VIEW ARTICLE

Ecology and Epidemiology

Relation of Maize Dwarf Mosaic Virus Infection to Increased Susceptibility of Corn to Helminthosporium maydis Race O. Clauzell Stevens, Graduate research assistant, Department of Botany, Plant Pathology, and Microbiology, Auburn University, Auburn, AL 36849, Present address of senior author: Department of Agricultural Sciences, Tuskegee Institute, Tuskegee, AL 36088; Robert T. Gudauskas, professor, Department of Botany, Plant Pathology, and Microbiology, Auburn University, Auburn, AL 36849. Phytopathology 72:1500-1502. Accepted for publication 17 May 1982. Copyright 1982 The American Phytopathological Society. DOI: 10.1094/Phyto-72-1500.

Helminthosporium maydis race O produced greater numbers of lesions and larger lesions on corn seedlings infected with maize dwarf mosaic virus (MDMV) than on virus-free seedlings. Germination rates of H. maydis conidia were similar on leaves of MDMV-infected and virus-free seedlings; however, conidia on MDMV-infected leaves produced more germ tubes and more than twice the number of appressoria as conidia on virus-free leaves. Washings from MDMV-infected seedlings showed greater conductivity and higher concentrations of K⁺, Cu⁺⁺, and ninhydrin-positive substances than washings from virus-free seedlings; and, leachates from MDMV-infected leaves contained greater amounts of phenol sulfuric acid-, orcinol-, and ninhydrin-positive substances and total amino acids than leachates from virus-free leaves. Increased susceptibility of MDMV-infected corn to H. maydis appeared to be related to altered permeability of virus-infected tissues and consequent increased exudations that enhanced germ tube formation and colonization by the fungus.