Development Of Barley Introgression Lines Carrying The Leaf Rust Resistance Genes Rph1 To Rph15

Abstract

Barley (Hordeum vulgare) is the fourth most planted and harvested grain crop in the world. In many production areas, barley is attacked by the leaf rust pathogen (Puccinia hordei), a basidiomycetous fungus that reduces both its yield and quality. Many leaf rust resistance genes, known as reaction to P. hordei (Rph) genes, have been described in barley. Resistance deployed in cultivars has often been transient due to the pertinacious nature of single gene virulence mutations in P. hodei populations. To differentiate genetic variants for virulence in P. hordei populations, plant pathologists use barley accessions with different resistance genes, referred to as a differential set. The barley leaf rust differential set evolved through time as more Rph genes were described. The sources of Rph1-15 were derived from barleys with diverse geographic origins and agro-morphological traits. Ideal differential sets include lines where single resistance genes are backcrossed into the genetic background of an adapted susceptible cultivar. Sources for Rph1-15, along with many other Rph gene donors were backcrossed to the susceptible cultivar Bowman. Overall, 95 Bowman introgression lines for leaf rust resistance were developed, and a single line was recommended for use as the new backcrossed differential host line for each individual Rph1-15 gene. Genomic positions and gene candidates for Rph1-15 were characterized and the existence of possible new resistance genes was postulated. The new Bowman Rph1-15 differential lines will facilitate the efficient virulence phenotyping of P. hordei and serve as valuable genetic stocks for Rph gene stacking and cloning in barley.