水稻Wx近等基因系胚乳淀粉结构的差异及其环境效应研究

The rice cooking and eating qualities are associated with the ratio of amylose and amylopectin and starch structure of endosperm. Wx gene plays a major role in determines the amylose synthesis, while many different multiple alleles have been found in the gentic locus. However, it has not well known the difference of endosperm starch structure in divers Wx alleles, and effect of environmental conditions at endosperm starch structure with Wx gene expression. The genetic of different Wx alleles affects the structure of starch in different environmental condition. In the present project, the Wx alleles near-isogenic lines are used as the basic experimental materials, the follow research will be carried out. (1) The effect of different Wx alleles on the endosperm growth, starch accumulation and the structure formation of the starch. (2) The action effect of gene expression in divers Wx alleles when the environmental conditions are changed during grain filling period and their relationships with the rice cooking and eating qualities. (3) Analysis of regulatory effect of divers Wx alleles on the dynamic changes of starch synthesis enzymes in rice kernel, the chain length distribution and starch granule structure, and the physiological mechanism of differences with different Wx alleles. We will analyze the relationships of Wx gene expressions with rice cooking and eating quality from the gene expression level to the physiological and biochemical level, and research to the mechanism of environmental effects from new angle. Through the research, it is possible to provides the necessary theoretical basis and new feasible way to tuning cultivation in rice.

稻米蒸煮和食味品质与胚乳直链淀粉和支链淀粉的比例及淀粉结构密切相关，Wx基因是控制直链淀粉合成的关键基因，在该基因座上已经发现有多个具有不同遗传效应的复等位基因。然而，水稻不同Wx等位基因表达与胚乳淀粉结构差异，以及在不同环境条件下Wx基因的表达差异对淀粉结构变化的影响，至今仍不清楚。本项目拟以不同Wx基因近等基因系为基础试验材料，（1）分析不同Wx等位基因对胚乳生长、淀粉积累和淀粉结构形成的作用效应；（2）研究结实期环境条件对不同Wx基因表达的效应及其与稻米蒸煮品质变化的关系；（3）解析不同Wx基因表达对胚乳中淀粉合成关键酶活性变化、淀粉链长分布、淀粉结晶特性的调控效应。项目将从基因表达水平到生理生化过程剖析环境条件对不同Wx基因表达的影响及其与稻米品质形成的关系，从新的视野分析环境条件影响稻米品质的作用机理，为水稻的调优栽培提供必要的理论依据和可行途径。

直链淀粉含量、胶稠度和糊化温度在很大程度上决定了稻米蒸煮和食味品质的表现。Wx基因编码颗粒型淀粉合成酶GBSSⅠ，其表达特征直接决定了稻米胚乳中直链淀粉含量的高低。然而目前对Wx基因的环境效应研究很不充分。本研究以不同的水稻Wx近等基因系为供试材料，进行有关水稻生长发育和稻米品质表现的研究。.多年的产量结果一致表现为偏籼型的Wxa、Wxin基因型水稻产量相对较高，并随着后期氮肥的增加，增产幅度相对较大。Wx基因对水稻生长的影响在抽穗前也有不可忽略的作用。随着施肥量的增加，稻米表观直链淀粉含量增加，胶稠度变短，崩解值、最高粘度下降，消减值、峰值时间增加，稻米蒸煮品质呈现随氮肥施用而显著下降的变化，且低氮水平条件下的氮肥增加更容易导致稻米品质的明显下降。Wxa、Wxin基因型水稻对后期施肥的反应较Wxb、wx基因型更为敏感。增施粒肥导致胚乳大颗粒淀粉粒所占比例增高，有增大淀粉平均粒径的趋势。wx 基因型水稻淀粉结晶度最大，Wxa、 Wxin 基因型水稻淀粉相对结晶度较小，淀粉相对结晶度与直链淀粉含量呈极显著负相关。不同Wx基因型水稻胚乳淀粉分子量分布差异较大，短支链与长支链部分均是wx 最大，Wxin、Wxa基因型水稻淀粉支链链部分较小。增施粒肥，会增加胚乳淀粉中支链淀粉短链含量，降低绝对直链淀粉含量和长B链淀粉部分含量；水分胁迫处理下(-30kpa)，其短支链部分降低，增大了直链和长支链淀粉的含量。淀粉结晶度、膨胀势等也呈现相应变化。各材料GBSS活性与Wx基因表达量呈显著正相关。随着后期施肥水平的提高，Wxa、Wxin基因表达量显著增加，wx基因表达量总体上很低，对后期施肥相对不敏感。结果显示，后期控氮是水稻调优栽培的必须注意的技术途径。