Validating molecular markers for barley leaf rust resistance genes Rph5 and Rph7

Leaf rust, caused by Puccinia hordei, is a serious threat to barley (Hordeum vulgare L.) production. Genes Rph5 and Rph7 confer resistance to many of the most prevalent races of P. hordei in the United States and Europe, respectively. The reliability and diagnostic capabilities of several molecular markers for these two genes were evaluated and validated for use in gene postulation, marker-assisted selection (MAS) and eventual pyramiding of genes Rph5 and Rph7 with other effective resistance genes. Fifty-eight winter barley experimental lines developed at Virginia Polytechnic Institute and State University, as well as seven barley cultivars were phenotyped for reaction to three diverse isolates of P. hordei and genotyped with molecular makers closely linked to genes Rph5 and Rph7. Sequence tagged site markers TC2863-12.4 and ABG70 as well as simple sequence repeat marker AY642926-CA11 were reliable and diagnostic in gene postulation and have potential for use in MAS and pyramiding of genes Rph5 and Rph7. Comparison of phenotypic and genotypic data revealed that one barley line VA04H-95 has genes Rph5 and Rph7 and at least one unknown gene.