大穗型水稻品种弱势粒灌浆差和粒重低是阻碍水稻产量潜力发挥的主要原因之一。目前国内外主要围绕强、弱势粒灌浆差异开展了一系列生理生化及分子调控机理研究。但迄今为止，控制水稻穗粒数基因对强、弱势粒灌浆充实差异的形成及调控机制研究仍未见报道。项目组前期分离并克隆了控制水稻穗粒数基因GNP1，该基因导入增加穗粒数、剑叶叶面积、穗茎节维管束数量，但千粒重降低，尤其表现为弱势粒灌浆不饱满，千粒重显著降低。本项目以穗粒数基因GNP1近等基因系为试材，精细比较该基因在籽粒灌浆过程中强、弱势粒的胚乳细胞形态、灌浆生理生化、基因表达等多层次上的遗传效应，剖析其作用机制；并结合GNP1转基因株系强、弱势粒灌浆特性的分析，阐明GNP1基因对强、弱势粒灌浆充实差异的分子机制。研究结果对破解大穗型水稻弱势粒灌浆差的科学难题和挖掘水稻生产潜力具有重要的科学价值，对进一步通过分子育种技术培育超高产品种具有重要的指导作用。

Poor filling and low grain weight of inferior spikelets is one of the major reasons of limitation on the realization of high yield potential in the newly bred “super” rice cultivars with large number of spikelets.Although many researches focus on the physiological function and molecular mechanisms of the asynchronous filling of superior and inferior spikelets, formation and regulation mechanisms of grain number per panicle gene on differences in grain filling of superior and inferior grains has not been reported so far. Our previous study isloated and cloned GNP1 gene affecting grain number per panicle in the progenies of introgression Teqing into Lemont background through map-based cloning strategy. Compared with the NIL-GNP1LT control, we observed significant increases in grain number, flag leaf area, vascular bundle at the panicle neck and culm, and grain yield in NIL-GNP1TQ , but dramatic decrease in 1000-grain weight, especially for inferior 1000-grain weight. On the basis, genetic effect and molecular mechanisms of GNP1 gene on grain filling of superior and inferior spikelets will be compared in the levals of morphology, physiology, biochemistry and gene expression in the grain filling stage using near-isogenic lines.These results will have an important scientific value to understand regulation mechanisms on grain filling of inferior spikelets and increase the yield performance of rice, and also play an important role in guiding molecular breeding for developing super high yield rice varieties by molecular technologies.