Bioprotective and biofertilizing effects of bacteria isolated from the melon rhizosphere: A sustainable strategy for controlling fusarium wilt and enhancing melon yield and quality

Melon Fusarium wilt is a major challenge to melon cultivation causing significant economic losses worldwide. While chemical fungicides are effective, concerns about food safety and environmental contamination have increased interest in eco-friendly alternatives with lower health risks for managing this pathogen. This study aimed to isolate, identify and evaluate the antifungal activity of bacteria from the melon rhizosphere against Fusarium oxysporum f. sp. melonis and to assess their impact on melon yield and quality under greenhouse and field conditions. In vitro confrontation assays revealed that eight bacterial isolates exhibited significant antagonistic activity compared to the control. The highest inhibition rate, 73.31 % was recorded for Bacillus thuringiensis (PP827365) after three days of incubation. Inoculating melon plants with these identified isolates, particularly B.thuringiensis, significantly enhanced growth, as evidenced by increases in leaf area (≥23.3 %), stem (≥78.3 %), and root biomass (≥85.7 %), along with improved yields (≥69.5 %), fruit quality (firmness (≥87.9 %) and Brix (≥31.2 %)) and reduced Fusarium wilt severity (≥60.1 %). These improvements were attributed on the one hand to the ability of these isolates to enhance hydro-mineral and carbon nutrition, as indicated by increased water (≥32.3 %), potassium (≥91.7 %), phosphorus (≥207.4 %), calcium (≥113.3 %), sugar (≥30.7 %), and chlorophyll (≥52.4 %) contents. On the other hand, to effective management of Fusarium wilt, as evidenced by reduced MDA (≥39.8 %), proline (≥59.9 %), and electrolyte leakage (≥33.8 %), along with increased peroxidase (≥74.4 %), polyphenol oxidase (≥88.2 %), and leaf protein levels (≥177 %). These findings suggest that B.thuringiensis could serve as a promising sustainable strategy for managing Fusarium wilt and boosting melon yields.