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Epifluorescence Microscopy of Sphaerotheca fuliginea Race 2 on Susceptible and Resistant Genotypes of Cucumis melo. Yigal Cohen, Professor, Department of Life Sciences, Bar-Ilan University, Ramat-Gan 52100, Israel; Helena Eyal, Senior technician, Department of Life Sciences, Bar-Ilan University, Ramat-Gan 52100, Israel. Phytopathology 78:144-148. Accepted for publication 16 July 1987. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/Phyto-78-144.

Fungal growth and host response were investigated in leaves of susceptible, moderately resistant, and resistant genotypes of muskmelon with the aid of the fluorescent stain calcofluor, using ultraviolet epifluorescence microscopy. Fungal germination at 24 hr with a single germ tube proceeded equally well on all genotypes, but the production of the second and third germ tubes at 48 hr, hyphal growth, and sporulation were inhibited in resistant genotypes, probably because of the hypersensitive reaction of epidermal cells that was associated with germ tubes and hyphae. The possibility is raised that the resistant genotypes studied share a common gene with PI 124111 for resistance to race 2 of Sphaerotheca fuliginea.

Additional keywords: genetics, powdery mildew.