Ministry of Education and Jiangxi Key Laboratory of Crop Physiology, Ecology and Genetic Breeding, Jiangxi Agricultural University, Nanchang 330045, China; State Key Laboratory of Crop Gene Exploration and Utilization in Southwest China/College of Agronomy, Sichuan Agricultural University, Chengdu 611130, China.
Ministry of Education and Jiangxi Key Laboratory of Crop Physiology, Ecology and Genetic Breeding, Jiangxi Agricultural University, Nanchang 330045, China.
Food Res Int. 2023 Feb;164:112320. doi: 10.1016/j.foodres.2022.112320. Epub 2022 Dec 9.
Late-season indica rice frequently encounters low temperature (LT) along with low light (LL) after heading in southern China, which deteriorates the grain quality by altering starch quality. However, the detailed effects on starch properties of these stressors remain unclear. Herein, two indica rice cultivars with good and poor grain quality were grown under control (CK), LT, and LT + LL conditions after heading and the structural and physicochemical properties of their starch were evaluated. Compared with CK, LT and LT + LL worsened thermal and pasting properties of starch in the two cultivars, mainly because they increased branch chain branching and A chain (DP ≤12), and decreased average branch chain length and crystallinity. Compared with LT, LT + LL deteriorated the pasting properties of the poor-quality cultivar, such as reducing breakdown (BD), final and peak viscosity, which mainly owing to decreasing the starch branching and crystallinity degrees, and increasing the small starch granules (d < 10 μm). Gelatinization enthalpy and BD both had significant and positive correlations with amylose content, the ratio of amylose and amylopectin, B3 chain and crystallinity. Taken together, these results suggest that LT and LT + LL during grain filling can deteriorate the physicochemical properties of starch in late-season indica rice cultivars by disrupting starch multilevel structure, especially upon LT + LL. In particular, while poor-quality cultivar had poorer physicochemical properties, the good-quality cultivar had poorer thermal properties under LT + LL.
晚季籼稻在华南抽穗后常遭遇低温（LT）和低光照（LL），这会通过改变淀粉质量来降低稻谷品质。然而，这些胁迫因素对淀粉性质的详细影响仍不清楚。本研究在抽穗后，以两个具有良好和较差稻谷品质的籼稻品种为材料，在对照（CK）、LT 和 LT+LL 条件下进行生长，并评估其淀粉的结构和理化性质。与 CK 相比，LT 和 LT+LL 恶化了两个品种淀粉的热特性和糊化特性，主要是因为它们增加了支链分支和 A 链（DP≤12），降低了平均支链长度和结晶度。与 LT 相比，LT+LL 恶化了低品质品种的糊化特性，如降低了崩解值（BD）、最终黏度和峰值黏度，这主要是由于淀粉分支和结晶度降低，以及小淀粉颗粒（d<10μm）增加所致。凝胶化焓和 BD 与直链淀粉含量、直链淀粉与支链淀粉的比例、B3 链和结晶度均呈显著正相关。综上所述，这些结果表明，在灌浆期，LT 和 LT+LL 可通过破坏淀粉多层次结构，特别是 LT+LL，使晚季籼稻品种的淀粉理化性质变差。特别是在 LT+LL 条件下，低品质品种的理化性质较差，而高品质品种的热特性较差。
