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

Grain yield improvement in wheat (Triticum aestivum 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 Xbarc99 and Xbarc169 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.

普通小麦（Triticum aestivum L.）的籽粒产量提升，有赖于解析产量组分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，采用单变量QTL分析与多变量QTL分析分别开展定位，共获得82个与收获后籽粒产量及产量组分相关的数量性状位点（quantitative trait loci, QTL），以及314个与苗期、抽穗期和灌浆期光合性状相关的QTL。共61个QTL簇可解释2至76个性状的表型变异，解释率范围为4.42%~27.72%。通过单变量与条件QTL定位结果的对比分析发现，在5个QTL位点上，籽粒产量与产量组分及光合性状均存在显著的遗传相关。在1D染色体上Xbarc99与Xbarc169之间的遗传区段内，籽粒产量的遗传效应完全由千粒重与收获指数贡献。在同一遗传区段内，收获指数的遗传效应分别由苗期蒸腾速率、胞间CO₂浓度、气孔导度、净光合速率及抽穗期蒸腾速率，以及灌浆期胞间CO₂浓度、净光合速率与蒸腾速率共同贡献；而该区域内千粒重则受到灌浆期叶绿素含量相关单变量QTL的负向调控。籽粒产量与光合性状的直接对比分析也表明，该区域内二者存在相似的遗传关联模式。对这些QTL簇内的基因进行精准调控，有望改良重要农艺性状并提升籽粒产量。