BARLEY HOMOLOGUES OF THE MAIZE RP1 GENE DO NOT CO-SEGREGATE WITH THE RPG1 LOCUS

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

² Department of Genetics and Cell Biology, Washington State University, Pullman, WA 99164 USA

³ Department of Plant Pathology, North Dakota State University, P.O. Box 5012, Fargo, ND 58105-5012 USA

⁴ Dept.Plant Pathology, Washington State Univ. Pullman, WA 99164-6430 USA

The barley Rpg1 gene has conferred durable resistance to most but not all races of wheat stem rust (Puccinia graminis Pers.:Pers. f.sp. tritici Eriks & E. Henn.)for the last half century. High resolution mapping located Rpg1 close to the telomere on barley chromosome 1(7H) flanked by rice RFLP markers B172 and S1558. The maize PIC20 probe, encoding part of the maize Rp1 NBS/LRR disease resistance gene provided by Dr. T. Pryor, was used as a probe to screen a 6.3X barley BAC library. Sixty- six BACs were selected and classified into 11 (A-K) groups based on the fragment size hybridizing to PIC20. Five of these groups A,B,C,D,F) form a contig of approximately 400 kb that overlaps with the rice marker S1558 and extends 0.2 cM proximal to Rpg1, but none co-segregated with Rpg1 in 3,000 gamete segregating populations phenotyped with the stem rust pathotype MCC. The H,I,J,K group members mapped to a single chromosome 5(1H) locus while the E group mapped to chromosome 3(3H). The G group has not been precisely located, but it does not map to the Rpg1 region. All fragments hybridizing with PIC20 were subcloned and sequenced. Sequence analysis and comparisons will be presented.