| Wheat yellow mosaic (WYM), which caused by wheat yellow mosaic bymovirus (WYMV) is a soil-borne bymovirus disease, is an important disease in the winter wheat growing regions and it has growing as one of the most serious diseases in wheat production of China. The mining of more resistance gene resources is of critical importance in wheat breeding for WYMV resistance.The wheat variety,’Xifeng Wheat’, originally introduced from Japan into China, possesses many elite characters such as resistances to powdery mildew, fusarium head blight, stripe rust, WYMV as well as resistances to lodging and pre-harvest sprouting. Several new wheat varieties with high level of resistance to WYMV have been released using’Xifeng Wheat’as breeding parents directly or indirectly in China (e.g.’Ningmai 9’, ’Ningmai 16’and’Yangmai 18’). The wheat variety,’Zhen 9523’, developed by Jiangsu Hilly Area Zhenjiang Agricultural Research Institute, strong stem, bigger spikes and more grains, higher grain weight, good grain quality, and has moderately resistant to fusarium head blight, leaf rust and sheath blight, but it is highly susceptible to WYMV. In the present research, a RIL population was constructed using the two varieties as parents, and a molecular marker based linkage map was established. Based on the evaluation of WYMV resistance, QTLs associated with WYMV resistance were analyzed. A secondary F2 population was constructed to fine map a major QTL QYm.nau-5A.1 identified for WYMV resistance in the RIL population, which would provide an important foundation for the map-based cloning of QYm.nau-5A.1. The major results obtained were as following:1. Identification of QTLs for WYMV resistance in the RIL populationGenetic analysis for the WYMV resistance was conducted by mixed major gene plus polygene inheritance models. Results showed that the WYMV resistance was controlled by two or three major genes plus polygenes, major genes and polygenes heritabilities were 81.00-93.93% and 5.55-17.17%, respectively. Among the 1,790 SSR, STS, EST-SSR and EST-STS markers,317 primer pairs could amplify clear and reproducible polymorphic band (s) between the two parents and the RILs. Among them, when using the JoinMap 4.0 software,271 markers representing 274 non-redundant loci assigned to the molecular marker-based linkage map contained 33 linkage groups spanning a total genetic length of 1,685.3cM with an average marker interval of 9.8cM. All the 21 wheat chromosomes were represented by at least one linkage group. Based on the molecular marker-based linkage map and phenotypic data of WYMV resistance collected from four-year, two-location replicated field trials, QTLs associated with the WYMV resistance were detected with the Windows QTL Cartographer V2.5 software by composite interval mapping (CIM) method. Three QTLs, QYm.nau-3B.1, QYm.nau-5A.1 and QYm.nau-7B.1, were detected on chromosomes 3BS,5AL and 7BS, respectively. The increased allele effects were all provided by the resistant parent’Xifeng Wheat’. Among the three QTLs, QYm.nau-3B.1 and QYm.nau-5A.1 were detected in all the four trials, and could explain 3.3-10.2% and 25.9-53.7% of the phenotypic variation, respectively, while QYm.nau-7B.1 was detected in one trial that explained 4.9% of the phenotypic variation.2. Fine mapping of the major QTL QYm.nau-5A.1In order to fine map the QYm.nau-5A.1, based on QTL analysis for WYMV resistance, a secondary F2 population consisting 6002 plants were constructed by a cross ’RILV-6’and ’Zhen 9523’, and the highly WYMV-resistant RIL’RILV-6’only contained QYm.nau-5A.1 has similar agronomic traits with’Zhen 9523’. When using the markers to screen the recombinats in all the 1340 susceptible plants, the QYm.nau-5A.1was flanked by Xwmc415.1 and 5EST-440, and the two EST-STS markers were co-separated with the QYm.nau-5A.1. Linkage analysis showed that the genetic distances were 0.0cM between Xwmc415.1,5EST-44,5EST-90 and QYm.nau-5A.1, and that the genetic distances were 0.1 cM between 5EST-440 and QYm.nau-5A.1. Finally the QYm.nau-5A.1 was flanked by the two markers Xwmc415.1 and 5EST-440 with a distance of 0.1cM, which would provide an important foundation for the map-based cloning of QYm.nau-5A.1.Three markers, Xwmc415.1,5EST-44 and 5EST-90 closely linked with QYm.nau-5A.1 identified in the present study, were used for marker analysis of the wheat varieties population consisting of 46 varieties with known WYMV resistance. Result showed that that QYm.nau-5A.1 was present in 12 varieties with WYMV-resistance, and all the 12 WYMV-susceptible varieties amplified the same specific band as in’Zhen 9523’using the three markers. So the three markers were very effective to identify the QYm.nau-5A.1 in the wheat varieties population, and they should be useful in marker-assisted selection (MAS) of WYMV resistance in wheat breeding.3. QTL analysis of the three important agronomic traits in the RIL populationGenetic analysis for plant height, spike length and spikelet number per spike were conducted by mixed major gene plus polygene inheritance models. Results showed that the three agronomic traits were all controlled by two major genes plus polygenes.Based on the molecular marker-based linkage map and phenotypic data of the three agronomic traits collected from two-year, one-location replicated field trials, QTLs associated with the three traits were detected with the Windows QTL Cartographer V2.5 software by CIM method. Four QTLs for the plant height, QPh.nau-2D, QPh.nau-3B.1, QPh.nau-4B and QPh.nau-4D, were detected on chromosomes 2DS,3BL,4BL and 4DS, respectively. Among them, QPh.nau-2D, QPh.nau-4B and QPh.nau-4D were all detected in all the two trials and could explain 7.4-7.9%,28.3-35.6% and 29.3-30.3% of the phenotypic variation, respectively. Five QTLs for the spike length, QSl.nau-2D.a, QSl.nau-2D.b, QSl.nau-5A.1, QSl.nau-5B and QSl.nau-6B, were detected on chromosomes 2DS,2DS, 5AL,5BS and 6BL, respectively. Among them, QSl.nau-2D.a, QSl.nau-2D.b and QSl.nau-5A.1 were detected in all the two trials and could explain 20.6-29.0%,5.0% and 8.8-11.6% of the phenotypic variation, respectively. Five QTLs for the spikelet number per spike, QSn.nau-1A.1, QSn.nau-5A.1.a, QSn.nau-5A.1.b, QSn.nau-5D and QSn.nau-6B, were detected on chromosomes 1AS,5AL,5AL,5DL and 6BL, respectively. Among them, QSn.nau-1A.1 and QSn.nau-5D were detected in all the two trials and could explain 10.2-11.1% and 7.8-11.9% of the phenotypic variation, respectively. |
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