Inheritance of Resistance to Downy Mildew in Cucumis melo PI 124112 and Commonality of Resistance Genes with PI 124111F. David Kenigsbuch, Graduate Student, Department of Life Sciences, Bar-Ilan University, Ramat-Gan 52900, Israel. Yigal Cohen, Professor, Department of Life Sciences, Bar-Ilan University, Ramat-Gan 52900, Israel. Plant Dis. 76:615-617. Accepted for publication 29 October 1991. Copyright 1992 The American Phytopathological Society. DOI: 10.1094/PD-76-0615.

The monoecious, downy mildew-resistant Cucumis melo PI 124112 was made homozygous for resistance by selfing and screening for seven generations and crossed with either the downy mildew-susceptible cultivar Ananas-Yokneam (AY) or the downy mildew-resistant breeding line PI 124111F (possessing the resistance genes Pc1 and Pc2). F₁, F₂, BCs, and TC progeny plants were inoculated with Pseudoperonospora cubensis pathotype 3 and assessed for reaction type 8 days postinoculation. Progenies of the cross PI 124112 × AY segregated in a manner supporting the hypothesis that resistance in PI 124112 was conferred by two partially dominant genes. Progenies of the cross PI 124112 × PI 124111F segregated in a manner supporting the hypothesis that PI 124112 shares one common gene (Pc1 or Pc2) with PI 124111F and another, newly assigned gene, Pc4. The lack of identity of the genes from these germ plasm lines means that the level of downy mildew resistance may be improved in newly developed muskmelon cultivars.

Keyword(s): Cucurbitaceae, genetics.