甘薯块根淀粉合成与淀粉品质形成机制及其调控研究

The starch composition and the structure of starch granules are key factors of starch quality in sweet potato storage root. Previous studies mainly focus on storage root starch content, components, and the ratio of amylose and amylopection. However, few studies focus on the formation of starch granule and size distribution characteristics in the process of storage root development, the synthesis of starch, physical and chemical properties, as well the mechanisms and regulatory pathways. We selected sweet potato varieties with quite different amylose content. Using fertilization, water, planting period and oter control measures, we measured the physical and chemical properties of starch, the expression and activity of starch synthesis key enzyme genes, and the distribution of starch granule formation and particle size. We studied the formation process of storage root starch, and further clarified the relation among the formation of starch grains, grain size distribution and the synthesis of starch and starch quality. We also discussed the regulatory effects of cultivation factors on the quality and the formation of sweet potato starch. The results could provide the theoretical basis and technical approaches for improving sweet potato starch quality by genetic engineering and cultivated regulation, and for developing starch application in food and non-food industries.

甘薯块根淀粉组分和淀粉粒结构是决定淀粉品质的关键因素。前人在块根淀粉含量、组分、直支链淀粉比例等方面开展了较多研究。然而，迄今关于块根膨大过程中淀粉粒形成和粒度分布特征、直支链淀粉合成、理化特性及其与淀粉品质之间的关系机制和调节途径，研究较为薄弱。本课题选用直链淀粉含量差异较大的甘薯品种，设计施肥、水分、栽插期等措施，测定淀粉理化特性、淀粉合成关键酶基因表达和活性变化、淀粉粒形成与粒度分布特征等内容，深入研究块根直、支链淀粉的形成过程，进而明确淀粉粒形成、粒度分布特征与直支链淀粉合成和淀粉品质形成的关系，探讨栽培因子对甘薯淀粉品质形成的调控效应。研究结果将为通过基因工程和栽培措施提高甘薯块根的淀粉品质提供理论依据和技术途径。

以不同优质专用型甘薯为材料，田间种植，研究了水、氮、钾及外源激素对其块根淀粉组分、淀粉粒构成及淀粉品质形成的调节效应及作用机制。研究结果表明，块根淀粉组分和淀粉粒的构成及淀粉品质受水、氮、钾等栽培因子的影响并存在基因型差异。不同甘薯品种的块根直支链淀粉含量及其比例与淀粉理化性质密切相关，直链淀粉含量越高，回复值、糊化温度越高，最高粘度值和淀粉膨胀力越低。ADPGase、SS、SSS和GBSS酶是影响块根淀粉合成积累的关键酶，其活性越高，块根淀粉含量越高。同时GBSS活性及其表达量差异可能是导致不同品种间直链淀粉含量差异的关键因素。不同品种的直链淀粉含量与中位粒径大于20μm淀粉粒体积百分数呈显著正相关，与小于20μm淀粉粒体积百分数呈显著负相关。施肥、水等栽培因素通过影响淀粉合成相关酶的活性及其表达、调控直支链淀粉的组成和粒度分布而影响其理化特性。