灌浆期遮光对糯小麦和非糯小麦淀粉组分及理化特性的影响

Effects of Shading at Grain Filling Stages on Starch Components and Physicochemical Properties of the Waxy Wheat and Non-Waxy Wheat

【目的】揭示灌浆期遮光对糯小麦和非糯小麦籽粒淀粉理化特性影响的差异,探讨籽粒淀粉组分与理化特性的内在联系。【方法】大田条件下,选用非糯小麦品种轮选987和糯小麦品种农大糯50222,分别于灌浆前期(花后1—10 d)、灌浆中期(花后11—20 d)和灌浆后期(花后21—30 d)遮去60%的光合有效辐射处理,以大田自然光强为对照(CK),研究灌浆期遮光对糯小麦和非糯小麦籽粒淀粉组分和理化特性的影响。【结果】灌浆期遮光显著降低小麦籽粒总淀粉、直链淀粉和支链淀粉含量,其中灌浆前期遮光降低幅度最大,而灌浆后期最小,且弱光对轮选987总淀粉含量的影响大于农大糯50222。灌浆期遮光轮选987直/支比值增大;而农大糯50222的直/支比值在灌浆前期和中期遮光后减小,灌浆后期遮光无变化;灌浆前期和后期遮光显著提高轮选987淀粉B型淀粉粒的体积、表面积和数目比例,降低A型淀粉粒的体积、表面积和数目比例,而灌浆中期遮光则呈相反趋势。灌浆期遮光均显著提高了农大糯50222淀粉B型淀粉粒的体积、表面积和数目比例,降低了A型淀粉粒的体积、表面积和数目比例。灌浆期遮光两小麦淀粉的相对结晶度呈降低趋势,遮光对其影响程度随遮光时期的延迟而减小,且农大糯50222淀粉的相对结晶度显著大于轮选987。灌浆前期和灌浆中期遮光降低了轮选987淀粉的峰值黏度、谷值黏度、最终黏度和稀懈值。灌浆各时期遮光均降低了农大糯50222淀粉的上述指标,但仍高于轮选987。相关性分析表明,直链淀粉含量、直支比值与最终黏度、反弹值、峰值黏度、谷值黏度及糊化时间呈显著负相关,支链淀粉含量与其呈显著正相关。B型淀粉粒的体积比例与最终黏度和反弹值呈显著负相关。B型淀粉粒表面积比例和相对结晶度、最终黏度、反弹值、糊化时间呈显著正相关,与糊化温度呈显著负相关。【结论】灌浆期遮光改变了小麦胚乳淀粉组分、粒度分布、相对结晶度及其主要糊化特征参数。小麦胚乳淀粉组分与晶体特性和糊化特性之间均存在明显的相关性,表明遮光影响了小麦淀粉组分,间接影响了其理化特性。

[Objective] The objective of this experiment is to comprehensively study the effects of shading at grain filling stage on physicochemical properties of waxy wheat and non-waxy wheat starch, and reveal the intrinsic relationship between the starch components and physicochemical properties of wheat starch. [Method] In fields, waxy wheat cultivar Nongdanuo 50222 and non-wary wheat cultivar Lunxuan 987 were used as the material to investigate the effects of shading at grain filling stage on starch components and physicochemical properties. The photosynthetic active radiation was cut offby 60% at early grain filling stage （1-10 d）, middle grain filling stage （11-20 d） and later grain filling stage （21-30 d）, the natural condition was taken as the control （CK）. [ Result] The content of total starch, amylose and amylopectin were decreased significantly after shading at grain filling stage, the effect of shading at early grain filling stage was maximum, while later grain filling stage was minimum, and starch content of Lunxuan 987 was much more sensitive to shading than Nongdanuo 50222. The amylose/amylopectin ratio of Lunxuan 987 was increased at each shading treatment during the grain filling, while Nongdanuo 50222 was decreased at the early and middle grain filling stages. The B-granules volume, surface and number proportion of Lunxuan987 increased significantly, and those of A-granules decreased after shading at early and later grain filling stages. The B-granules volume, surface and number proportion of Nongdanuo 50222 were increased, while those of A-granules decreased at each shading stage. The relative crystallinity of starch was decreased after shading at grain filling stage, and with the shading delaying, the effects on relative crystallinity were decreased. But the relative crystallinity of Nongdanuo 50222 starch was significantly greater than Lunxuan 987. The peak viscosity, valley viscosity, final viscosity and breakdown value of the Lunxuan987 starch were decreased after shading at early and middle grain filling stages. While the above indexes of Nongdanuo 50222 starch were decreased and significantly higher than Lunxuan 987 starch at each shading stage. Correlation analysis showed that the amylose content and the amylose/amylopectin ratio were negatively correlated with the final viscosity, setback value, peak viscosity, valley viscosity and pasting time. The amylopectin content was positively correlated with the above indexes. The B-granules volume proportion was negatively correlated with the final viscosity and setback value. The B-granules surface proportion had a significant positive correlation with relative crystallinity, final viscosity, setback value and pasting time, and was negatively correlated with pasting temperature. [ Conclusion] Shading at different grain filling stages changed the wheat endosperm starch composition, granule size distribution, relative crystallinity and pasting parameters. There were significant correlations between wheat endosperm starch components and physicochemical properties, which indicated that the effects of shading on starch components indirectly affected the physicochemical properties of wheat.