Plant & Animal Genome IX Conference

Poster: Large Insert Libraries, Gene Isolation, Etc.
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PROGRESS IN CLONING BARLEY rpg4 GENE

¹ Department of Crop and Soil Sciences, Washington State University, Pullman, WA 99164, USA

² Department of Plant Pathology, North Dakota State University, P.O. Box 5012, Fargo, ND 581055012, USA

³ Department of Crop and Soil Sciences and School of Molecular Biosciences, Washington State University, Pullman, WA 99164, USA

The rpg4 locus confers resistance to the barley stem rust fungus Puccinia graminis pathotype QCC. It was physically and genetically localized on two overlapping BAC clones covering an estimated 300-kb region of the long arm of barley chromosome 7(5H) (Druka et al MGG in press). We have increased our mapping population size to 5200 gametes which allowed to position rpg4 proximal to CDO419, on the proximal two-thirds of the 160 kb barley BAC clone 259B20. CDO419 is an oat cDNA probe encoding the heat shock protein, Hsp70. It was suggested as a candidate gene for rpg4 based on mapping in 1775 gametes (Druka et al PAG-VIII). Precise positioning of rpg4 in respect to proximal markers in 5200 gametes will be repeated due to ambiguous phenotyping results of two recombinant lines. Of particular interest is line SQ102, progeny of which has segregating rpg4 phenotype. SQ102 is doubled haploid, which so far has not displayed any genotypic evidence of heterozygosity. The rpg4 barley BAC contig is being extended to cover the possibility of a more proximal location of the gene. We are sequencing 259B20 BAC clone. Analysis of the preliminary sequence of this BAC clone in respect to genetic mapping of rpg4 and comparison with rice sequence when it becomes available will be presented.