Fine Mapping Of The Major QTL QYm.nau-2D In Resistance To Wheat Yellow Mosaic Virus

Wheat yellow mosaic (WYM), caused by wheat yellow mosaic movirus (WYMV), was a soil-borne bymovirus diseases and caused wheat yield loss at 10%-30% in general and may be up to 70% in severe epidemic years. In China, WYM has spread to many provinces along the Yangtze River and Huai River regions, and has become one of the most serious diseases threaten wheat production. Traditional agricultural control practices, such as application of chemical fungicides and crops rotation, is not effective for WYMV control. Identification of new resistance genes, the development and utilization of resistance varieties is the best choice for WYM control.Using a RILs population derived from ’Yining wheat’ and ’Zhen9523’, a major QTL QYm.njau-2D on chromosome 2DL which was associated with resistance to WYM and could explain 85.73% phenotypic variance, was ideatified. In order to fine map QYm.njau-2D, a secondary F2 population derived from ’RIL11-14’, a highly WYMV-resistant RIL in which only the major QTL QYm.njau-2D was included, and ’Zhen9523’, was used to map QYm.nau-2D to an interval between co-dominant markers Xcfd267 and 2EST811 which covered a genetic region of 0.7cM, with their genetic distances 0.4cM and 0.3cM, respectively.In this study, by further saturate the target region, new molecular markers developed. We also construct a new mapping population with the long term goal to clone the QYm.nau-2D. The main results obtained were as follows:1. Increasing the marker density for QYm. nau-2DMolecular markers development:(1) EST markers:DNA sequence for two markers 2EST811 and Wxe1338 flanking QYm.nau-2D were used to identify the collinear regions in the genomes of Brachpodium. The collinear genomic sequence was used as queries for a BLASTn search to identify wheat ESTs most likely near QYm.nau-2D.2 out of 34 primer pairs designed from wheat ESTs detected polymorphisms between two parents and the marker 2EST898 could be mapped in the’Yining wheat’/’Zhen9523’RIL population. (2) SSR markers:with the marker 2EST811, we also found collear region in wheat D genome. 151 randemly selected scaffolds were used to design SSR parimer pairs. However, no parimer pairs detected polymorphism between’Yining Wheat’and’Zhen 9523’.2. Fine mapping of QYm.njau-2D using a secondary F2population from ’RIL11-14’ and’Zhen 9523’In order to fine map the QYm.nau-2D, a secondary F2 population consisting of 1320 plants were constructed by crossing ’RIL11-14’ and ’Zhen9523’(Guo,2011). In this study, in addition to the residual heterozygous plants from F2:3 population, we expanded the population to 4659 plants in which 1320 were susceptible and 3339 were resistant. Two flanking markers for QYm.nau-2D, Xwmc41 and Xwmc181, were used to screen 100 recombinants. The other 7 linked markers for QYm.nau-2D (2EST777,2EST730, WXE1339, WXE368,2EST811, WXE1338 and 2EST898) were used to further screen 46,44,41,41,41, 15 and 36 recombinants, respectively, in the above 100 recombinants. QYm.nau-2D flanked by WXE1339 (or WXE368、or 2EST811) and WXE1338 were confirmed which was consistent with the result by Guo (2011) using the secondary F2 population.3. The construction of F2 population from Triticum aestivum cv Chinesespring-Aegilops tauschii 2D substitution line ’2011I-P78’ and ’Yining wheat’ The T. aestivum cv Chinesespring-Ae. tauschii 2D substitution line ’2011I-P78 showed high susceptibility to WYM. A F2 population consisting of 1484 plants were constructed by crossing’2011I-P78’with’Yining wheat’.24 out of 271 above SSR primer pairs detected polymorphism between the two parents and 12 polymorphic markers could be mapped in the new population and were linked to QYm.nau-2D.