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Nutrition during Spore Production and the Inoculum Potential of Helminthosporium maydis Race T. Mary J. Trainor, Graduate Assistant, Department of Botany and Plant Pathology, Iowa State University, Ames, IA 50011; C. A. Martinson, Associate Professor, Department of Botany and Plant Pathology, Iowa State University, Ames, IA 50011. Phytopathology 68:1049-1053. . Copyright 1978 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-68-1049.

Lesion size and lesion number per unit of inoculum were used to measure the inoculum potential of Helminthosporium maydis Race T spores produced on various media. These included potato-dextrose agar, V-8 juice agar, and a glucose-mineral salts agar amended with different concentrations of nitrogen-containing compounds or with maize leaves. Inoculum potential was affected by both nitrogen source and concentration. Spores produced on maize leaves and the maize-leaf + mineral salts agar had a higher inoculum potential than spores produced on the other media. Spores grown on media producing high inoculum potential exhibited more rapid spore germination, higher germination percentages, and greater appressorium formation than did spores grown on media of low inoculum potential. Spore size, shape, color, and number of septations were also affected by the medium.

Additional keywords: maize, southern corn leaf blight.