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Resistance

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.