Poor grain filling, characterized by incidence of partially filled grain, is one of the major problems to be improved for maximizing the yield potential in rice (Oryza sativa L.) cultivars with numerous spikelets in a panicle (extra‐heavy panicle type [EHPT]). This study evaluated the grain‐filling‐related alleles at APS2 and APL2, the loci for the small and large subunits of ADP‐glucose pyrophosphorylase (AGPase), respectively, and at SUT1, sucrose transporter, for their effects and interactions on grain filling and associated traits of EHPT cultivars. Two sets of derived lines were developed. Each of these lines was one of the eight possible homozygotes of alleles derived from rice cultivars Akenohoshi and Milyang 23 at the three loci in nearly common genetic backgrounds. They were examined for grain‐filling traits in two different years. Results showed that APL2‐2, and SUT1‐2 in part, derived from Milyang 23 showing relatively good grain filling, significantly improved grain filling compared with APL2‐1 and SUT1‐1 from Akenohoshi showing poor filling. This improvement in grain filling may result from increased AGPase activity and expression of APL2 and SUT1 proteins, by means of APL2‐2 and SUT1‐2. However, the variations in AGPase activity, protein expression, and the degree of grain filling were not associated with the gene expression of the three loci, implying post‐transcriptional regulation. These results strongly suggested that APL2‐2 and SUT1‐2 are associated with good grain filling.

中文翻译：

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常见遗传背景下与水稻籽粒灌浆有关的OsAGPS2，OsAGPL2和OsSUT1等位基因的评估

以部分灌浆的谷物为特征的籽粒灌浆不良是最大的问题之一，是要使穗部（超重穗型[EHPT]）中有许多小穗的水稻（Oryza sativa L.）品种的产量潜力最大化。 ）。这项研究评估了APS2和APL2葡萄糖小分子和大亚基的基因座APS2和APL2的谷物填充相关等位基因，以及SUT1，蔗糖转运蛋白，因为它们对EHPT品种的籽粒灌浆和相关性状的影响和相互作用。开发了两组衍生品系。这些系中的每一个都是在几乎相同的遗传背景下，在三个基因座的水稻品种Akenohoshi和Milyang 23衍生的八个等位基因的纯合体之一。他们在两个不同的年份检查了谷物的充实性状。结果表明，APL2-2，和SUT1-2部分地由密阳23衍生出相对良好的灌浆，显著改善籽粒灌浆相比APL2-1和SUT1-1来自Akenohoshi的填充效果很差。谷物填充的这种改善可能是由于AGPase活性增加以及通过APL2-2和SUT1-2增强了APL2和SUT1蛋白的表达所致。但是，AGPase活性，蛋白质表达和籽粒充实程度的变化与这三个基因座的基因表达无关，这意味着转录后调控。这些结果强烈表明APL2-2和SUT1-2与良好的谷物填充相关。