| 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. |
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