Investigating plant growth promoting and antifungal potential of Metarhizium spp. against Fusarium wilt in tomato

Fusarium oxysporum f. sp. lycopersici, , the causal agent of tomato Fusarium wilt, is an important soil-borne pathogen responsible for severe losses and reduction in total yield both in fields and in greenhouses. While fungicides are, the most effective, prolonged use raises concerns about human health and environmental burdens. This research aimed to investigate the inhibitory effect of Metarhizium spp. against Fusarium wilt disease under laboratory and greenhouse conditions. The results revealed that Metarhizium sp. Me351 could produce indole-3-acetic acid and produce hydrolytic enzymes (beta-1,3-glucanase, pectinase, and catalase). Similarly, significant bio-- control efficacy was observed, with reductions of up to 0.3 cm in diameter achieved by Metarhizium sp. Me351 in terms of inhibiting the mycelial growth of pathogenic fungi under laboratory conditions. This translates to a 6.98% decrease in F. oxysporum f. sp. lycopersici growth relative to the untreated control (100%). In greenhouse trials, preventive treatments using Metarhizium sp. Me351 enhanced tomato seedling growth compared to the positive control. Increases were ob-- served in various parameters: 66.81% (plant length), 27.15-11.85% (fresh and dry weights of the aerial part system), 49.18% (root length), and 55.74-12.64% (fresh and dry weights of the root system). Additionally, tomato plants treated with Metarhizium sp. Me351 and inoculated with pathogenic fungi showed significant increases in chlorophyll a (2.77 mg g-1 fresh weight), b (1.24 mg g-1 fresh weight), and total chlorophyll content (4.01 mg g-1 fresh weight). This treatment also exhib-- ited heightened activity levels of catalase, peroxidase, superoxide dismutase, polyphenol-oxidase, and total phenolic content. The minimum disease severity index (18.33%) was recorded under this treatment condition. It was concluded that Metarhizium sp. Me351 can potentially be used to reduce Fusarium wilt and promote plant growth of tomato.