稻米品质形成对臭氧胁迫的应答机制及调控

In recent years, the rapid increase in tropospheric ozone concentration has been considered as a threat to food security in Asia. Ozone enters the plants' leaves through the stomata during photosynthetic gas exchange and induces numerous physiological stress reactions in plants that can alter the chemical composition of crops and thus the quality of the harvested products. Rice is one of the most important crops in the world, which provides the dietary staple for more than half of the world's population. With the rapid growth in world population and the improvement in living standard, the coming decades will see soaring demand for rice, especially high quality rice. However, unlike with the grain yield, little information is available on the effects of ozone on the rice quality. A few investigations conducted so far point out a general negative trend on the responses of rice quality to ozone exposure. In view of the importance of grain quality in human diet, objectives of the proposed research is to elucidate how grain qualities of rice, including milling quality, appearance quality, eating/cooking quality and nutritional quality will change under elevated ozone concentrations. The growth chamber facilities with natural light and the free-air gas concentration enrichment (FACE) system for ozone fumigation will be used. Based on previous yield performance, rice cultivars and breeding lines with contrasting tolerance to ozone stress will be tested in quality research. The multi-fator design will be applied to study the effects of elevated ozone on rice quality and its interaction with cultivation measures. The physiological mechanisms responsible for rice quality changes under elevated ozone concentration will be studied through investigating the key metabolism processes during grain filling stage. The results of this research will provide crucial information for target breeding of ozone tolerant rice cultivar with superior quality and developing new cultivation technology?for better rice production.

近年来不断上升的近地层臭氧浓度是威胁亚洲粮食安全的主要环境逆境之一。臭氧通过叶片气孔进入植物体内并引发一系列生理代谢过程的变化，将会导致植物可食用部位生化组成的改变进而最终影响品质。水稻是重要的粮食作物，随着人口的增长和生活水平的提高，未来世界对优质稻米的需求将持续增加。前期研究发现，臭氧胁迫下杂交稻汕优63稻米品质总体变劣，但这种现象的普遍性及其作用机制尚不清楚。本项目利用环境条件接近自然农田的自由空气中微量气体浓度升高（FACE）平台和日光智能气候室，选用对臭氧响应差异显著的水稻基因型为供试材料，设置多因子操作试验，研究近地层臭氧浓度增高对稻米品质的影响及其农艺调控途径；通过籽粒灌浆期主要生理代谢过程与成熟期稻米品质对臭氧响应的综合分析，明确稻米品质形成对臭氧应答的主要生理指标和关键代谢步骤，阐明臭氧影响稻米品质的生理基础，为培育抗臭氧优质水稻品种以及栽培技术的更新提供科学依据。

地表臭氧浓度增高是威胁亚洲粮食安全的主要环境逆境之一。水稻是人类最重要的粮食来源之一，高产和优质是稻作生产的两大目标，大气变化背景下稻作生产的适应策略必须同时考虑品质；但相比产量，稻米品质形成对臭氧胁迫的应答机制及其调控的研究非常有限。大型气体熏蒸平台的出现为回答这些问题提供了良机。本项目利用自由空气中微量气体浓度升高（FACE, Free-Air gas Concentration Enrichment）系统和日光智能气候室，以在产量方面对臭氧响应差异显著的水稻基因型为供试材料，设置多因子操作试验，研究地表臭氧浓度增高对稻米品质的影响及其调控机理。结果表明，地表臭氧浓度增高环境下生长的水稻显著减产，同时也使稻米品质总体变劣。臭氧胁迫使稻米加工后碎米增多，垩白粒率和垩白度显著增加，元素浓度多呈增加趋势；臭氧胁迫稻米的蛋白质和氨基酸组分含量增加，但其单位面积产量明显下降。臭氧胁迫下稻米蒸煮食味品质亦呈变劣趋势，表现在最高粘度和崩解值减小，但消减值和糊化温度增加。臭氧胁迫导致的垩白增加与籽粒灌浆期叶片碳水化合物和氮水平下降有关，两者均以敏感品种的改变更为明显。臭氧胁迫下稻米蛋白质浓度增加主要与水稻氮素分配策略的改变有关，表现在叶片氮代谢相关酶活性（如谷氨酰氨合成酶GS和谷氨酸合酶GOGAT）的响应。臭氧胁迫对稻米品质影响的基因型差异与有无耐臭氧基因位点（OzT8/OzT9）密切相关，后者部分解释了稻米品质响应的生理过程。多因子互作研究发现，地表臭氧浓度增高对水稻产量和品质性状的影响多与生长季、基因型、籽粒着生位置以及熏蒸平台等因子有关，但臭氧处理与移栽密度、叶面施锌等因子间的交互作用较弱。上述结果对通过育种途径培育耐臭氧优质水稻品种以及未来栽培技术的更新有参考价值。项目实施期间，研究小组合计发表标注基金资助的相关论文15篇，其中SCI收录3篇、CSCD收录论文11篇、英文书籍章节1篇；另外，指导完成研究生毕业论文9篇。