【作者】 薛树林；

【导师】 马正强；

【作者基本信息】 南京农业大学 ， 作物遗传育种， 2007， 博士

【摘要】 普通小麦是一个六倍体作物,基因组庞大且非常复杂。利用合成小麦与普通小麦杂交的重组自交系群体己构建了小麦的参考图谱（ITMI图谱）,但由于人工选择的影响以及缺乏与品种间杂交图谱的比较,ITMI图谱还不足以提供完整的小麦基因组信息。富含EST标记的遗传图谱在运用基因组信息进行作物改良方面具有重要作用。利用南大2419×望水白的品种间杂交群体,我们构建了一个区域性高密度小麦分子遗传图谱（NW图谱）。图谱总长4243.6 cM,包含891个位点,其中349个位点来自小麦EST标记。该图谱覆盖了在ITMI图谱中缺失的染色体2BS、4BL、5AS和5BL的158 cM末端区域,定位在这些区域的标记主要是EST标记。NW图谱包含31个分子标记高密度区域,其中三分之二的区域位于端粒或染色体內部区域。在这些区域中有15个具有高分辨率。我们发现低分子标记密度区域在品种间以及部分同源的亚组间表现保守。绝大多数EST标记都位于染色体的远端区域,在这些区域标记密度和重组率相对较高。小麦重要农艺性状QTLs/因主要分布于第1、2、3和5同源群染色体上,且在染色体的末端呈现出明显的成簇分布现象。尽管一般认为着丝粒区域重组率较低,但也存在例外。染色体2BL和3BS的近着丝粒区域重组率较高,近似于重组热点区。将已定位的小麦EST与水稻的BAC/PAC克隆进行比对分析,我们发现小麦的第3、6和7同源群与水稻染色体间具有更好的共线性关系。这些发现将在小麦基因组的结构和功能分析、小麦重要农艺性状基因的定位和分离以及育种实践中产生重要作用。小麦对赤霉病的抗性主要分为抗侵入性和抗扩展性。一般需要分别设置试验来定位两种类型的抗病QTL。本研究利用喷雾接种后14和21天的病小穗数(NDSD₁₄和NDSD₂₁)作为抗侵入和抗扩展的综合指标,利用两次病小穗数的差值(D_NDS)来反映抗扩展性。通过QTL定位分析,我们发现在该群体中NDS_D14和NDS_D21主要反映的是抗侵入性。利用D_NDS,我们能检测到所有的三个与抗扩展相关的主效QTLs。利用该方法,我们还发现位于染色体2B上的一个与抗扩展相关的QTL也与抗侵入相关。利用包含277个株系的南大2419×望水白群体,我们对抗侵入QTL进行了再定位.我们将4B和5A Q7L定位到更小的标记区间内,其LOD值与初级定位（136个株系）时相比有了大幅度提高。QFhi.nau-4B的LOD值由4.8增加到7.6,QFhi.nau-5A的LOD值由10.2增加到14.4。这表明增加群体的规模可以获得更准确的QTL定位信息。通过标记辅助回交的方法,我们构建了六个抗赤霉病QTL的近等基因系。背景选择分析表明这些近等基因系的遗传背景回复率都在97%以上。近等基因系的抗病性表现与轮回亲本绵阳99-323间存在显著差异,且与目标QTL的效应存在很高的一致性。通过筛选和鉴定重组体的方法,我们对染色体3B、4B和5A上的三个主效QTL进行了精确定位。将QFhs.nau-3B定位到Xbarc147-Xgwm493区间,将QFhi.nau-4B定位到Xgwm192-Xgwm149区间,将QFhi.nau-5A定位到Xgwm415-Xgwm304区间。更多还原

【Abstract】 Common wheat is a hexaploid species with a large and complex genome. A reference genome marker map （ITMI map） has been constructed with the recombinant inbred line population derived from a synthetic-wheat cross. But it is not sufficient for a full understanding of the wheat genome under artificial selection without comparing it with intervarietal maps. Genetic maps enriched with EST-derived markers are important to apply the genome information to crop improvement.In the present study, using the intervarietal mapping population derived from ’Nanda2419’ x ’Wangshibai’, we constructed a regional high-density genetic map of wheat with a total map length of 4243.6 cM, comprising 891 loci including 349 detected by EST-derived markers. As a supplement to the ITMI map, this map covered, mostly with the EST-derived markers, about 158 cM chromosomal regions missing in the ITMI map. The missing portion was composed of terminal portions of chromosomes 2BS, 4BL, 5AS and 5BL. In this map two-thirds of the high marker-density regions, including fifteen high-resolution mapping regions, were present in telomeric and interstitial regions. We found that the low marker density regions were largely conserved among cultivars as well as between homoeologous subgenomes. Most of the polymorphic EST-derived markers mapped to distal portions of chromosomes where the marker density and recombination rate is usually higher. QTLs/genes of agronomical importance mainly distributed on group 1, 2, 3 and 5 chromosomes and displayed a clustered distribution toward the telomeric regions. Even though the recombination rate is always low in the centromeric regions, some exceptions existed. The pericentromeric regions on chromosomes 2BL and 3BS had a recombination rate close to recombination hot spots. Alignment of the mapped ESTs with BAC/PAC clones along the rice chromosomes indicated that wheat chromosome groups 3, 6 and 7 had much better collinearity to rice chromosomes than the others. These findings would have important implications in structure and function analysis of wheat genome as well as in wheat gene mapping, cloning, and breeding programs.Type I resistance against initial penetration and type II against fungal spread within spikes are two major types of scab resistance. To map QTLs for these two types of resistance, two independent experiments usually are set up. In this study, we used the number of diseased spikelets （NDS） 14 and 21 days post spraying inoculation to reflect the combined effects of type I and type II resistance. The differences （Dnds） between NDS_D21 and NDS_D14 of each line was used to reflect the type II resistance. We found that NDS_D14 and NDS_D21 data reflected mainly the type I resistance by QTL analysis in the population used. Using D_NDS, we were able to identify all major type II resistance QTLs. Using this mothed, we found the type II QTL on chromosome 2B was also associated with type I resistance.Using a set of 277 recombinant inbred lines developed from the cross between Nanda2419 and Wangshuibai, we re-examined QTLs associated with type I resistance. The major QTLs located on 4B and 5A were mapped to the smaller marker intervals. Their LOD scores also increased greatly compared to the primary results using 136 lines. For example, the LOD score of QFhi.nau-4B increased from 4.8 to 7.6, and from 10.2 to 14.4 for QFhi.nau-5A. These results demonstrated that larger population size is useful for more precise QTL mapping.We also constructed six near-isogenic lines （NJLs） for FHB resistance QTLs through marker-assisted backcrossing. Background selection indicated that the percentage of recipient genome contents （RGC） of NILs was over 97%. The resistance performance of the NILs was significantly different from the recurrent parent Mianyang99-323, and was in accordance with the effect of target QTLs. Through selecting and evaluating recombinants, three major QTLs located on chromosomes 3B, 4B and 5A were mapped precisely. We mapped QFhs.nau-3B to Xbarcl47-Xgwm493 interval, QFhi.nau-4B to Xgwm192-Xgwm149 interval, and QFhlnau-5A to Xgwm415-Xgwm304 interval.更多还原