The accomplishment of further optimization of crop productivity in grain yield and quality is a great challenge. Grain size is one of the crucial determinants of rice yield and quality; all of these traits are typical quantitative traits controlled by multiple genes. Research advances have revealed several molecular and developmental pathways that govern these traits of agronomical importance. This review provides a comprehensive summary of these pathways, including those mediated by G-protein, the ubiquitin–proteasome system, mitogen-activated protein kinase, phytohormone, transcriptional regulators, and storage product biosynthesis and accumulation. We also generalize the excellent precedents for rice variety improvement of grain size and quality, which utilize newly developed gene editing and conventional gene pyramiding capabilities. In addition, we discuss the rational and accurate breeding strategies, with the aim of better applying molecular design to breed high-yield and superior-quality varieties.

在粮食产量和品质方面实现作物生产力的进一步优化是一个巨大的挑战。粒级是水稻产量和品质的关键决定因素之一；这些性状都是典型的多基因控制的数量性状。研究进展揭示了几种控制这些具有农艺重要性的性状的分子和发育途径。本综述全面总结了这些途径，包括由 G 蛋白、泛素-蛋白酶体系统、丝裂原活化蛋白激酶、植物激素、转录调节因子以及贮藏产物生物合成和积累介导的途径。我们还总结了利用新开发的基因编辑和常规基因金字塔功能改进水稻品种籽粒大小和品质的优秀先例。