VIEW ARTICLE

Interaction of Genes for Pathogenicity and Virulence in Trichometasphaeria turcica with Different Numbers of Genes for Vertical Resistance in Zea mays. R. R. Nelson, Professor, Department of Plant Pathology, The Pennsylvania State University, University Park 16802; D. R. MacKenzie(2), and G. L. Scheifele(3). (2)(3)Research Assistants, respectively, Department of Plant Pathology, The Pennsylvania State University, University Park 16802. Phytopathology 60:1250-1254. Accepted for publication 21 March 1970. DOI: 10.1094/Phyto-60-1250.

Differences in pathogenicity and virulence among isolates of Trichometasphaeria turcica (Helminthosporium turcicum) to maize were demonstrated by comparing qualitative and quantitative capacities to cause disease on four inbred lines of maize differing in number of chromosome arms with genes for vertical resistance. The increased virulence of isolates with more genes for pathogenicity suggests that virulence is conditioned both independently of and in part by genes for pathogenicity. The results indicate that genes for vertical resistance not only govern qualitative resistance to some isolates, but also quantitatively condition the amount of disease.