Genetic Analysis And Molecular Mapping Of Leaf Rust Resistance Gene(s) In Romania Wheat Line Fundulea 900

Wheat leaf rust, caused by Puccinia triticina, is one of the most important and widespread diseases in wheat. It is adapted to a wide range of climates, occurs wherever wheat is grown, and given favorable conditions, the disease can cause yield losses of up to 40%. In China, leaf rust occurs serious in North and Northeast regions, particularly in Southwest and Yangtze River Valleys. The disease also occurs in many wheat production regions in the world, such as North America, Europe, Asia, Australia and Africa, and it caused destructive yield losses of wheat. With global warming, climatic conditions will become more favorable for the occurrence and spread of leaf rust. Resistant cultivars are the most efficient, economic and environmentally-friendly way for reducing the losses caused by the disease. The wheat cultivars always lost their resistance to leaf rust when virulent races emerge or increase. Genetic resistance to leaf rust can be most fully utilized by information about the identity of resistance genes in current leading resistance resources and newly released cultivars. It is, therefore, very important for wheat resistance breeding and disease control to search for genetic law of leaf rust resistance, to identify and map new leaf rust resistance genes. Romania wheat line Fundulea 900, showed high levels of resistance to leaf rust, stripe rust and powdery mildew under field conditions. It is very important to use Fundulea 900 as a resistant parent for breeding resistant cultivars to leaf rust. In this study, the leaf rust resistance gene in Fundulea 900 was tested by gene postulation, the genetic analysis, and SSR markers. The main results are as follows:1) The resistance genes in Fundulea 900 were identified by comparing the reaction of Fundulea 900 to 12 Puccinia triticina races with 17 wheat lines with known leaf rust resistance genes. The result showed that the reaction patterns of Fundulea 900 were different from the 17 known Lr resistance genes used in the test and therefore Fundulea 900 may carry one new leaf rust resistance genes.2) In the seedling test, Fundulea 900, Thatcher, and their Fl, F₂ populations and F₃ families were tested for wheat leaf rust resistance with Chinese Puccinia triticina races FHTT in greenhouse. The results showed that the leaf rust resistance in Fundulea 900 was controlled by one dominant resistance gene, temporarily designated LrFun.3) SSR molecular markers and BSA were used to test the F₂ and F₃ populations for mapping the leaf rust resistance gene in Fundulea 900. A total of 1706 pairs of SSR primers were used to test the parents and their resistant and susceptible bulks. The polymorphic SSR markers between the resistant and susceptible bulks were used for analying the F₂ and F₃ populations. Linkage analysis was conducted with the software MapManager QTXb20. Results indicated that Fundulea 900 carries a single dominant resistance gene LrFun, located on chromosome 7BL. The resistance gene LrFun was closely linked to the eight known SSR loc（iXgwm344, Xwmc70, Xwmc10, Xgwm146, Xbarc50, Xwmc273, Xbarc32 and Xbarc182）on the 7B with genetic distance ranging from 2.2 cM to 19.2 cM. The two closest flanking SSR loci were Xgwm344-7B and Xwmc70-7B with genetic distances of 2.2 cM and 4.4 cM, respectively. The two closely linked SSR marker Xgwm344 and Xwmc70 were screened on DNA bulks from each of the 90 F₃ lines, providing comparative linkage of 4.4 cM and 5.7 cM, respectively. Neither value was significantly different from the results based on F₂ plants.4) Four leaf rust resistance genes Lr14a, Lr14b, Lr68 and LrBi16 are located on chromosome 7BL. Fundulea 900 and the lines carrying Lr14a, Lr14b and LrBi16 were inoculated with 12 Puccinia triticina races in a seedling test. The result showed that reaction pattern of LrFun to the races was different from those of lines with Lr14a and Lr14b. In addition, Lr68 is a adult plant resistance gene, while LrFun is a seeding resistance gene, it is definitely different from LrFun. The distances between LrBi16 and LrFun are very close, so the relationship between LrBi16 and LrFun was unclear and should be tested in the future.