The Physicochemical Properties of Starch Are Affected by Wx in Indica Rice

Amylose largely determines rice grain quality profiles. The process of rice amylose biosynthesis is mainly driven by the waxy (Wx) gene, which also affects the diversity of amylose content. The present study assessed the grain quality profiles, starch fine structure, and crystallinity characteristics of the near-isogenic lines Q11(Wx), NIL(Wx), and NIL(Wx) in the indica rice Q11 background containing different Wx alleles. Q11(Wx) rice contained a relatively higher amylose level but very soft gel consistency and low starch viscosity, compared with rice lines carrying Wx and Wx. In addition, starch fine structure analysis revealed a remarkable decrease in the relative area ratio of the short amylopectin fraction but an increased amylose fraction in Q11(Wx) rice. Chain length distribution analysis showed that Q11(Wx) rice contained less amylopectin short chains but more intermediate chains, which decreased the crystallinity and lamellar peak intensity, compared with those of NIL(Wx) and NIL(Wx) rice. Additionally, the starches in developing grains showed different accumulation profiles among the three rice lines. Moreover, significant differences in starch gelatinization and retrogradation characteristics were observed between near-isogenic lines, which were caused by variation in starch fine structure. These findings revealed the effects of Wx on rice grain quality and the fine structure of starch in indica rice.