College of Coastal Agricultural Sciences, Guangdong Ocean University, Zhanjiang, 524088, China.
Sci Rep. 2023 Aug 28;13(1):14071. doi: 10.1038/s41598-023-41241-y.
High photosynthetic efficiency is the basis of high biomass and high harvest index in castor (Ricinus communis L.). Understanding the genetic law of photosynthetic traits will facilitate the breeding for high photosynthetic efficiency. In this study, the dynamic QTL mapping was performed with the populations F and BC derived from 2 parents with significant difference in net photosynthetic rate (Pn) at 3 stages, in order to reveal the genetic structure of photosynthetic traits. In F population, 26 single-locus QTLs were identified, including 3/3/1 (the QTL number at stage I/II/III, the same below), 1/2/0, 1/2/2, 1/3/1, 0/1/1, and 1/1/2 QTLs conferring Pn, water use efficiency (Wue), transpiration rate (Tr), stomatal conductance (Gs), intercellular CO concentration (Ci) and chlorophyll content (Cc), with a phenotypic variation explained (PVE) of 8.40%/8.91%/6.17%, 5.36%/31.74%/0, 7.31%/12.80%/15.15%, 1.60%/6.44%/0.02%, 0/1.10%/0.70% and 2.77%/3.96%/6.50% respectively. And 53 epistatic QTLs (31 pairs) were identified, including 2/2/5, 5/6/3, 4/4/2, 6/3/2, 3/2/0 and 4/0/0 ones conferring the above 6 traits, with a PVE of 6.52%/6.47%/19.04%, 16.72%/15.67%/14.12%, 18.57%/15.58%/7.34%, 21.72%/8.52%/7.13%, 13.33%/4.94%/0 and 7.84%/0/0 respectively. The QTL mapping results in BC population were consistent with those in F population, except fewer QTLs detected. Most QTLs identified were minor-effect ones, only a few were main-effect ones (PVE > 10%), focused on 2 traits, Wue and Tr, such as qWue1.1, qWue1.2, FqTr1.1, FqTr6, BqWue1.1 and BqTr3; The epistatic effects, especially those related to the dominance effects were the main genetic component of photosynthetic traits, and all the epistatic QTLs had no single-locus effects except qPn1.2, FqGs1.2, FqCi1.2 and qCc3.2; The detected QTLs underlying each trait varied at different stages except stable QTLs qGs1.1, detected at 3 stages, qWue2, qTr1.2 and qCc3.2, detected at 2 stages; 6 co-located QTLs were identified, each of which conferring 2-5 different traits, demonstrated the gene pleiotropy between photosynthetic traits; 2 QTL clusters, located within the marker intervals RCM1842-RCM1335 and RCM523-RCM83, contained 15/5 (F/BC) and 4/4 (F/BC) QTLs conferring multiple traits, including co-located QTLs and main-effect QTLs. The above results provided new insights into the genetic structure of photosynthetic traits and important references for the high photosynthetic efficiency breeding in castor plant.
高光效是蓖麻（Ricinus communis L.）生物量和收获指数高的基础。了解光合性状的遗传规律将有助于培育高光效。本研究利用净光合速率（Pn）在 3 个阶段差异显著的 2 个亲本衍生的 F 和 BC 群体进行动态 QTL 作图，以揭示光合性状的遗传结构。在 F 群体中，鉴定出 26 个单基因 QTL，包括 3/3/1、1/2/0、1/2/2、1/3/1、0/1/1 和 1/1/2，分别控制 Pn、水分利用效率（Wue）、蒸腾速率（Tr）、气孔导度（Gs）、胞间 CO2 浓度（Ci）和叶绿素含量（Cc），表型变异解释率（PVE）分别为 8.40%/8.91%/6.17%、5.36%/31.74%/0、7.31%/12.80%/15.15%、1.60%/6.44%/0.02%、0/1.10%/0.70%和 2.77%/3.96%/6.50%。鉴定出 53 个上位性 QTL（31 对），包括 2/2/5、5/6/3、4/4/2、6/3/2、3/2/0 和 4/0/0，分别控制上述 6 个性状，PVE 分别为 6.52%/6.47%/19.04%、16.72%/15.67%/14.12%、18.57%/15.58%/7.34%、21.72%/8.52%/7.13%、13.33%/4.94%/0 和 7.84%/0/0。BC 群体的 QTL 作图结果与 F 群体一致，只是检测到的 QTL 较少。鉴定出的 QTL 大多为微效 QTL，只有少数为主效 QTL（PVE>10%），主要集中在 Wue 和 Tr 2 个性状上，如 qWue1.1、qWue1.2、FqTr1.1、FqTr6、BqWue1.1 和 BqTr3；上位性效应，尤其是与显性效应相关的上位性效应是光合性状的主要遗传成分，除 qPn1.2、FqGs1.2、FqCi1.2 和 qCc3.2 外，所有上位性 QTL 均无单基因效应；除在 3 个阶段检测到稳定 QTL qGs1.1、qWue2、qTr1.2 和 qCc3.2，在 2 个阶段检测到 qWue2、qTr1.2 和 qCc3.2 外，每个性状的检测 QTL 在不同阶段均有所不同；鉴定出 6 个共定位 QTL，每个 QTL 控制 2-5 个不同的性状，表明光合性状之间存在基因的多效性；在 RCM1842-RCM1335 和 RCM523-RCM83 标记区间内，包含 15/5（F/BC）和 4/4（F/BC）个共定位 QTL 控制多个性状，包括共定位 QTL 和主效 QTL。上述结果为光合性状的遗传结构提供了新的见解，为蓖麻高光效的遗传改良提供了重要参考。
