干旱胁迫对油菜种子萌发和成苗的影响及其分子应答机制研究

Autumn drought is a major obstacle to gerimination and seedling establishment of rapeseed (Brassica napus L.) in Yangtze River basin, it is of great importance to study the mechnism of germination under drought stress for the stable production of edible oil and development of fallow field. 1057 varieties from 34 countries will be used to identify the drought tolerance in this reserch. The varieties, differing in response to drought stress, will be chosen to conduct the different degree and model of drought stress test, finally ascertain the water requirment threshold during germination and emergence and the parameters of morphology index to evaluate drought tolerance; the physiology indexes of varieties with different drought stress tolerance will be determined and analyze the biochemical response pathway to drought. The method of high-throughput sequencing will be used to identify the difference of gene expression, screening for the EST sequence related to drought tolerance. The methods of bioinformatics and computer model will be applied in the research to build a drought stress adaptation mechanism during germination and emergence of rapeseed from temporal changes. The findings of this project have important significance of the scientific theory and practical application, it is beneficial to the drought-resistant breeding and the development and application of excellent gene resources of rapeseed, meanwhile the seed treatment reagents that improve germination under drought stress will be screened out, furthermore, the agronomic measures that promote germination under drought condition will be proposed, finally, it will make the full stand of rapeseed in a large area under water deficit come ture.

秋旱频发对长江流域油菜播种出苗造成很大障碍，研究干旱萌发机理对解决我国食用油稳定生产及冬闲田开发难题十分重要。本研究拟采用来自34个国家的1057品种资源进行干旱萌发试验与抗性鉴定,筛选不同的抗性材料进行不同程度、不同形式干旱胁迫；确定不同抗性材料萌发出苗的需水阈值及抗性形态指标参数，测定干旱萌发生理指标并寻找干旱胁迫生化响应途径；采用高通量测序方法进行基因表达差异研究，筛选出与油菜抗旱相关的EST。应用生物信息学方法及计算机模型分析上述形态、生理及基因表达数据，从时空变化的角度构建油菜萌发出苗期对干旱胁迫的适应机制。项目研究结果具有重要的科学理论与实践应用意义，不仅有利于油菜抗旱育种和优异基因资源的开发与利用，同时可筛选油菜抗旱萌发的种子处理剂，提出促进干旱萌发的农艺措施，实现油菜大面积抗旱直播全苗。

中国油菜85%的产量来自长江流域，但长江流域秋冬旱频率近年在加大，使得油菜出苗差，生长发育受阻及产量降低。通过系统研究油菜种子萌发及成苗的遗传特性及抗旱机理，对于提高干旱条件下的成苗壮苗率以及最终产量，稳定我国冬油菜种植面积具有非常重要的意义。主要研究结果如下：. 1 油菜苗期抗旱性评价及不同生育期抗旱极端品种鉴定。根据苗期干旱胁迫指数，从645份材料中筛选出了32个抗旱品种和35个干旱敏感品种。140份材料幼苗形态比较发现干旱胁迫使根长和根茎比较对照显著增加，根茎比变异幅度大可作为抗旱评价的重要指标。通过不同生育期干旱比较研究筛选出苗、花期均抗旱的品种2个。花期是鉴定抗旱品种的最敏感时期。.2 萌动的种子和幼苗在干旱胁迫下受到的伤害更大且难于恢复。种子萌发过程中干旱发生时间越早出苗率越低直至不能出苗；恢复正常水分条件后，萌动的种子及播后5d的幼苗更难于恢复，出苗率降低幅度较大。不同时间干旱均使幼苗茎长显著下降，根茎比明显上升；恢复正常水分后，以播种时就开始干旱的幼苗生长最好，以播种后1d开始干旱的幼苗继续生长能力最弱。 .3全基因组关联分析及RNA测序鉴定了油菜抗旱候选基因。 采用25495个Illumina Brassica 60 K SNPs对66个油菜品种进行基因型测定及幼苗生长性状的全基因组关联分析，检测到16个显著关联的位点。选用2个品种进行RNA测序，找出差异表达基因与16个显著关联位点结合鉴定了9个抗旱候选基因。.4 不同抗旱特性品种的脯氨酸含量、电导率及叶温差异明显。生理代谢测定表明，随干旱胁迫程度增加，脯氨酸、丙二醛、电导率增加，抗旱品种增加幅度相对较少。在土壤含水量下降到30%时，生理指标明显上升；下降到20%时，脯氨酸含量增加72-100倍，丙二醛含量增加59-133倍，电导率增加34-579倍。.5 不同外源激素处理对干旱条件下幼苗的生长影响。10种激素3个浓度浸种处理结果表明，赤霉素（1000mg/L）、茉莉酸(50 μM)及褪黑激素(100 μM)在干旱条件下(-0.3 MPa)的成苗率显著高于蒸馏水处理。