Amylose content in rice: integrating genetics, grain filling physiology, and breeding strategies

Rice is a major staple crop worldwide, and variation in starch composition is a key determinant of grain quality, end-use functionality, and breeding value. Among starch components, amylose content (AC) plays a central role in defining the physicochemical properties of rice grains and reflects the coordinated regulation of starch biosynthesis during endosperm development. This review provides an integrated analysis of amylose variation in rice from a genetics-physiology-breeding perspective, based on a structured literature search using PubMed, Scopus, Web of Science, and Google Scholar covering studies published between 2000 and 2026. The analysis synthesizes current knowledge on the molecular regulation of amylose biosynthesis, with emphasis on the Waxy (Wx) gene and associated enzymes within the starch biosynthetic network, as well as on grain filling physiology, source-sink carbon partitioning, and environmental modulation of amylose accumulation. In addition, we examine natural genetic variation across rice germplasm and evaluate breeding strategies, including marker-assisted selection, genomic selection, and genome editing approaches, for optimizing amylose content and grain quality. Evidence indicates that amylose accumulation is governed by complex interactions among genetic, physiological, and environmental factors that collectively determine starch structure, grain functionality, and stability across production environments. By linking molecular mechanisms, physiological processes, and breeding strategies, this review provides a framework for the development of rice cultivars with stable amylose profiles, predictable grain quality, and improved adaptation to diverse agroecological conditions.