CROSS-INFECTIVITY OF SPHAEROTHECA FULIGINEA TO WATERMELON, MELON, AND CUCUMBER

Powdery mildew has recently become a limiting factor in the commercial production of watermelon (Citrullus lanatus) in Israel.
Infection is widespread towards the end of the season regardless of the cultivar.
Microscopical examination of conidial shape and germination revealed that Sphaerotheca fuliginea is the causal agent of the disease.
Conidia collected from field-grown mildewed watermelon plants produced, upon inoculation in growth chambers, typical powdery mildew symptoms on watermelon, cucumber, Oriental pickling melon, squash, pumpkin, and bottle gourd, but not on melon or sponge gourds.
Conidia of S. fuliginea race 1 collected from cucumber and melon were infective only to the hypocotyls of watermelon, whereas conidia of race 2 from cucumber or melon failed to produce the disease on watermelon.
It is suggested that S. fuliginea of watermelon is forma specialis citrullus. Among 250 accessions of C. lanatus and C. colocynthis, only two were found to be resistant to this fungus.

VII Eucarpia Meeting on Cucurbit Genetics and Breeding

Y. Cohen, A. Baider, L. Petrov, L. Sheck, V. Voloisky

Citrullus, Cucurbitaceae, powdery mildew, resistance

https://doi.org/10.17660/ActaHortic.2000.510.14