| The threat of drought to agriculture production is a worldwide problem. Especially the drought becomes more and more serious due to environmental degradation in recent years, and it has become one of the limiting factors of crop yield all over the world, so the experts of the world pay more and more attention to the study of abiotic stresses such as drought.Cassava(Manihot esculenta Crantz) which is grown mainly in tropical and subtropical regions, is one of the three tuber crops in the world, and it is mainly used for feed, food and industrial raw materials. Cassava has strong ability to resist drought and barren, but because the growing areas of cassava encounter drought becoming more and more serious, so the drought-resistant cassava varieties are demanded increasingly. But a detailed method and index system for drought-resistance identification and selection is still underdevelopment. Hence, studying the indices for identification of drought-resistance, is a certain guiding significance for selection and improvement of new drought-resistant cassava varieties.In this study,8physi-biochemical indices were measured in17cassava cultivars grown at well-watered and drought-stressed conditions,8physi-biochemical traits and cassava varieties were selected using gray relational grade analysis method; The method of proteomics was applied to this research. In order to investigate the biological function of special proteins, the proteome of cassava leaves that collected from well-watered and drought-stressed plants were studied. The main results of this study are as follows:1. The method of gray relational analysis in gray system theory was used to identify the correlation between physi-biochemical traits and drought tolerance index of cassava, and the traits’gray correlation degrees to drought tolerance were ranked as follows:photosynthetic rate(0.8838), chlorophyll content(0.8744), soluble protein content(0.8129), MDA(0.7995), relative electrolyte leakage rate(0.7440), soluble sugar content(0.7369), SOD(0.7015), dissociative proline content(0.6271). The closest relationship with drought tolerance were photosynthetic rate, chlorophyll content and soluble protein content, and these traits were significantly influenced by water stress, thus had the greatest relation degree with drought-tolerance index. So they could be used on selection of drought tolerance to improve the selection efficiency.2. The weighted drought-tolerance indices of all cassava varieties were tested based on the correlation degree between physi-biochemical traits and drought tolerance index, then the drought-resistant ability of cassava varieties was ranked from strong to weak.7physi-biochemical indices(the correlation degree was lager than0.7000) were chose, and based on the weighted drought-tolerance index of these physi-biochemical indices,17cassava varieties were divided into different categories according to cluster analysis. There was a good agreement between the the results of cluster analysis and gray relational analysis on dividing the cassava varieties into different drought-resistant types. After the two analysis results, SC124, SC8, SC5had the strongest drought tolerance; while GR911, C1115, SC6068had the weakest drought tolerance among the17cassava varieties.3. Two-dimensional electrophoresis was used to produce the leaf protein images of well-watered and drought-stressed SC124seedling stage, based on the selection of drought-resistant cassava varieties. The Delta2D software was used to analyse the proteins associated with drought.43differential protein spots were found from2-DE images, including40up-regulated protein spots and3down-regulated protein spots; of which23protein spots were identified using the mass spectrometry (MALDI-TOF-TOF-MS/MS) identification technology and the NCBInr database, they were all up-regulated protein spots. These23proteins were classified according to their function, in which2proteins were associated with photosynthesis;5proteins were associated with carbohydrate and energy metabolism;2proteins were associated with detoxifying and antioxidant;1protein was associated with protein biosynthesis;2proteins were associated with chaperones;3proteins were associated with HCN metabolism;1protein was associated with structure;7proteins were function unknown proteins. The results showed that it was to be adjusted the maintenance of photosynthesis, energy metabolism, HCN metabolism and enhanced its detoxifying and antioxidant to resist drought in cassava plants under drought stress. |
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