Plant & Animal Genomes XI Conference

January 11-15, 2003
Town & Country Convention Center
San Diego, CA

Poster: Gene Isolation
            

IDENTIFICATION AND ANALYSIS OF CANDIDATE GENES FOR THE BARLEY AND RYE STEM RUST RESISTANCE GENES rpg4 AND RpgQ

¹ Scottish Crop Research Institute, Invergowrie, Dundee DD2 5DA, Scotland, UK

² Department of Crop and Soil Sciences, Washington State University, Pullman, WA 99164, USA

³ Arizona Genomics Institute, University of Arizona, 303 Forbes Building, Tucson, AZ 85721, USA

⁴ Department of Plant Pathology, University of Minnesota, 495 Borlaug Hall, St. Paul, MN 55108, USA

⁵ School of Molecular Biosciences, Washington State University, Pullman, WA 99164, USA

All currently grown commercial barley cultivars in the US Midwest are susceptible to Puccinia graminis f. sp. tritici pathotype QCC. The barley line Q21861 is highly resistant to pathotype QCC due to a temperature sensitive gene, rpg4, and to the rye stem rust pathogen Puccinia graminis f. sp. secalis due to another gene designated RpgQ. The rye stem rust resistance gene RpgQ is temperature sensitive like rpg4, but confers dominant resistance and appears to be very closely linked to rpg4. We constructed ca 0.4 Mb barley BAC contig and ultra-high resolution genetic linkage map across rpg4 and RpgQ genes. Precise positioning of both genes on the genetic map was difficult therefore we have searched for possible candidate genes by partial sequencing of overlapping BAC clones covering the region. Sequence analysis of one BAC clone revealed the presence of a possible candidate ORF, encoding a putative protein with homology to phosphoinositol transfer proteins. SNP analysis of this ORF from susceptible and resistant barley cultivars did not reveal clear phenotypic association. Partial sequence analysis of two other BAC clones distal to ARD2065 identified several different ORFs, two of them with homology to known plant disease resistance genes. These resistance gene analog clusters are closely linked and may represent the rpg4 and RpgQ resistance genes. Detailed structural analysis and possible association with the stem rust disease resistance genes will be presented.