基于淀粉精细结构动态形成解析氮素穗肥对粳米食味品质的调控机理

Closely related to the major practical problems of low eating and cooking quality of rice in current rice production in China and based on the previous studies, three typical japonica rice genotypes, i.e. general eating and cooking quality japonica rice, high eating and cooking quality japonica rice and waxy japonica rice will be selected as materials. We want to carry out the following targeted research: (1) To study and reveal the differences in the formation of fine starch structure between different genotypes and their relationship with the cooking and eating quality of rice， lucubrate the changes of rice eating and cooking quality and starch fine structure under the control of nitrogen panicle fertilizer, and elucidate the mechanism of the effect of starch fine structure formation on rice cooking and eating quality. (2) Three genotypes rice’ key starch synthetase activities dynamic changes during grain-filling stage will be studied, and the effects of nitrogen panicle fertilizer on activities of three genotypes rice’ starch key synthetase will be explicated, in order to elucidate the mechanism of key starch synthase activity on starch fine structure formation under the regulation of nitrogen panicle fertilizer. Based on the above research results and the dynamic formation of starch fine structure under the regulation of nitrogen panicle fertilizer, and finally elucidate the regulation mechanism of nitrogen panicle fertilizer on rice eating and cooking quality will be elucidated.

紧扣我国当前水稻生产中稻米食味品质普遍较低的重大实际问题，在已有研究的基础上，选用一般食味粳稻、优质食味粳稻和粳糯稻3种典型基因型粳稻为材料，开展以下针对性研究：（1）研究并揭示不同基因型粳稻淀粉精细结构的形成差异及其与稻米蒸煮食味品质间的关系，深入研究氮素穗肥调控下3种基因型粳稻稻米食味品质与淀粉精细结构的变化规律，进而阐明淀粉精细结构动态形成对稻米食味品质的影响机制。（2）研究并揭示3种基因型粳稻灌浆结实期淀粉关键合成酶活性动态变化的差异，明确氮素穗肥对3种基因型粳稻淀粉关键合成酶活性的调控效应，进而阐明氮素穗肥调控下淀粉关键合成酶活性对淀粉精细结构形成的影响机制。综合以上研究结果，基于淀粉精细结构在氮素穗肥调控下的动态形成规律，系统阐明氮素穗肥对稻米食味品质的调控机理。

明确淀粉精细结构对稻米品质的影响有利于进一步解析稻米食味品质形成机理。本研究发现：灌浆初期ADPG焦磷酸化酶和可溶性淀粉合成酶的活性增加有利于增强总淀粉和直链淀粉含量，抽穗至成熟期提高淀粉分子酶活性，可抑制颗粒结合淀粉合成酶和淀粉脱分支酶的活性，有利于支链淀粉分支度的增加。通过对不同基因型水稻品种强势粒和弱势粒的品质研究发现：较于水稻弱势粒，水稻强势粒籽粒中直链淀粉和支链淀粉长链含量更多，且在高直链淀粉含量品种中表现更显著。有关软米品种产量品质对氮素穗肥的响应：研究表明随穗肥比例的增加，两品种产量呈上升趋势，但在基蘖肥与穗肥比例为7:3和6:4处理下，产量差异不显著；糙米率、精米率、整精米率呈上升趋势，加工品质改善；垩白率、垩白度随穗肥比例的上升而增加，外观品质变劣；稻米中蛋白质含量随穗肥比例增加而上升，营养品质改善；直链淀粉含量、胶稠度随穗肥比例的增加而下降；蒸煮米饭的香气、光泽、味道、口感、食味值均随穗肥比例的增加而下降。淀粉理化特性表现为随穗肥比例的增加，直链淀粉含量呈下降趋势；淀粉颗粒分布中，大颗粒含量随穗肥比例的增加呈下降趋势，中等颗粒与小颗粒含量呈上升趋势；氮肥用量不改变水稻淀粉晶体类型，相对结晶度随穗肥比例的增加呈上升趋势；淀粉表层的近程有序性随穗肥比例的上升而下降；溶解度与膨胀势随穗肥比例的增加而上升；RVA特征值中，峰值黏度、热浆黏度、崩解值、终值黏度随穗肥比例的上升而增加，回复值随穗肥比例的上升呈下降趋势；热焓值随随穗肥比例的增加呈上升趋势，回生焓、回生度随穗肥比例的增加呈下降趋势。表明穗肥比例的增加可改变淀粉结构特性进而改善淀粉糊化特性。因此综合产量与蒸煮食味品质，南粳9108与南粳5055产量与食味品质相协调的氮肥运筹比例为7:3。本研究阐明了半糯性品种食味形成的理化机制，同时明确了相配套的氮素穗肥施用方案，为半糯性品种的培育和推广做支撑。