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Molecular Mapping of the Crown Rust Resistance Gene Rpc1 in Barley

First author: Department of Plant Pathology, North Dakota State University (NDSU), and U.S. Department of Agriculture-Agricultural Research Service (USDA-ARS), P.O. Box 5677, Fargo, ND 58105; second author: USDA-ARS, NCSL, P.O. Box 5677, SU Station, Fargo, ND 58105; third author: Department of Plant Sciences, NDSU; fourth author: USDA-ARS, Cereal Disease Lab, St. Paul, MN 55108; and fifth author: Department of Plant Pathology, University of Minnesota, St. Paul 55108

Crown rust of barley, caused by Puccinia coronata var. hordei, occurs sporadically and sometimes may cause yield and quality reductions in the Great Plains region of the United States and Canada. The incompletely dominant resistance allele Rpc1 confers resistance to P. coronata in barley. Two generations, F₂ and F_2:3, developed from a cross between the resistant line Hor2596 (CIho 1243) and the susceptible line Bowman (PI 483237), were used in this study. Bulked segregant analysis combined with random amplified polymorphic DNA (RAPD) primers were used to identify molecular markers linked to Rpc1. DNA genotypes produced by 500 RAPD primers, 200 microsatellites (SSRs), and 71 restriction fragment length polymorphism (RFLP) probes were applied to map Rpc1. Of these, 15 RAPD primers identified polymorphisms between resistant and susceptible bulks, and 62 SSR markers and 32 RFLP markers identified polymorphisms between the resistant and susceptible parents. The polymorphic markers were applied to 97 F₂ individuals and F_2:3 families. These markers identified 112 polymorphisms and were used for primary linkage mapping to Rpc1 using Map Manager QT. Two RFLP and five SSR markers spanning the centromere on chromosome 3H and one RAPD marker (OPO08-700) were linked with Rpc1 and, thus, used to construct a 30-centimorgan (cM) linkage map containing the Rpc1 locus. The genetic distance between Rpc1 and the closest marker, RAPD OPO08-700, was 2.5 cM. The linked markers will be useful for incorporating this crown rust resistance gene into barley breeding lines.