【作者】 王士强；

【导师】 胡银岗；

【作者基本信息】 西北农林科技大学 ， 遗传学， 2008， 硕士

【摘要】 水资源短缺是目前全球性的焦点问题之一。在世界范围内干旱频繁发生,全球性缺水问题日趋尖锐,干旱对作物生产造成的影响越来越大,干旱缺水已经成为世界农业生产面临的严重问题。小麦是中国仅次于水稻的第二大粮食作物,在我国粮食生产中占有举足轻重的地位。但是,长期以来由于干旱和水资源短缺的制约导致我国小麦产量低而不稳,一直徘徊不前。然而,到目前为止还没有形成一套准确、可靠、简单、统一的鉴定方法和指标体系。因此,研究小麦的抗旱性鉴定指标,提高抗旱性鉴定与选择的准确性,并结合分子生物学的技术进行抗旱候选基因的功能鉴定对于选育小麦抗旱新品种,促进粮食生产的持续稳定发展有着非常重要的作用。本研究应用灰色系统理论对不同小麦品种相关抗旱性鉴定指标进行了筛选;并克隆了甲硫氨酸循环中的关键基因S-腺苷甲硫氨酸合成酶基因,初步分析了其和抗旱性的关系,得到如下结论:1.采用灰色系统理论中灰色关联分析方法对分别种植于干旱棚和大田自然降水两个条件下的65个小麦品种的主要农艺性状和部分生理生化性状与其抗旱指数的关联度进行分析和评价,确定了各性状与抗旱指数的关联度。依次为:气孔导度(0.7995)、光合速率(0.7909)、蒸腾速率(0.7556)、可溶性糖含量(0.7467)、丙二醛(MDA)含量(0.7336)、游离脯氨酸含量(0.7267)、穗长(0.7102)、穗粒数(0.7095)、千粒重(0.7005)、水势(0.6959)、有效分蘖数(0.6951)和株高(0.6866)。与抗旱指数关联度最大的是和叶片气孔相关的生理生化性状,它们在作物受到干旱胁迫时所受的影响最大,与作物抗旱性关系最为密切。因而可以选用气孔导度、光合速率和蒸腾速率等生理生化性状进行小麦抗旱性的以性状为基础的选择,以提高选择效率。2.在计算所得加权抗旱指数的基础上,对参试品种进行聚类分析,其中NC223、晋麦47、小偃6号、陕麦168、西农4504、宁春27、洛旱6号和农大优麦2号等品种的抗旱性较好,其加权抗旱指数均达到了1.2000以上。聚类结果基本可以反映这些品种的选育和利用区域,表明这些品种是与所选育和利用地区的干旱条件相适应的,也说明计算所得到的各品种的加权抗旱指数可以较好地反映各品种本身的抗旱特性。3.在上述聚类分析的基础上,以NC223、小偃6号、小偃22、沧6003、烟D27、中国春和洛旱6号为材料,应用同源克隆和RACE技术克隆了S-腺苷甲硫氨酸合成酶基因,得到其全长cDNA序列,共计1420 bp。用中国春的序列进行序列分析发现该基因编码396个氨基酸,含有3个相对保守的结构域(N端、C端和中间结构域)。并将其氨基酸序列与大麦、水稻和一粒小麦上已经克隆的该基因编码的氨基酸序列进行比较,发现其同源性分别为100 %、84 %和45 %,说明其和大麦的亲缘关系最近。并对这7个材料进行了比较,发现仅有少数单碱基的变异。4.在克隆所得该基因序列的基础上,应用BSMV-VIGS技术以NC223为材料对该基因进行沉默,初步分析了其和抗旱性的关系。从沉默结果看,沉默植株经干旱胁迫后较正常植株在形态上有明显的变化(其下部叶片变黄),说明沉默植株更易受干旱胁迫的影响,从而初步确定了S-腺苷甲硫氨酸合成酶基因和抗旱性的关系。更多还原

【Abstract】 Water shortage is one of the focuses all over the world. Water shortage is becoming more serious and its influence on crop production is also becoming greater due to the frequent happening of drought, therefore, Drought has become the serious problem to the world agriculture production.Wheat is the second staple crop after rice, and has very important role in the national food production. However, the yield of wheat is low and precarious in the world for a very long time because of drought and water shortage, and remains behind. But, a set of accurate, stable, simple and systematic method and index system for drought-resistance identification and selection is still underdevelopment. Hence, it is of very important role to study the indexes for identification of drought-resistance and candidate genes for the selection and improvement of drought-resistant cultivars, which can greatly enhance wheat food production in the world. Gray system theory was employed in this study to select indexes for the drought-resistance identification in different wheat cultivars; the gene of s-adenosylmethionine synthetase was cloned, and the relation to drought resistance was preliminarily analysed. The results are as follows:1. The method of gray relational analysis in gray system theory was used to identify the correlation between drought resistance and indexes including agronomical traits and physi-biochemical indexes. Gray correlation degrees were calculated between each trait and its drought tolerance index, they were ranked according to their gray correlation degree to drought tolerance as follows: stomatal conductance (0.7995), photosynthetic rate (0.7909), transpiration rate (0.7556), soluble sugar content (0.7467), MDA content (0.7336), dissociative proline content (0.7267), spike length (0.7102), number of kernel per spike (0.7095), 1000-kernel weight (0.7005), water potential (0.6959), effective tiller number (0.6951), plant height (0.6866). the physi-biochemical traits related to leaf stomatal have the closest relationship with the drought tolerance of wheat, and these traits were significantly influenced by water stress, thus had the greatest relation degree with drought-tolerance index. So the physi-biochemical traits including stomata conductance, photosynthetic rate and transpiration rate could be used in the trait-based selection of drought tolerance to improve the selection efficiency.2. All the cultivars tested were clustered based on the weighted drought-tolerance index, among which the cultivars Luohan 6, Xiaoyan 6, Jinmai 47, Shanmai 168, NC223, ning chun 27, xi nong 4504 and nong da you mai 2 have very well performance, and all of their weighted drought-tolerance indexes are above 1.2000. the results could well represent their bred and applied areas, and also indicated that the weighted drought-tolerance index could well represent the intrinsic drought-resistant ability.3. Homocloning and RACE methods were used to clone the gene of s-adenosylmethionine synthetase from the cultivars NC223, xiao yan 6, xiao yan 22-3, cang 6003, yan D27, Chinese spring and luo han 6, based on the cluster result. The whole cDNA sequence is 1420bp long. Sequence analysis based on the sequence of Chinese spring indicates that it encodes 396 amino acids, and contains 3 relatively conservative domains (N terminal, C terminal and middle domain). Sequence alignment based on the barley, rice and einkorn show that their homogeneities are 100%, 84% and 45% respectively, indicating the closest relationship with barley. And the sequence alignment between the 7 cultivars shows that there are only few single nucleotides mutations.4. BSMV-VIGS technique was used to silence the gene based on the sequence of NC223 in order to determine its relationship with drought resistance. The result show that the silenced wheat plant is different from the control one concerning the morphological trait (bottom leaves turned yellow), which implies that the silenced plant is more vulnerable to drought stress, so the preliminary relationship of gene of s-adenosylmethionine synthetase with drought resistance is determined.更多还原