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Ecology and Epidemiology

Effects of Maize Dwarf Mosaic Virus Infection of Corn on Inoculum Potential of Helminthosporium maydis Race O. Clauzell Stevens, Graduate research assistant, Department of Botany, Plant Pathology, and Microbiology, Auburn University, AL 36849, Present address of senior author: Department of Agricultural Sciences, Tuskegee Institute, AL 36088; Robert T. Gudauskas, professor, Department of Botany, Plant Pathology, and Microbiology, Auburn University, AL 36849. Phytopathology 73:439-441. Accepted for publication 18 September 1982. Copyright 1983 The American Phytopathological Society. DOI: 10.1094/Phyto-73-439.

Conidia of Helminthosporium maydis race O produced in lesions on maize dwarf mosaic virus (MDMV)-infected corn leaves were compared with those produced on MDMV-free leaves and artificial media. Sporulation began sooner and was more abundant in lesions on MDMV-infected leaves. Conidia from these lesions were 24- 87% longer, contained two to four more septa, showed higher rates of germination and appressorium formation, and incited more and larger lesions than did conidia produced on MDMV-free leaves, xylose or glucose media, or potato-dextrose agar. The increased inoculum potential associated with the increased size of conidia suggests there was increased energy available in the conidia for germination and infection. Enhancement of conidial size appeared to be related to increased leakage in MDMV-infected leaves, which led to increased availability of nutrients for growth and sporulation of H. maydis.