Difference of Amylopectin Structure Among Rice Varieties Differing in Grain Quality and Its Correlations with Starch Physicochemical Properties

To explain the forming mechanism of taste quality in rice (Oryza sativa L.), the amylopectin structures of 50 rice varieties were characterized using improved fluorophore-assisted carbohydrate electrophoresis method that was based on DNA sequencer. The correlations between amylopectin structure and rice starch physicochemical properties were analyzed on the basis of eliminating the influence of amylose content (AC). The amylopectin structures in the 50 varieties were classified into type-I and type-II according to the chain ratio of ΣDP ≤ 11/ΣDP ≤ 24. The chain ratio of type-I amylopectin was smaller than 0.22, whereas the chains ratio of type-II amylopectin was greater than 0.26. Amylopectins of all the 15 japonica varieties belong to type-II, and those of indica varieties belong to type-I (15 varieties) and type-II (20 varieties). The ΣDP 6–11 and chain ratio of ΣDP ≤ 11/ΣDP ≤ 24 were negatively correlated (P < 0.01) with pasting temperature (PT) and relative crystallinity (RC). The ΣDP 28–34 had a negative correlation (P<0.01) with PT, but had no significant correlation with RC. The ΣDP 13–24 and ΣDP 39–49 were correlated with PT (P<0.01) and RC (P<0.05). The glutinous, low AC, and high AC varieties showed consistency to the total varieties in the correlations of ΣDP 6–11, ΣDP 28–34, and chain ratio of ΣDP ≤ 11/ΣDP ≤ 24 with PT and RC. Besides, the glutinous varieties were in agreement with the total varieties in the correlation between ΣDP 39–49 and PT; the low AC varieties in agreement with the total varieties in the correlation between ΣDP 28–34 and PT; and the high AC varieties had similar correlations between ΣDP 39–49 and PT and between ΣDP 39–49 and RC to the total varieties. The proportion of amylopectin chain was not correlated with gel consistency and Rapid Visco Analyser (RVA) profile properties despite of different amylopectin branch chain-length. Therefore, the amylopectin structure is mainly related to starch PT and RC in rice rather than GC and RVA profile properties. The short (DP 6–11), intermediate (DP 13–24), moderately long (DP 28–34), and long amylopectin chains (DP 39–49) might have functions on decreasing PT and RC, increasing PT and RC, decreasing PT, and increasing PT and RC of starch in rice grains, respectively.

摘 要利用改进的基于DNA测序仪的荧光糖电泳法对我国不同品质类型水稻品种和部分外引水稻品种的支链淀粉链长分布特征进行了测定, 在尽量排除直链淀粉含量(AC)对淀粉理化特性影响的基础上, 分析了支链淀粉结构与稻米淀粉理化特性的相关性。结果表明, 根据ΣDP≤11/ΣDP≤24的链长比值, 可将50个供试品种的支链淀粉分为I型和II型两种结构类型, I型支链淀粉的链长比值小于0.22, II型支链淀粉的链长比值大于0.26。15个粳稻品种的支链淀粉结构属II型, 35个籼稻品种中有15个品种的支链淀粉结构属I型, 20个品种属II型。相关分析结果表明, ΣDP6∼11和链长比值与起始成糊温度(PT)和相对结晶度(RC)呈极显著负相关; ΣDP28∼34与PT呈极显著负相关, 与RC的相关性不显著; ΣDP13∼24和ΣDP39∼49与PT呈极显著正相关, 与RC呈显著正相关。在糯稻、低AC和高AC品种中, ΣDP6∼11、ΣDP13∼24和链长比值与PT的相关性与在全部品种中的相关性一致, 与RC的相关性也与全部品种中的相关性基本一致。ΣDP28∼34与PT在低AC品种中, ΣDP39∼49与PT在糯稻和高AC品种中、与RC在高AC品种中的相关性也与全部品种中的相关性具有一致性。不同链长范围的支链数量比例与胶稠度(GC)和RVA谱特征值的相关性基本不显著。可见支链淀粉不同链长范围的支链数量比例主要与淀粉的PT和RC相关, 而与淀粉的GC和RVA谱特征值关系不密切。