小麦灌浆期颖果水分运输动态及脱水通路的建立

Grain filling stage of wheat is a key period of water dynamics, water deficit of grouting at this period can lead to serious losses in yield. The wheat harvest season always followed with high temperature and rainy, which can cause high grain moisture and result in spikes germination and mildew. Seed dehydration characteristics can directly affect harvesting time, harvesting efficiency, cost and seed storage safety. Water dynamic balance of filling stage brings great significance to the formation and stability of wheat production. However, water migration path in caryopsis is still unknown, its regulating factors also unclear. This problem become a key bottleneck of theoretical research and crop breeding. We preliminarily detected grouting and the dehydration rate of large area cultivated and high-yield wheat varieties, and we also did anatomy study of nutrient transport organization of wheat caryopsis. On this basis, we use Yangmai16 as test materials; intend to use scanning electron microscopy and transmission electron microscopy combined with micro-CT study, isotope tracer and sample dyeing tracking, transcriptome sequencing technologies to perform researches as follows: (1) Structure and arrange direction of vascular bundles in wheat caryopsis; (2) The water transport pathway in spikelets and caryopsis; (3) The mechanism of water efflux in wheat caryopsis. We intend to preliminary clarify water transport mechanism and dehydration pathway at caryopsis filling stage, to provide theory supports for breeding new varieties of drought-resistant and the high-yielding wheat. This research will also provide new ways for the studies of water dynamics in astomatous fruits.

小麦灌浆期是水分临界期，此时水分亏缺会导致灌浆不足而严重减产；而在高温多雨的小麦收获季节，小麦籽粒水分含量过高又容易造成穗发芽和霉变，籽粒脱水特性直接关系到收获期的早迟、收获效率、成本和安全储存。灌浆期水分的动态平衡对于小麦产量的形成和稳定具有重要意义。但颖果的水分迁移和调控因素仍未知，这已成为小麦高产和育种实践的瓶颈。前期课题组研究过小麦的灌浆和脱水速率，观察过小麦颖果的养分运输组织。在此基础上，本项目拟以扬麦16为试材，运用扫描电镜、透射电镜、micro-CT、同位素示踪、染色剂示踪、转录组测序等技术与方法，研究(1)小麦穗的维管束结构和走向、(2)小穗和颖果中的水分运输路径、(3)颖果中水分外排的机制。研究结果不仅可阐明小麦灌浆期颖果内水分运输机制与脱水路径，并为小麦抗旱抗湿新品种的选育和小麦高产优质栽培提供理论依据，还可为无气孔类果实中水分运转研究开辟新的思路和途径。

阐明灌浆期颖果水分动态和穗部维管束结构，是揭示小麦颖果脱水特性和调控机制的前提。本项目以灌浆和脱水速率显著差异的小麦品种为材料，采用形态解剖技术、光镜和电镜观察、micro CT成像技术和生理指标测定，结合转录组和全基因组基因家族分析，着重研究了灌浆期颖果和穗部水分动态变化、维管束结构及空间走向和灌浆脱水进程的调控因素，取得了以下重要和新颖的结果：.1.探明小麦颖果和穗部维管束发育规律，参试品种间穗轴节片维管束结构无明显差异；颖果背部大维管束在花后10 d基本发育完善，随着颖果灌浆成熟受到挤压变形；扬麦16比对照导管结构完整、内径大且排列规律，更易于颖果多余水分排出。 .2.构建了穗部micro CT扫描数据库，初步探明了小麦穗的维管束结构和走向。茎秆维管束在穗基部节处重新组织并发生分离，分别进入穗轴节片和小穗；进入穗轴节片的维管束在与下一节的连接处重新分配和分离。颖果底部与小花轴之间有一层坚硬结构，对物质和水分进入颖果起隔离和分流作用。.3.不同品种灌浆前中期籽粒含水率接近，快速脱水期含水量下降速率差异明显，并受环境影响，但品种间的差异多年稳定一致。明确颖果与穗部含水率高度正相关，研发了以整穗含水率代替籽粒含水率进行脱水速率测定的方法和脱水性状选择指标并用于育种实践。.4.脱水快早熟的品种扬麦16籽粒中淀粉合成关键酶活性、MeJA含量以及多个LEA基因表达量等指标高于对照扬麦15；与对照相比，扬麦16灌浆中期大量热激蛋白表达上调，花后35 d Raffinose synthase / Sip1表达显著上调。上述指标和基因等可能参与了颖果成熟衰老和脱水进程的调控。.本项目研究结果不仅深化了小麦颖果脱水问题的研究，而且为新品种选育和高产优质栽培提供了理论和方法。发表期刊论文7篇，其中被SCI收录2篇；申请国家发明专利2项；参加学术会议8次，完成了预期目标和任务。

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