Molecular mapping of the Rph7.g leaf rust resistance gene in barley (Hordeum vulgare L.)

In many temperate areas of the world, leaf rust is becoming an important di sease of barley. In the last decade, new races of Puccinia hordei G. Otth h ave emerged which are virulent against the so-far most-effective race-speci fic resistance genes, such as Rph7. Marker-assisted selection greatly facil itates the pyramidization of two or more resistance genes in a single varie ty in order to achieve a more comprehensive resistance. Such a strategy req uires the development of efficient and reliable markers. Here, we have deve loped a linkage map and found RFLP markers closely linked to the Rph7.g res istance gene on chromosome 3HS of barley. The receptor-like kinase gene Hv3 Lrk that maps at 3.2 cM from Rph7.g was used to develop a PCR-based marker by exploiting a single nucleotide polymorphism. This marker was detected in 11 out of 12 (92%) barley lines having Rph7 and represents a valuable tool for marker-assisted selection. In addition, the identification of markers flanking Rph7.g provides the basis for positional cloning of this gene.