小麦茎秆贮积碳水化合物的基因定位与优异等位变异发掘

Water-soluble carbohydrates (WSC) accumulated in wheat stems are an important carbon source for grain weight and yield. The main storage form of WSC in wheat stems is fructans. Three different fructosyltransferases are believed to be involved in wheat graminan-type fructans biosynthesis,i.e.,sucrose:sucrose 1-frctosyltransferase (1-SST), sucrose:fructan 6-fructosyltransferase (6-SFT), and fructan:fructan 1-fructosyltransferase (1-FFT). The enzyme activities of 1-SST and 6-SFT are positively correlated with stem WSC and fructan contents, and they are the key enzymes for graminan biosynthesis. Previously, 1-SST and 6-SFT genes have been cloned, but their allelic variations have not been well characterized in common wheat. Characterization of 1-SST and 6-SFT genes and development of functional markers for them are of high importance for marker-assisted selection in wheat breeding. .In this project, the full-length genomic DNA (gDNA) sequences of 1-SST and 6-SFT genes will be characterized by PCR amplification and experimental validation in Chinese winter wheat cultivars. The functional markers will be developed based on polymorphisms of allelic variants of 1-SST and 6-SFT in cultivars with higher and lower WSC and fructan contents, respectively. The allele-specific markers of both genes will be mapped using a set of Chinese Spring nullisomic-tetrasomic lines and ditelosomic lines, and a RIL population from the cross of PH82-2/Neixiang 188. Meanwhile，the WSC and fructan contents will be measured in wheat stem of the mapping population, and used for quantitative trait loci (QTL) mapping. The genetic effects of two genes 1-SST and 6-SFT on WSC and fructan contents, co-segregating with the functional markers, will be estimated in the the mapping population. A total of 260 Chinese wheat cultivars and advanced lines will be used to validate the association between the functional markers and stem carbohydrate content, and to understand the distribution of allelic variations of 1-SST and 6-SFT genes. Cultivars carrying both favorable alleles for the two genes could contribute a significant increase in grain yield. Therefore, employing the 1-SST and 6-SFT markers in wheat breeding programs would contribute to the development of high yielding cultivars.

小麦茎秆水溶性碳水化合物（WSC）贮积量对提高粒重和产量具有重要贡献。果聚糖是WSC的主要贮藏形式，受1-SST和6-SFT两个关键合成酶调控，发掘该调控酶不同等位基因，开发并验证其特异性分子标记，对培育高产品种具有重要价值。本项目拟利用1-SST和6-SFT基因序列，克隆不同等位基因，通过分析高、低WSC和果聚糖含量品种的基因序列差异，开发WSC和果聚糖含量的基因特异性功能标记。利用中国春缺体-四体对标记进行定位。应用PH82-2/内乡188群体定位WSC和果聚糖含量主效QTL，并确定1-SST和6-SFT基因的位置和效应，及其与控制WSC、果聚糖含量主效QTL关系。测定我国冬麦区260份品种碳水化合物含量，验证新开发的功能标记，评价标记实用性，鉴定两个关键酶基因的表达模式，筛选携带优异等位基因品种，为利用分子标记辅助选择快速改良产量潜力提供理论依据。

克隆了位于普通小麦染色体4A、7A和7D上的果聚糖合成酶关键基因TaSST，利用7D上TaSST-D1基因1,216位点的SNP，开发了CAPS标记WSC7D。在豆麦/石4185RIL群体中发现TaSST-D1基因与SNP标记 BS00108793_51 紧密连锁，遗传距离为6.1cM，解释10.9%的表型变异。除TaSST-D1之外，在该群体中还定位两个QTL (QWSC.caas-4BS 和 QWSC.caas-7AS)。关联分析发掘出与茎秆碳水化合物相关联的等位变异为127个，关键合成酶基因6-SFT-4A和1-SST-7D分别解释表型变异为6.5%和8.9%。京冬8号/矮抗58群体在灌溉和节水条件下发现3个控制苗期植被覆盖率、2个控制植被归一化指数、2个控制株高、3个控制千粒重及一些叶片衰老有关的QTL，这些位点有利于提高品种的抗旱节水能力。明确了影响倒伏的关键性状，提高茎秆可溶性糖含量和基部茎秆强度有利于提高品种的抗倒伏能力，并筛选出泰农18、济宁12、临麦2号、烟农24、济麦22和良星66等优秀抗倒伏品种。苗期植被覆盖率可作为鉴定植株生长势的重要指标用于品种产量改良和遗传研究。起身期的植被覆盖率能够有效反映叶面积指数和单位面积穗数，并与籽粒产量显著相关。共检测出12个遗传区段与植被覆盖率相关联, 大部分区段直接参与调控苗期和孕穗期的生长势。并发现3个控制植被覆盖率的遗传区段与已报道的苗期性状位点一致，另外9个控制植被覆盖率的遗传区段有待验证。京411 衍生后代的产量和收获指数均随世代增加呈逐渐上升趋势，其中收获指数增加较为显著。两种施肥条件下中麦175 具有较高且稳定的产量和生物学产量, 主要与其较高的肥料吸收效率有关。京411 携带31 个对产量和生理性状为正向效应的等位基因，衍生品种CA0958 和中麦175 携带的正向效应区段最多，中麦175 的高产潜力和广适应性可能与其携带较多有利等位基因有关。