Genetic Markers and Leaf Rust Resistance of the Wheat Gene Lr32

Abstract

Leaf rust (caused by Puccinia triticina Eriks.) is a worldwide and yield‐limiting disease of common wheat (Triticum aestivum L.). The gene Lr32, which confers seedling resistance to leaf rust, was previously transferred from Aegilops tauschii Coss. (RL5497‐1) to chromosome 3DS of common wheat. Without exception, Lr32 conferred resistance to 616 diverse isolates of leaf rust sampled from Canadian wheat fields over the past decade (2000 to 2009). Marker alleles specific to chromosome 3DS of RL5497 were found in Lr32 backcross lines of both Katepwa (BW196R) and Thatcher (RL6086). These introgressions from A. tauschii had no adverse effects on either agronomic performance or end use quality. A map based on 338 doubled haploid lines (DHL) from the cross of BW196R × Thatcher showed that Lr32 was slightly distal (0.6 cM) to two simple sequence repeat (SSR) loci wmc43 and barc135, which cosegregated on chromosome 3DS. A survey of the fragments amplified in wheats of diverse origin showed that both wmc43 and barc135 were cross‐applicable as markers for stacking Lr32 with other broadly effective leaf rust resistance genes.