Plant & Animal Genome VI Conference

P32

IS THERE A BARLEY STEM RUST RESISTANCE GENE Rpg1 HOMOLOG IN RICE?

1. Departments of Crop and Soil Sciences and Genetics and Cell Biology, Washington State University, Pullman, WA 99164, USA
2. Center for the Application of Molecular Biology to International Agriculture, GPO Box 3200, Camberra, ACT 2601, Australia
3. Department of Plant Pathology, North Dakota State University, Fargo, ND 58105, USA

Barley stem rust, caused by the fungus Puccinia graminis f. sp. tritici, is conferred by a single resistance gene Rpg1. Genetic mapping located the Rpg1 to the telomeric region of barley chromosome 1S. Map-based cloning of the Rpg1 is being carried out using rice as an intergenomic cloning vehicle. A rice BAC clone covering the Rpg1 region was identified. A detailed physical map and plasmid contig was established for the rice BAC fragment containing the Rpg1 flanking markers pM13 and B24. This fragment covers a rice DNA physical distance of ca. 90 kb and a barley genetic distance of 0.6 cM based on 1400 segregating gametes. Further high resolution mapping with 3000 gametes yielded a 20 kb rice fragment containing the Rpg1 flanking markers B172 and SX3L1.2. Complete sequencing of this 20 kb fragment resulted in the identification of an open reading frame coding for a putative membrane protein, a potential candidate for Rpg1. However, this membrane protein did not show homology with published plant disease resistance genes. Experiments to determine the probable function of this gene are in progress.