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Genetics

Genetics and Nature of Resistance to Race 2 of Sphaerotheca fuliginea in Cucumis melo PI 124111. Shmuel Cohen, Graduate student, Department of Life Sciences, Bar-Ilan University, Ramat-Gan 52100, Israel; Yigal Cohen, professor, Department of Life Sciences, Bar-Ilan University, Ramat-Gan 52100, Israel. Phytopathology 76:1165-1167. Accepted for publication 16 May 1986. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/Phyto-76-1165.

The inheritance of resistance to race 2 of Sphaerotheca fuliginea in Cucumis melo PI 124111 was studied in crosses with the susceptible cultivar Ananas Yokneam under greenhouse conditions. F₁ was intermediate based on gross appearance, but in terms of spore germination, colonies per cotyledon, and conidia per cotyledon was more like the resistant parent. When mildewed plants were classified susceptible and mildew-free plants were classified resistant, the F₂ progenies segregated 3 susceptible:1 resistant. Progenies from the backcross of the F₁ with the resistant parent segregated 1 susceptible:1 resistant, and those from the backcross of the F₁ with the susceptible parent were susceptible. We concluded that resistance to race 2 is conferred by an incompletely dominant gene. Resistance of PI 124111 to powdery mildew was attributed to reduced conidial germination of S. fuliginea on the leaf surface, reduced colony formation, and reduced sporulation in comparison to the susceptible parent, Ananas Yokneam.