Physical Mapping of the Barley rpg4 Locus.

Arnis Druka 1, David A. Kudrna 1, Feng Han1,3, Brian J. Steffenson4, and Andris Kleinhofs1,2
1. Dept. of Crop and Soil Science, Washington State University, Pullman WA 99164
2. Dept. of Genetics and Cell Biology, Washington State University, Pullman WA 99164
3. Pioneer Hi-Bred International, Inc. 7300 NW 62nd Ave, Jonston IA 50131 (present address)
4. Dept. of Plant Pathology, North Dakota State Univ., Fargo ND 58105

The rpg4 locus confers resistance to the barley stem rust fungus Puccinia graminis pathotype QCC. Genetic mapping showed that rpg4 is located in the sub-telomeric region of barley chromosome 7L between the distal RFLP markers ABG391 and R273, 1.6 and 0.8 cM from rpg4, respectively and the proximal RFLP marker Aga5 which is about 1.8 cM from rpg4. The physical/genetic distance in the rpg4 region has been estimated at 200 kb/cM (Kunzel and Korzun, in V Int. Oat and VII Int. Barley Symposium, Vol.2 pp 197-206, '96). Thus, the predicted physical distance between Aga5 and R273 is about 520 kb. Using a 6X barley cv. Morex BAC library, we identified new RFLP markers from two overlapping BAC clones covering the rpg4 locus. The closest markers map about 0.2 cM apart. The physical contig data suggest that they are less than 200 kb apart.

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