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Interactions of Microsphaera diffusa with Soybeans and Other Legumes. Julia S. Mignucci, Graduate Student, Department of Plant Pathology, University of Illinois, Urbana, IL 61801; D. W. Chamberlain, Emeritus Professor of Plant Pathology, Department of Plant Pathology, University of Illinois, Urbana, IL 61801. Phytopathology 68:169-173. Accepted for publication 28 July 1977. Copyright 1978 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-68-169.

Conidia of Microsphaera diffusa produce as many as five germ tubes upon germination. Only the first germ tube forms an appressorium. The conidium is the center of the mildew colony and a conidiophore can arise directly from it. Development of the fungus from germination of conidia to production of conidia was followed at 3- and then 12-hr intervals. Twenty-one members of the 35 Leguminosae tested were hosts of the fungus. Different degrees of infection on susceptible plants were evident not only between species but also between cultivars of the same species. These hosts showed one or more of the following symptoms: curling of leaves, wilting, defoliation, chlorosis, necrosis, water-soaked lesions, earlier senescence, shriveled seeds, and incomplete pod filling. The production of conidiophores and conidia were inhibited in Flambeau but not in Acme soybeans.

Additional keywords: histology, host range, symptomatology, asexual cycle, resistance.