Phenotypic Rating of Maize Dwarf Mosaic Virus Infection of Sweet Corn (Zea mays saccharata).

Sweet corn production is an economically important industry in the Upper Midwest with both Wisconsin and Minnesota being among the top three sweet corn producing states in the United States. A major pest of sweet corn is Maize Dwarf Mosaic Virus (MDMV), an aphid-transmitted potyvirus, which causes chlorotic streaks on foliage.  MDMV also halts ear formation and development and causes stunted growth.  MDMV can cause up to a forty percent yield loss. Breeding MDMV resistant hybrid corn varieties is very important for the future of the sweet corn industry in Wisconsin.  Selection for MDMV resistance is based on a phenotypic rating scale that assesses disease severity and percent of infected plants within a given row. The objectives of this research are to 1) determine the relationship between MDMV virus incidence and dates of silking and tasseling and 2) determine the relationship between MDMV virus inoculations and genotype and 3) to determine if three inoculations result in more symptomatic plants than two inoculations. Determining the effect of MDMV on silk and tassel date will have a direct effect on breeding procedures and help farmers produce a better quality, disease resistant crop. Additionally, acquiring resistant genotypes will further help breeders select for MDMV resistant plants for the future of sweet corn production.