Contribution of photosynthetic- and yield-related traits towards grain yield in wheat at the individual quantitative trait locus level

Grain yield improvement in wheat (<i>Triticum aestivum</i> L) requires understanding of the genetic control of grain yield components and other related traits. In this study, a total of 82 and 314 quantitative trait loci (QTLs) were associated with grain yield and grain yield components after harvest and photosynthetic traits at the seedling, heading and grain filling stages from a recombinant inbred line population by normal and multivariate QTLs analysis, respectively. Sixty-one QTL clusters explained from 4.42% to 27.72% of phenotypic variances for 2–76 traits. A comparison between the normal and conditional QTL mapping found that grain yield showed significant genetic correlation with grain yield components and photosynthetic traits on five QTLs. In the genetic region between <i>Xbarc99</i> and <i>Xbarc169</i> on chromosome 1D, grain yield was entirely contributed by thousand kernel weight and harvest index. At the same region, harvest index was contributed by transpiration rate at seedling stage, intercellular CO₂ concentration, stomatal conductance, net photosynthetic rate and transpiration rate at heading stage; and intercellular CO₂ concentration, net photosynthetic rate and transpiration rate at grain filling stage, whereas thousand kernel weight was suppressed by a normal QTL for chlorophyll content at grain filling stage in this region. The direct comparison analyses between grain yield with photosynthetic traits showed similar genetic relationships in this region. Manipulation of genes found within these QTL clusters might improve important agronomic traits and grain yield.

小麦（普通小麦*Triticum aestivum* L.）的籽粒产量改良，有赖于解析产量构成性状及其他相关性状的遗传调控机制。本研究以重组自交系（recombinant inbred line, RIL）群体为材料，分别通过单变量数量性状位点（quantitative trait loci, QTL）分析与多变量QTL分析，共鉴定得到82个与收获后籽粒产量及产量构成性状相关的QTL，以及314个与幼苗期、抽穗期和灌浆期光合性状相关的QTL。共计61个QTL簇可解释2至76个性状4.42%至27.72%的表型变异。单变量QTL定位与条件QTL定位的比较分析表明，在5个QTL位点上，籽粒产量与产量构成性状及光合性状均存在显著遗传相关。在1D染色体上Xbarc99与Xbarc169标记区间的遗传区域内，籽粒产量完全由千粒重与收获指数共同决定。该区域内，收获指数由幼苗期蒸腾速率、胞间CO₂浓度、气孔导度、抽穗期净光合速率与蒸腾速率，以及灌浆期胞间CO₂浓度、净光合速率与蒸腾速率共同调控；而千粒重则受到该区域内灌浆期叶绿素含量相关常规QTL的负向调控。籽粒产量与光合性状的直接比较分析也在该区域揭示了相似的遗传关联模式。靶向调控这些QTL簇内的基因，有望改良重要农艺性状并提升籽粒产量。