Biocontrol activity of yeast and AM fungi against Fusarium oxysporum f. sp. Lycopersici

Fusarium oxysporum f. sp. lycopersici, the causal agent of Fusarium wilt in tomato, posed a significant threat to tomato cultivation. This study investigated the biocontrol potential of yeast isolates and Arbuscular Mycorrhizal Fungi (AMF) against this pathogen. Soil and phyllosphere samples were collected from tomato fields in Tamil Nadu, India, leading to the isolation of 120 yeast strains using serial dilution and leaf imprinting techniques. Morphological characterization grouped the isolates with 35 unique colonies were selected for further analysis. Molecular characterization identified three key yeast isolates: Rhodosporidium toruloides (Y2), Moesziomyces antarcticus (Y14) and Pichia kudriavzevii (Y16). Under pot culture conditions, the combined application of AMF and yeast isolates significantly reduced Fusarium wilt incidence. Treatment T5 (AMF liquid-based inoculum + soil yeast Y14) exhibited the highest root colonization (86.66 %), maximum spore load (10397 spores) and minimal disease incidence (11 %), with an 89 % disease reduction compared to the control. This treatment also enhanced tomato plant growth metrics, including height (121.00 cm), root length (61.10 cm) and antioxidant enzyme activity (peroxidase: 0.392 min/g, polyphenol oxidase: 0.791 min/g). Yield parameters were also improved, with maximum fruit weight (19.45 g) and fruit count (6.24) observed in T5-treated plants.