Interactions Between Maize Streak Virus and Downy Mildew Fungi in Susceptible Maize Cultivars. Vernon D. Damsteegt, U.S. Department of Agriculture, Agricultural Research Service, Foreign Disease-Weed Science Research Unit, Frederick, MD 21702. M. R. Bonde, and A. D. Hewings. U.S. Department of Agriculture, Agricultural Research Service, Foreign Disease-Weed Science Research Unit, Frederick, MD 21702; and USDA-ARS, Crop Protection Research Unit, Dept. of Plant Pathology, University of Illinois, 1102 South Goodwin Avenue, Urbana 61801. Plant Dis. 77:390-392. Accepted for publication 1 December 1992. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1993. DOI: 10.1094/PD-77-0390.

The effects of systemic infection by Peronosclerospora philippinensis and P. sorghi (both downy mildew fungi) and maize streak virus (MSV) on host reaction and pathogen reproduction were quantified in two maize cultivars. The maize cultivars tested (DeKalb XL 43A and Pioneer 3369A) were susceptible to all pathogens. Infection by MSV masked symptoms of downy mildew infection. Reduction in height and biomass were significantly greater with pathogen combinations than with single pathogens. Systemic infection by either downy mildew fungus had no effect on MSV titer. Infection by MSV reduced plant biomass, leaf area, and total sporulation of either fungus; however, sporulation per unit leaf area was not affected.

Keyword(s): Cicadulina mbila, synergism.