Identification and Characterization of Fusarium incarnatum Causing Leaf Spot and Fruit Rot on Luffa in China

In 2022, an outbreak of fungal rot disease affected luffa crops in Shanghai and Zhejiang Province. Infected plants exhibited symptoms including yellowing, chlorosis, wilting, and water-soaked occurred on leaves and fruits. Dark brown, concave lesions developed, often accompanied by white or pale pink mold under moist conditions. Fourteen pathogen strains, morphologically resembling Fusarium species, were isolated. Molecular analysis confirmed Fusarium incarnatum as the causative agent. Pathogenicity tests on luffa plants fulfilled Koch's postulates, with inoculated plants displaying the same symptoms. Re-isolation of the fungus from the inoculated plants confirmed its role in the disease. To our knowledge, this is the first report of F. incarnatum causing leaf spot and fruit rot on luffa in China. Moreover, the soil bacterial strain Bacillus velezensis BV171 displayed strong inhibition of F. incarnatum mycelia growth and promoted the growth of sponge gourd plants. These findings lay the foundation for the development of diagnostic tools, disease management strategies, and the breeding of resistant luffa varieties.