Table_3_Dissecting the Genetic Basis Underlying Combining Ability of Plant Height Related Traits in Maize.DOCX

Maize plant height related traits including plant height, ear height, and internode number are tightly linked with biomass, planting density, and grain yield in the field. Previous studies have focused on understanding the genetic basis of plant architecture traits per se, but the genetic basis of combining ability remains poorly understood. In this study, 328 recombinant inbred lines were inter-group crossed with two testers to produce 656 hybrids using the North Carolina II mating design. Both of the parental lines and hybrids were evaluated in two summer maize-growing regions of China in 2015 and 2016. QTL mapping highlighted that 7 out of 16 QTL detected for RILs per se could be simultaneously detected for general combining ability (GCA) effects, suggesting that GCA effects and the traits were genetically controlled by different sets of loci. Among the 35 QTL identified for hybrid performance, 57.1% and 28.5% QTL overlapped with additive/GCA and non-additive/SCA effects, suggesting that the small percentage of hybrid variance due to SCA effects in our design. Two QTL hotspots, located on chromosomes 5 and 10 and including the qPH5-1 and qPH10 loci, were validated for plant height related traits by Ye478 derivatives. Notably, the qPH5-1 locus could simultaneously affect the RILs per se and GCA effects while the qPH10, a major QTL (PVE > 10%) with pleiotropic effects, only affected the GCA effects. These results provide evidence that more attention should be focused on loci that influence combining ability directly in maize hybrid breeding.

玉米株高相关性状（包括株高、穗位高及节间数）与田间生物量、种植密度及籽粒产量紧密相关。既往研究多聚焦解析株型性状自身的遗传基础，但对配合力的遗传机制仍知之甚少。本研究采用北卡罗来纳II号交配设计（North Carolina II mating design），将328份重组自交系（recombinant inbred lines, RILs）与2个测验种进行组间杂交，共获得656个杂交组合。亲本自交系及杂交组合分别于2015年和2016年在中国2个夏玉米主产区完成表型鉴定。数量性状基因座（quantitative trait locus, QTL）定位结果显示，在针对RILs自身性状检测到的16个QTL中，有7个可同时在一般配合力（general combining ability, GCA）效应中被检测到，表明GCA效应与目标性状由不同的基因位点组遗传调控。在针对杂交组合表现鉴定出的35个QTL中，分别有57.1%和28.5%的QTL与加性/GCA效应、非加性/特殊配合力（specific combining ability, SCA）效应存在重叠，说明本研究中杂交组合表型变异由SCA效应贡献的比例较低。位于第5、10号染色体的2个QTL热点区域（包含qPH5-1和qPH10位点）已通过Ye478衍生系验证了其对株高相关性状的调控作用。值得注意的是，qPH5-1位点可同时调控RILs自身性状及GCA效应；而qPH10作为一个具有多效性的主效QTL（表型变异解释率（phenotypic variation explained, PVE）>10%），仅对GCA效应产生影响。本研究结果表明，在玉米杂交育种中应更多关注直接影响配合力的基因位点。