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

Pyrenophora graminea is the seed-bornepathogen causal agent of barley leaf stripe disease. Nearisogeniclines (NILs) carrying resistance of the cv “Thibaut”against the highly virulent isolate Dg2 were obtainedby introgressing the resistance into the geneticbackground of the susceptible cv “Mirco”. The segregationof the resistance gene was followed in a F2 populationof 128 plants as well as on the F3 lines derived fromthe F2 plants; the segregation fitted the 1:2:1 ratio for asingle gene. By using NILs, a RAPD marker associatedwith the resistance gene was identified; sequence-specific(STS) primers were designed on the basis of the ampliconsequence and a RILs mapping population with anAFLP-based map were used to position this molecularmarker to barley chromosome 1 S (7HS). STS and CAPSmarkers were developed from RFLPs mapped to thetelomeric region of barley chromosome 7HS and threepolymorphic PCR-based markers were developed. Thesegregation of these markers was followed in the F2 populationand their map position with respect to the resistancegene was determined. Our results indicate that theThibaut resistance gene, which we designated as Rdg2a,maps to the telomeric region of barley chromosome 7HSand is flanked by the markers OPQ-9700 and MWG 2018at distances of 3.1 and 2.5 cM respectively. The suitabilityof the PCR-based marker MWG2018 in selectionassistedbarley breeding programs is discussed.