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Molecular Plant Pathology

The Use of Molecular Markers to Study Setosphaeria turcica Resistance in Maize. Kevin D. Simcox, United States Department of Agriculture, Agricultural Research Service (USDA-ARS), Plant Genetics Research Unit, Columbia, MO 65211; Jeffrey L. Bennetzen, Department of Biological Sciences, Purdue University, West Lafayette, IN 47907. Phytopathology 83:1326-1330. Accepted for publication 8 September 1993. 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/Phyto-83-1326.

To facilitate understanding of the molecular basis of Htn1 resistance in maize to northern corn leaf blight, we mapped the Htn1 locus by restriction fragment length polymorphism (RFLP) analysis. Linkage with the Htn1 locus, using a backcross population, was initially detected with the RFLP probe UMC16, which hybridized to two loci: UMC16A on the long arm of chromosome three and the unmapped locus UMC16B. Independent assortment of Htn1 with UMC16A and linkage to UMC16B was verified with RFLP markers closely flanking UMC16A on the long arm of chromosome three. Information obtained from previous studies, detailing duplicate loci in maize, indicated that RFLP loci in the region around UMC16A are duplicated on the long arm of chromosome eight in the region of Idh1. RFLP loci mapping within this region on chromosome eight detected linkage with both Htn1 and UMC16B. Analysis of additional backcross progeny mapped the Htn1 locus 0.8 cM (centi-Morgans) distal to UMC117, near the recently reported location of the Ht2 locus. Segregation analysis of F₂ progeny from crosses of the inbred W22Htn1 with A619Ht2 confirmed the linkage of Htn1 with Ht2. RFLP analysis of susceptible F₂ progeny indicates that Htn1 and Ht2 are not allelic, and Ht2 maps are approximately 10 cM proximal to Htn1.