Identification of Fusarium solani f. sp. cucurbitae Causing Zucchini Fruit Rot in Inner Mongolia, China

Fruit rot is one of the major diseases impacting the production and quality of zucchini (Cucurbita pepo). In August 2021, fruit rot symptoms were observed on the zucchini fruit 'Jindi 1' in the Wuyuan region in Inner Mongolia, China with an incidence ranging from 10% to 30%. Where the pepo was in contact with the soil, dark grey and spongy corky lesions 4-5 cm in diameter with a light brown halo were observed. The internal necrosis of the fruit rind was also recorded. From the affected fruits, fungal colonies belonging to the Fusarium species were exclusively isolated. Molecular analysis of the ITS, TEF-1 alpha, and RPB2 sequences identified the isolates as Fusarium solani f. sp. cucurbitae. Inoculated on 'Jindi 1', the strain Fx-1a induced typical fruit rot on the pepo and wilting on seedlings, while negative-controls remained asymptomatic. The impact of this disease on seed quality and yield in zucchini seed production needs to be further studied.