Identification and mapping of a new leaf stripe resistance gene in barley (Hordeum vulgare L.)

Pyrenophora graminea is the seed-borne pathogen causal agent of barley leaf stripe disease. Near-isogenic lines (NILs) carrying resistance of the cv " Thibaut" against the highly virulent isolate Dg2 were obtained by introgres sing the resistance into the genetic background of the susceptible cv "Mirc o". The segregation of the resistance gene was followed in a F-2 population of 128 plants as well as on the F-3 lines derived from the F-2 plants; the segregation fitted the 1:2:1 ratio for a single gene. By using NILs, a RAP D marker associated with the resistance gene was identified; sequence-speci fic (STS) primers were designed on the basis of the amplicon sequence and a RILs mapping population with an AFLP-based map were used to position this molecular marker to barley chromosome 1 S (7HS). STS and CAPS markers were developed from RFLPs mapped to the telomeric region of barley chromosome 7H S and three polymorphic PCR-based markers were developed. The segregation o f these markers was followed in the F-2 population and their map position w ith respect to the resistance gene was determined. Our results indicate tha t the Thibaut resistance gene, which we designated as Rdg2a, maps to the te lomeric region of barley chromosome 7HS and is flanked by the markers OPQ-9 (700) and MWG 2018 at distances of 3.1 and 3.5 cM respectively. The suitabi lity of the PCR-based marker MWG2018 in selection-assisted barley breeding programs is discussed.