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Comparison of Near-Isogenic Maize Lines With and Without the Ht1 Gene for Resistance to Four Foliar Pathogens. S. Leath, Department of Plant Pathology, University of Illinois, Urbana 61801; W. L. Pedersen, Department of Plant Pathology, University of Illinois, Urbana 61801. Phytopathology 76:108-111. Accepted for publication 26 July 1985. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/Phyto-76-108.

Greenhouse studies were conducted to evaluate the effect of the Ht1 gene in conferring resistance to four foliar pathogens of maize (Zea mays). First, inbreds Va26, B84, and A634 were used to determine differences among near-isogenic lines. Both resistant and susceptible plants selfed once from backcross (BC) programs were compared with each other and their recurrent parents for resistance to E. turcicum race 2. The Ht1 version of Va26 (BCHt1) had fewer and smaller lesions than its recurrent parent. Other plants selfed out of the backcross program carried the recessive allele at the Ht1 locus (BCht1); these plants had the same size lesions as their recurrent parent and lesions were larger than the lesions on BCHt1 plants. The BCHt1 plants from B84 had shorter incubation periods than those of the recurrent parent or BCht1 plants. No differences were detected with inbred A634. Second, a series of six maize hybrids either homozygous dominant or recessive for the Ht1 gene were inoculated separately with three foliar pathogens: Bipolaris maydis, Helminthosporum carbonum, and Colletotrichum graminicola. Hybrids B73Ht1 x MS71 and A632Ht1 x A619Ht1 infected with B. maydis had larger lesions than their near-isogenic ht1 counterparts. When infected with H. carbonum race 3, H100 x Mo17Ht1 had larger lesions than H100 x Mo17; however, A619Ht1 x A632Ht1 had smaller lesions than A619 x A632. No differences within hybrid pairs were detected with Colletotrichum graminicola.