Genetic analysis of durable resistance to yellow rust in bread wheat

Yellow rust, caused by Puccinia striiformis, is one of the most damaging diseases affecting bread wheat in temperate regions. Although resistance to yellow rust is frequently overcome by new virulent races, a durable form of resistance in the French bread wheat Camp Remy (CR) has remained effective since its introduction in 1980. We used 217 F7 recombinant inbred lines (RILs) derived from the cross between CR and the susceptible cultivar Recital to identify and map quantitative trait loci (QTLs) involved in durable yellow rust resistance. Six significant QTLs that were stable over a 4-year period were detected. Two QTLs, denoted QYr. inra-2DS and QYr. inra-5BL. 2, were located on the short arm of chromosome 2D and the long arm of chromosome 5B, respectively. Each explained on average 25 - 35% of the observed phenotypic variation and were probably inherited from Cappelle Desprez, a parent of CR that confers durable adult plant resistance to yellow rust. QYr. inra-2DS probably corresponds to the Yr16 gene. The most consistent QTL, designated QYr. inra-2BL, was located on the centromeric region of chromosome 2B and explained 61% of the phenotypic variation in 2003. This QTL was responsible for seedling-stage resistance and may correspond to a cluster of genes, including Yr7. The remaining QTLs were mapped to the short arm of chromosome 2B (R-2 = 22 - 70%) and to the long arm of chromosomes 2A ( R-2 = 0.20 - 0.40) and 5B (R-2 = 0.18 - 0.26). This specific combination of seedling and adult plant resistance genes found in CR and CD may constitute the key to their durable resistance against yellow rust.