Locations of Quantitative Trait Loci Conferring Russian Wheat Aphid Resistance in Barley Germplasm STARS‐9301B

Russian wheat aphid (RWA, Diuraphis noxia Kurdjumov) infestations reduce grain yield and quality and have caused more than $1 billion in losses for barley ( Hordeum vulgare L.) and wheat ( Triticum aestivum L.) in the western United States since 1986. Our objective was to map quantitative trait loci (QTLs) conferring resistance to RWA feeding damage in the germplasm line STARS‐9301B via polymerase chain reaction–based marker assays of 191 F 2 –derived F 3 families from the cross ‘Morex’/STARS‐9301B. Morex is a susceptible six‐rowed malting barley. STARS‐9301B is a selection from RWA‐resistant Afghanistan introduction PI366450. Replicated seedling reactions to RWA infestations were used to phenotype each family based on a 1 to 9 visual rating of chlorosis. A total of 107 molecular markers was used to construct a linkage map. Quantitative trait loci analysis identified two major QTLs for resistance. The QTL on the short arm of chromosome 1H was associated with B‐hordein and explained 26% of the variation for RWA reaction. A QTL on chromosome 3H associated with EBmac0541 explained 38% of the variation. A minor QTL on chromosome 2H was associated with marker GBM1523 and explained 6% of the variation. A combined analysis indicated that the marker–QTL associations explained 59% of the phenotypic variation for RWA resistance. These markers linked with QTLs will be valuable in breeding for RWA resistance. Pyramiding the genes from STARS‐9301B with genes from other sources will be helpful for long‐term protection against RWA in barley.