新疆早实核桃主栽品种坚果种仁油脂亏缺成因及其机理研究

With the characteristic of precious，thin shell thickness and high yield of Xinjiang walnut，it is the predominant industry in Tarim Basin regions and has become mainly farmer's economic income source. The cell of kernel has full of oil bodys and the content of fat is about 60%.But with the expansion of cultivated area,the quality of walnut was declining.After our investigation,the percentage of nut with kernel oilness was about 10%.It is not clear that what cause the kernel with oilness and how does this factor influence the kernel development without oilbodys.Because the problem are unknown,three hypothesis are puts forward to find out the cause and mechanism of walnut kernel oilness in this project and several approaches are used to gain insight into the extent and cause of this phenomenon.The oilbody anabolic don't start which lead to the kernel oilness of walnut.The lack of nutrients or the lack of genes which affect the oilbody anabolic,and make the phenomenon of kernel oilness. The methods of pollination experiment, carbohydrate supply test and RNA-seq technology are used to test three hypothesis.By the results of these rearch,we want to explore the cause and occurrence mechanism of precocious walnut cultivars kernel necrosis.The purpose of this study is to comprehensive understand the reason which makes walnut kernel oilness occurrence and can provide theoretic basis for yield of walnut, which is essential for the development of walnut in Xinjiang.

核桃坚果"无仁或种仁皱缩"表现为种仁油脂亏缺。以种仁油脂亏缺为特征的种仁发育异常坚果在南疆盆地新疆早实核桃主栽品种坚果中所占比率高达10%以上，已严重影响到新疆南疆核桃主产区核桃坚果的品质和单位面积的经济效益。但造成核桃坚果种仁油脂亏缺的成因及种仁油脂亏缺的油脂代谢形成机制尚不清楚。为此本项目以新疆早实核桃主栽品种'新温185号'和'新新2号'为研究对象，以种仁油脂合成代谢为线索，采用人工授粉、树冠等体积分隔、去叶减源、高通量RNA测序等技术，通过人工控制性试验和分子生物学方法，检验核桃种仁油脂亏缺成因，即油脂合成代谢未启动、油脂合成代谢物质供应不足和油脂合成代谢过程中因酶（基因）缺失或异常的假设，阐明核桃种仁油脂亏缺与生殖过程、碳水化合物供给和种仁发育中酶类（基因）缺失或异常之间的关系，揭示种仁油脂亏缺的油脂代谢形成机制，以期为新疆早实核桃主栽品种的优质丰产栽培提供科学依据和技术途径。

项目针对新疆核桃产业发展中的核桃坚果“无仁或种仁皱缩”这一生产实际问题，提出核桃种仁油脂亏缺与油脂合成代谢未启动、碳水化合物供应不足和酶类缺失/缺少有关。基于这一假设，项目以新疆主栽品种‘新新2号’和‘温185’为试材，从授粉受精实验，碳水化合物供应实验，发育正常和种仁油脂亏缺的种仁的高通量测序对比实验等方面进行研究，结果表明：（1）核桃花粉生活力不高与核桃小孢子母细胞减数分裂过程中的二分体和四分体内存在微核和多数花粉粒内部无细胞核有关。（2）花粉在柱头上的萌发始于授粉后 8 h ，144 h 后花粉管到达子房腔，172 h 后花粉管伸到隔膜顶端，240 h 后人工辅助异花授粉的雌雄配子形成受精核；此时其他授粉方式下的花粉管生长才到达胚囊位置。（3）不同授粉方式下核桃胚、果实的发育时期基本一致。未受精的卵细胞经过数次分裂产生多细胞原胚，发育形成成熟的果实。但在雌配子形成期、2 细胞原胚期、球形期或者产生游离胚乳核的时期均可发现种室内空胚囊腔，其中以孤雌生殖比例最高。（4）疏散分层形核桃冠内不同层次部位的叶面积指数与之相应位置的透光率呈负幂指数关系，符合Beer-Lambert模型定律。冠内外部和上层叶面积指数最小和透光率最大区域的坚果产量最高，核桃物理化学品质格局变化与冠内光分布特征呈正相关。（5）初步得出叶果比会影响叶片中的叶绿素含量和净光合速率而影响到果实发育进程和产量，尤其是当叶果比值较小时，核桃种仁会出现油脂亏缺。（6）通过对比饱满种仁与不饱满种仁的高通量测序结果，最终获得脂肪酸合成代谢相关的基因 14 条，甘油磷脂合成代谢相关的基因 30 条。accB、accA、accD、FabD、FabG、CDS1等几个关键基因均呈上调表达，若这些基因缺失，不利于核桃果实的生长发育和油脂合成。上述研究发现了核桃种仁油脂亏缺的成因，初步揭示了核桃种仁油脂亏缺的机理，为新疆早实核桃主栽品种的优质丰产栽培提供了一定地科学依据和技术途径。