 showed potential antifungal activities, promoted plant growth, and could be used to manage wilt disease in banana after field evaluation.