Molecular Mapping of Wheat Leaf Rust Resistance Gene Lr42

Leaf rust, caused by Puccinia triticina Eriks., is an important foliar disease of Wheat (Triticum aestivum L.) worldwide. Leaf rust resistance gene Lr42 from Aegilops tauschii Coss has been used as a source of rust resistance in breeding programs. To identify molecular markers closely linked to Lr42, a segregating population, of near-isogenic lines contrasting for the presence of Lr42 was developed in the hard winter wheat cultivar Century background and evaluated for rust infection type at both seedling and adult-plant stages. Simple sequence repeat (SSR) markers were screened using bulked-segregant analysis. Two markers closely linked to Lr42 were identified on chromosome 1DS. The closest marker, Xwmc432, is about 0.8 cM from Lr42. Physical mapping of both SSR markers using Chinese Spring nullitetrasomic and ditelosomic genetic stocks confirmed that the markers lined to Lr42 were on 1DS. Markers for Lr42 were highly polymorphic between parents and among a diverse set of wheat parents and among a diverse set of wheat germplasm collected from several countries, indicating that these markers are useful for marker-assisted selection for Lr42.