南方直播早稻苗期低温冷害耐性机理及其调控

The production of direct seeding-early rice (DSER) in double cropping had been rapidly developed in southern China, and the sowing date of DSER has been brought forward. However, DSER could be easily subjected to cold spell in later spring (CSLS) and CSLS accompanied with rainy weather combined stresses at early seedling stage, resulting in seedling difficult emergence and establishment and affecting grain yield in DSER. Therefore, based on the growth cabinet and field experiment at different sowing date, leading DSER varieties of southern China selected, could be studied the effects of different low temperature treatments on seedling growth at seedling stage. The objectives of this research are (1) to investigate its sensitive period response of low temperature, the difference in cold tolerance and screen out the test rice varieties; (2) to investigate the difference in physiology & biochemistry characteristics and molecular adaptive mechanism to response of different cold tolerance cultivars, to further elucidate the physiological and molecular mechanism and its interaction effect on seeding growth of DSER under wet and chilling combined stresses at early seedling stage. (3) to clarify the ultimate effect on grain yield components and quality characteristics under chilling damage at seedling stage, so as to establish the evaluation system of disaster damage, and further to propose the regulation approach of water and fertilizer managements, so as to establish the prevention and control technology on chilling damage at seedling stage of direct seeding rice. Our studies may provide a theoretical basis and technical support for the production of direct seeding rice and stable yield & efficient cultivation of DSER in future.

针对我国南方稻区直播早稻发展较快，播种期相对提前，但苗期易遭受“倒春寒”低温冷害及伴随阴雨天气双重胁迫的影响，导致种子难出苗成苗，影响直播稻高效、稳产等突出问题，本项目以南方稻区早稻主栽品种为研究对象，基于人工气候箱自动控温和大田分期播种方法相结合，研究苗期低温冷害对直播早稻幼苗生长的影响，明确直播早稻品种苗期耐冷性生长差异及其敏感时期，提出和建立耐冷性评价指标并筛选出不同耐性品种；阐明不同低温耐性品种苗期低温冷害生长差异的生理及分子机理及适应机制，并进一步摸清湿度与低温耦合影响直播早稻幼苗生长的作用机制及其耦合效应；同时通过大田分期播种试验，探明直播早稻苗期低温冷害对产量及品质影响的后效应特性，建立灾害评估体系，并明确低温冷害下水、肥等措施的调控途径，构建直播早稻苗期低温冷害的防控技术，为南方稻区直播稻生产发展与高效稳产抗逆栽培提供理论依据。

我国南方稻区直播早稻发展较快，播种期相对提前，且苗期易遭受“倒春寒”低温冷害及伴随阴雨天气双重胁迫的影响，导致种子难出苗成苗，但其生理生态与分子机制尚不清楚。本项目以直播早稻为研究对象，通过气候箱自动控温和大田分期播种方法，开展了直播早稻苗期冷害的耐性差异、生理生态与分子机理，以及冷害的后效应与调控等方面研究。结果表明，8℃/10d可进行苗期耐冷性鉴定，以幼苗成活率和生物量为耐冷性指标，筛选出五丰优623、湘早籼6号等为耐冷性品种，中嘉早17及株两优819等为冷敏感品种。直播早稻苗期低温冷害显著影响秧苗生长性状，破坏叶片结构，降低保护酶活性（SOD、POD、CAT）与光合酶活性（Rubisco、PEPCK、叶绿素和ATP含量）系统，增加渗透调节物质（可溶性蛋白、MDA、Pro），打乱内源生长激素平衡（ABA、GA3），以冷敏感型品种影响效应较大，而通过淹水处理可缓解低温冷害作用，转录组与蛋白质组学分析表明主要是诱导了甘氨酸、丝氨酸和苏氨酸代谢、次级代谢产物的生物合成、代谢途径、糖酵解和糖异生等蛋白通路变化。同时，低温冷害下，空气高湿（RH 95%）较低湿（RH 25%）处理通过增加O2-、可溶性蛋白含量等渗透调节物质与GSH，并降低APX、Rubisco活性和叶绿素含量、PDH和α-KGDH活性、GA3含量等生理途径来影响直播早籼稻幼苗的生长性能。此外，播期试验表明，提早播种产生的低温冷害后效应通过影响植株生长发育特性（出苗率、生育期、叶面积指数、干物质积累）降低直播稻产量，不利于稻米加工品质和外观品质提升，降低营养品质，但改善稻米蒸煮食味品质。低温冷害下，高氮或低氮淹水处理可减缓幼苗的生理损伤，改善秧苗农艺性状；同时硅钾肥配施有利于提高直播早籼稻成苗率与产量形成，缓解直播稻的低温伤害。研究结果可为南方稻区直播早稻抗逆栽培提供科学依据与技术支撑。