云南软米地方品种籽粒淀粉品质特性研究

软米是云南种植历史悠久的一类优质特色稻种,研究其籽粒淀粉品质特性对阐明优质食味米机制、改良稻米食味具有重要学术价值和现实意义。以36份云南软米地方品种为研究材料,以高直链淀粉品种、糯米品种、软米育成品种及其他育成品种为对照材料,测定不同环境下种植收获的稻谷的直链淀粉含量、胶稠度、糊化温度和RVA特征值等稻米淀粉品质指标,利用相关分析、方差分析等方法比较分析淀粉品质特性与环境稳定性。结果表明,36份云南软米地方品种的籽粒淀粉品质主要特性为:直链淀粉含量和胶稠度居中;糊化温度最高,但与对照间均无显著差异(P>0.05);RVA谱特征值中峰值黏度和崩解值较高;热浆黏度、冷胶黏度、消减值、峰值时间和起浆温度基本介于高直链淀粉品种与糯米品种之间。同时,云南软米品种(指云南软米地方品种和软米育成品种总称)与高直链淀粉品种、糯米品种和其他育成品种之间的热浆黏度、冷胶黏度、消减值存在显著差异(P<0.05)。相关分析表明,云南软米品种,尤其是云南软米地方品种,直链淀粉含量与RVA谱特征值之间存在显著相关性(P<0.05)。云南软米地方品种的籽粒淀粉品质特性受环境影响最大,10个性状中,除糊化温度外,其余9个性状均表现显著差异(P<0.05)。也发现云南软米地方品种的淀粉品质特征与其来源地有关系,来自南部边缘水、陆稻区与滇南单、双季籼稻区材料的淀粉品质特性之间存在显著差异(P<0.05)。综上,描述云南软米品种籽粒淀粉品质主要特征时,除了将直链淀粉含量作为基本描述性指标外,还需结合热浆黏度、冷胶黏度、消减值3个RVA谱特征值指标进行综合评价,也需注意云南软米地方品种籽粒淀粉品质特性的表现对环境敏感,选育广适应性软米品种难度极大。

Grain starch quality characteristics of Yunnan soft rice landraces

Soft rice is a unique, high-quality rice germplasm resource with a long history of cultivation in Yunnan Province, China. It is important to study the grain starch quality characteristics for elucidating the mechanism of high-quality rice and improving rice taste. In this study, 36 Yunnan soft rice landraces and control materials including high-amylose content (high-AC) rice varieties, glutinous rice varieties, Yunnan soft rice cultivars and other cultivars were planted and harvested in different environments. The apparent amylase content (AC), gel consistency (GC), gelatinization temperature (GT), and rapid visco analyzer (RVA) profile characteristics were determined and analyzed using correlation and variance analysis. The main starch quality characteristics of the 36 Yunnan soft rice landraces were that the AC and GC were in the middle; the GT was the highest, but there were no significant differences with the control groups (P>0.05); in the RVA profile, the peak viscosity (Peak-1) and breakdown value (Breakdown) were more higher, the hot paste viscosity (Trough-1), final viscosity (Final-Visc), and setback value (Setback), peak time (Peak-Time) and pasting temperature (Pasting-Temp) were basically between high-AC and glutinous rice varieties. Variance analysis indicated significant differences in Trough-1, FinalVisc, and Setback of RVA profile between the Yunnan soft rice varieties (general term for Yunnan soft rice landraces and Yunnan soft rice cultivars) and high-AC rice varieties, glutinous rice varieties, and other cultivars. Correlation analysis showed that there were significant correlation between AC and the RVA in Yunnan soft rice varieties (P<0.05), especially landraces. In addition, the starch quality of the Yunnan soft rice landraces were most affected by the environment compared with those of the control groups. In all 10 traits, except GT, 9 traits had showed significant differences between different environments (P<0.05). The starch quality of the Yunnan soft rice landraces were found to be related to their original sites: significant differences of starch quality were found between landraces from the paddy and upland rice planting region in the south margin and the single or double-season indica rice planting region in southern Yunnan. In summary, it is concluded that AC can be used as a basic index, Trough-1, FinalVisc, and Setback of RVA profiles should also be considered as auxiliary indexes for describing the main starch quality characteristics of Yunnan soft rice varieties. Moreover, it should also be noted that the starch quality of Yunnan soft rice landraces is strongly influenced by environmental factors. It is difficult to breed wide adaptable soft rice varieties.