SCAR Molecular Markers For Leaf Rust Resistance Gene Lr42 In Wheat

Leaf rust caused by Puccinia triticinia is one of the most devastating foliar diseases on wheat. Major leaf rust resistance gene Lr42 is transferred to common wheat line KS91WGRC11 (=Century*3/T. tauschii TA2450, T. tauschii TA2450). It shows strang leaf rust resistance to Puccinia triticina in China. The identification of molecular markers linked to rust resistance genes facilitates marker assisted selection (MAS) and gene pyramiding in breeding programs. However, molecular marker linked to Lr42 gene only has been reported on its SSR markers. There is a need to find complete linkage or tightly linkage markers of Lr42 in wheat.Random amplification polymorphism DNA (RAPD) markers were screened using Thatcher, near-isogenic lines carrying Lr15 resistance gene against leaf rust, F2 progeny population coming from KS91WGRC11 and Thatcher. The results showed that most of the 800 random primers screened for RAPD analysis provided clear amplification products. 163 of them amplified polymorphic bands in KS91WGRC11 and 2 wheat leaf rust resistance NILs, with about 20.4%. Further analysis of 202 F₂ progeny population of KS91WGRC11xThatcher was carried out using 163 primers. Five primers displayed polymorphisms between the resistant and susceptible plants. Linkage analysis through MAPMAKER 3.0b software showed that the primer S1012 was tightly linked to Lr42 with 2.9cM. The specific DNA fragment was reclaimed, cloned and sequenced. Specific sequence character amplified region (SCAR) primers were designed according to the sequence. Three pair of primers were obtained which displayed specific betweent the resistance and suscuptible F₂ population, and named as SCS1020₁₀₀₆, SCS1020₁₂₉₅ SCS1020₉₀₃ respectively. The stable SCAR markers for the Lr42 resistance gene provided a convenient and reliable identification of molecular marker assisted in its progeny population screening.