基于碳氮代谢解析水稻产量和品质协同提升的生理机制

Great attention has always been paid to how to improve synergistically rice grain yield and quality (especially taste quality). The coordinated interaction of carbon and nitrogen metabolism during grain filling is related directly to the formation of rice grain yield and quality. This project will conduct the following researches: (1) High-yielding genotypes with superior taste quality, high-yielding genotypes with inferior taste quality, and low-yielding genotypes with superior taste quality are selected as materials. The changes and differences of assimilates and nutrient accumulation, distribution, and translocation, metabolites and activities of key enzymes involved in carbon and nitrogen metabolism of leaf and grain of these genotypes are compared. Such comparisons are intended to clarify the interaction characteristics of carbon and nitrogen metabolism during grain filling in different genotypes, and their relationships with the formation of rice grain yield and quality. (2) Taking the high-yielding genotypes with superior taste quality as the further research material. The differences in metabolites and activities of key enzymes involved in carbon and nitrogen metabolism of plants, and grain yield and quality under different nitrogen rates and shading treatments are compared. Such differences are compared to clarify the interaction characteristics of carbon and nitrogen metabolism during grain filling under different nitrogen rates and shading treatments, and their relationships with the formation of rice grain yield and quality. Based on the above, we intend to clarify interaction characteristics of carbon and nitrogen metabolism during grain filling at genotypic and environmental levels, and their effects on the formation of rice grain yield and quality. This project is aimed to reveal physiological mechanism of synergistic improvement of rice grain yield and quality based on carbon and nitrogen metabolism, which could provide scientific supports for breeding high-yielding variety with good quality (especially taste quality) and cultivation optimization.

如何协同提升水稻产量和品质（特别是食味品质）一直备受关注。结实期植株碳氮代谢协调互作直接关系到水稻产量和品质的形成，本项目拟开展以下研究：(1)以前期品种试验筛选出的高产味优、高产味劣、低产味优三类基因型为试验材料，比较不同基因型结实期植株干物质和养分积累与分配转运、叶片和籽粒碳氮代谢产物与关键酶活性等的变化与差异，明确不同基因型结实期植株碳氮代谢互动特性及其对水稻产量和品质形成的影响效应。(2)以高产味优基因型为进一步研究对象，比较其在不同氮肥用量和遮光处理下结实期植株碳氮代谢特征、水稻产量和品质的差异，揭示不同氮肥用量与光照条件下结实期植株碳氮代谢互动特性及其对水稻产量和品质形成的影响效应。通过明晰结实期植株碳氮代谢互动特性的基因型差异、环境效应及其对水稻产量和品质形成的影响，从碳氮代谢角度解析水稻产量和品质（特别是食味品质）协同提升的生理机制，为品种改良和栽培调优提供科学依据。

水稻产量和食味品质协同提升的碳氮代谢机制仍有待进一步研究明确。以筛选出的高产味优、高产味劣、低产味优典型基因型为试材，研究了结实期植株碳氮代谢互动特性的基因型差异、环境效应及其与水稻产量和品质形成的内在联系，主要结果如下。.（1）高产味优和高产味劣基因型产量显著高于低产味优基因型。高产味优和低产味优基因型食味值均在70以上，显著高于高产味劣基因型（平均为56.7）。高产味优基因型在产量构成上穗多粒大、库容大（单位公顷颖花量44000万），粒重则相对较小（26-27 g）。高产味优基因型外观品质介于高产味劣和低产味优基因型之间；直链淀粉含量低（13.0%），胶稠度长（75 mm以上），蛋白质含量8.0%-8.2%，且具有较高的谷蛋白与醇溶蛋白含量比值。.（2）与高产味劣和低产味优基因型相比，高产味优基因型成熟期群体干物重高，收获指数则低于高产味劣基因型；成熟期植株氮素积累量大，叶片含氮率高，籽粒含氮率较低。高产味优基因型花后植株叶绿素含量、光合速率、叶面积指数均高于高产味劣和低产味优基因型。与高产味劣和低产味优基因型相比，高产味优基因型花后各阶段AGP和SBE酶活性均较高，且差异显著；SSS和GBSS酶活性则在不同类型基因型之间无明显趋势。灌浆前期不同类型基因型GS和GOGAT酶活性无明显趋势，灌浆中期和后期则以高产味优基因型显著高于高产味劣和低产味优基因型。.（3）不同生育阶段遮光均造成水稻产量和食味值的下降，且以抽穗至成熟期遮光处理的降幅更大。拔节至抽穗期遮光处理造成水稻减产主要是由于较低的每穗粒数，拔节至抽穗期遮光处理造成水稻减产则主要是由于较低的结实率和千粒重。与CK（无遮光处理）相比，拔节至抽穗期、抽穗至成熟期遮光处理降低了花后植株叶片光合速率，导致成熟期群体干物重下降，收获指数亦较低。CK处理中，稻米加工和外观品质均以N270氮肥用量下最高，遮光处理中则以N225氮肥用量下最高。遮光处理下，提高氮肥施用抑制了植株光合同化积累能力，光合产物输出减少，导致籽粒淀粉含量下降而蛋白质含量上升，稻米食味品质变差；适当降低氮肥施用则利于同化物转运，促进籽粒充实，提高稻米外观与食味品质。.本研究可对高产味优水稻的遗传改良和栽培调优提供理论与实践支撑。