Development Of Molecular Markers Linked To The Resistance Gene YrSp Against Wheat Stripe Rust

Wheat stripe rust (Puccinia striiformis Westend. f. sp. tritici) is common and serious in China. Growing resistant cultivars is the most economic, effective and environment-friendly way to control the disease. "Breakdown" of resistance of cultivars has become a noticeable problem in control of wheat stripe rust because of high variability of the pathogen and simplification of resistance gene in commercial cultivars. Spaldings Prolific is one of the wheat stripe rust differential cultivars used in Europe. The resistance gene YrSp in Spaldings Prolific shows good resistance to most races of wheat stripe rust prevalent in China and has not been used in wheat breeding. Development of molecular markers linked to YrSp gene will promote utilization of the resistance gene, accelerate breeding process and be helpful to pyramiding of resistance genes in wheat breeding.In this study, AFLP markers for YrSp gene were identified and SCAR markers were developed using the near-isogenic line (NIL) YrSp/6 x Avocet S and its susceptible parent Avocet S as materials with the YrSp gene donor parent Spaldings Prolific as control. The main results were given as follows:1. A total of 225 primer combinations were used in AFLP analysis of the materials YrSp/6×Avocet S, Avocet S and Spaldings Prolific. Twelve polymorphic DNA fragments were found reproducible. Preliminary genetic linkage test showed that 6 bands (P34M54₄₂₁, P70M62₁₇₁, P7OM62₁₇₀, P32M59₂₀₈, P32M59₁₆₃, P36M53₁₆₄). respectively amplified by 4 primer combinations, were linked to the YrSp gene.2. The polymorphic DNA fragments P34M54₄₂₁ P70M62₁₇₁,P70M62₁₇₀, P32M59₂₀₈, P32M59₁₆₃, P36M53₁₆₄ were recovered from gel and cloned in pGEM?-T Easy vector, then sequenced from two ends. According to the sequences, two pairs of specific primers were designed and synthesized. Three of them (P34M54₄₂₁, P32M59₂₀₈, P36M53₁₆₄) were successfully converted into SCAR markers, i. e. SC-P34M54₃₇₈, SC-P32M59₁₄₇ and SC-P36M53₉₉.3. The genetic relationship between the 3 SCAR markers and SSR marker (Xwmc441) were test with 208 segregating F₂ plants derived from a cross between Avocet S and the NIL YrSp/6xAvocet S. Genetic distances and relationship between the markers and the target gene were calculated by the software MAPMAKER 3.0b. Genetic linkage map was drawn and the 4 markers were located on one side of the YrSp gene. The marker SC-P34M54₃₇₈ was closest to the YrSp gene (2.9 cM), the other 3 markers were successively SC-P32M59₁₄₇ (3.8cM), SC-P36M53₉₉ (3.8 cM) and Xwmc441 (18.6 cM).