Origin of Fusarium Wilt Resistance in Texas AES Muskmelon Cultivars. F. W. Zink, Plant Breeder Emeritus, Department of Vegetable Crops, University of California, Davis 95616. Plant Dis. 75:24-26. Accepted for publication 7 May 1990. Copyright 1991 The American Phytopathological Society . DOI: 10.1094/PD-75-0024.

The mode of inheritance of resistance to Fusarium wilt, caused by Fusarium oxysporum f. sp. melonis race 2, in muskmelon (Cucumis melo) cvs. Mango Melon and Smith’s Perfect and in Texas AES (TAES) cvs. Rio Gold, Wescan, and Dulce was determined by analyzing wilt resistance segregation of F₁, F₂, and BC₁ populations of crosses with susceptible cv. Top Mark. The ratios obtained indicate that resistance to race 2 in these cultivars is conferred by a dominant gene. In allelism tests, resistance in Mango Melon, Smith’s Perfect, and the TAES cultivars was determined to be controlled by the gene Fom 3, or an allele of this gene, which also confers resistance in Perlita. Mango Melon, Smith’s Perfect, and the TAES cultivars were resistant to race 2 at inoculum concentrations of 0.5 × 10⁶ spores per milliliter and susceptible at 1.0 × 10⁶. Circumstantial evidence indicates that Fusarium wilt resistance in Rio Gold, Wescan, Perlita, and Dulce stems from the Fusarium wilt-resistant Mango Melon and Smith’s Perfect. Resistance to downy mildew, caused by Pseudoperonospora cubenis, was introduced into the TAES cultivars from Smith’s Perfect. It is proposed that the breeders were not aware of Fusarium wilt resistance in their breeding lines or cultivars and that the gene Fom 3, or an allele of this gene, is associated with the downy mildew resistant trait and was incorporated into the TAES cultivars during the selection for downy mildew resistance.