水稻弱势粒充实差的机理与调控

Poor filling of inferior spikelets of rice is an unsolved issue for long time in both science and production. Using elite and super rice cultivars and several rice mutants as materials and conducting experiments in the field, detached panicle in vitro culture, and cell suspension culture, this proposed project aims to investigate (1) post-anthesis changes in sugar (hexose and sucrose) and hormonal levels (content or concentration), expressions of genes related to metabolism of carbohydrates and hormones, and activities of key enzymes in sucrose-to-starch conversion in both superior and inferior spikelets and their relations with endosperm development, and the mechanism underlying possible roles of sugars and hormones in regulating endosperm development; (2) changes in hormonal levels in roots, leaves, and stems, ultra-structure of root tip cells, leaf photosynthesis, and characteristics of remobilization of carbon reserves in stems during grain filling and their relations with endosperm development; and (3) effects of the mineral nutrients of nitrogen, phosphorus, and potassium, soil moisture, nutrient management, and irrigation patterns on endosperm development of superior and inferior spikelets and their physiological and molecular mechanisms. The output of the proposed project will be able to elucidate the mechanisms underlying the poor filling of inferior spikelets at the cell, organ, and whole plant levels, to explore regulatory approaches and key cultivation techniques to enhance filling of inferior spikelets of rice, and to provide physiological and biochemical indexes for breeding new super rice varieties with large panicles and better filling of inferior spikelets.

水稻弱势粒充实差是科学和生产上长期未解决的难题。本项目以常规高产品种、超级稻品种及多种突变体为材料，通过大田试验、穗离体培养试验和细胞悬浮培养等试验，主要研究：(1)花后强、弱势粒中糖(己糖和蔗糖)和激素水平(含量或浓度)、激素和碳代谢相关基因表达、蔗糖-淀粉代谢途径关键酶活性的变化及其与胚乳发育的关系，糖和激素对胚乳发育的调控作用与机理；(2)灌浆期不同材料根、茎、叶中激素水平变化、根尖细胞超微结构、叶片光合性能、茎鞘物质运转特性与强、弱势粒中糖和激素水平、激素和碳代谢相关基因表达、蔗糖-淀粉代谢关键酶活性及胚乳发育的内在生理联系；(3)氮、磷、钾矿质营养、土壤水分、肥料运筹和灌溉方式对强、弱势粒胚乳发育的影响及其生理与分子机理。在细胞、器官和整株水平上阐明弱势粒充实不良的机制，探明促进弱势粒灌浆的调控途径和关键栽培技术，为培育弱势粒充实良好的大穗型超级稻新品种提供生理生化指标。

改善水稻等谷类作物弱势粒的充实是作物学的一个科学难题，也是进一步提高产量的重要途径。为理解和解决这一难题，本项目研究了水稻弱势粒充实不良的机理，根系形态生理、地上部物质生产与籽粒灌浆的关系，适宜弱势粒灌浆的植株氮、磷、钾含量指标和土壤水分指标、促进弱势粒灌浆的水、肥调控技术及其生理学机制，取得了重要结果：(1) 胚乳发育前期或灌浆前期弱势粒乙烯合成和细胞分裂素氧化酶/脱氢酶基因表达量高、脱落酸(ABA)和糖代谢相关基因表达量低是其胚乳发育和充实不良的重要原因；糖信号和激素信号共同调控弱势粒灌浆充实；ABA可以抑制乙烯对籽粒灌浆的不利效应；(2) 抽穗期根尖细胞中线粒体和淀粉体数目、灌浆期根系氧化力、抽穗至成熟期干重与颖花数之比以及抽穗期茎、鞘中非结构性碳水化物(NSC)与颖花数之比与弱势粒充实度呈显著正相关，增加上述数值可以改善弱势粒灌浆；(3)适宜弱势粒灌浆充实的指标为：抽穗期植株氮、磷、钾含量分别为1.78～1.82%、0.64～0.68%、1.89～1.93%；灌浆期土壤落干的低限土壤水势指标为-14～-17.5 kPa；(4)提高抽穗期糖花比(茎、鞘中NSC量与颖花数之比值)和灌浆初期籽粒中ABA 与乙烯比值是促进弱势粒灌浆的两条重要调控途径；创建的“控制低限土壤水势的轻干湿交替灌溉技术”、“因种因色氮肥施用技术”等关键技术可以改善弱势粒灌浆，进而提高产量；内源激素间的平衡协调特别是ABA 与乙烯比值的提高、籽粒中蔗糖-淀粉代谢途径关键酶活性的增强是这些技术促进弱势粒灌浆的重要生理原因。这些新认识为促进谷类作物籽粒灌浆的生理调控提供了新途径，对指导水稻优质高产育种与栽培有重要的科学和实践意义。本项目发表论文33篇，其中SCI收录11篇；培养博士和硕士研究生15名；申请国家发明专利5件；研究成果“促进稻麦物质转运和籽粒灌浆的方法与机制”于2016获教育部自然科学奖一等奖。