| In this study, we identified and evaluated the drought resistance of9citrus rootstocks such as Citrus reticulata Blanc., Citrus aurantium L cv. Sanhu. Citrus reticulata*Citrus aurantium, Citrus reticulata cv. Chongyi, C.grandis Obseck P. trifoliate.(L) Raf. P.trifoliate (L.) Raf, Citrus aurantium. Ruta "Citrange " cv. Carrizo, Citrus grandis Osbeck by the method of artificial controlling water, combining with drought injury index determining and cluster analysis. In addition, we determined the physiological indexes correlated with drought resistance, namely, water content of leaf, SOD activity. CAT activity, POD activity, MDA content, proline content, solube sugar content and so on. in order to analyze the changing discipline of every physiological index on different rootstock in drought stress and comprehensively evaluate them though factors and membership function analysis so that we could further access the drought resistance of the9citrus rootstocks. Moreover, we analyzed the discrepancy of citrus rootstocks according to the change of physiological and determining of gene expression about SOD、CAT、proline et al in drought stress on the drought resistant and sensitive citrus rootstocks so as to provide the theoretical basis for selection and application of drought resistant rootstock in citrus production and cultivation, which, meanwhile, had significant meaning in improvement and exploitation of germplasm resources on citrus rootstocks. The main results were as follows:1. Though the observation on drought symptoms in drought stress and cluster analysis of drought injury indexes of the9citrus rootstocks, we got the results that the9citrus rootstocks cloud be divided into3types, the first one is the Citrus reticulata Blanc. and Citrus aurantium which had best drought resistance; the second one is Citrus aurantium L cv. Sanhu, Citrus reticulata cv. Chongyi, C.grandis Obseck P. trifoliate.(L) Raf, P.trifoliate (L.) Raf, Ruta "Citrange" cv. Carrizo which had the better drought resistance than the third one consisted by Citrus reticulataxCitrus aurantium and Citrus grandis Osbeck.2. The results of physiological indexes analysis of the9citrus rootstocks from factors analysis and membership function method showed that there were relativity in water content of leaf, SOD, CAT, POD, MDA, proline and soluble sugar content, so we could not judge the drought resistance by one index and the order of drought resistance in the9citrus rootstocks was Citrus reticulata Blanc> Citrus aurantium> Ruta "Citrange" cv. Carrizo> Citrus aurantium L cv. Sanhu> P.trifoliate (L.) Raf> C.grandis Obseck P. trifoliate,(L) Raf> Citrus reticulata cv. Chongyi> Citrus reticulata×Citrus aurantium> Citrus grandis Osbeck. Citrus reticulata Blanc is a local resource, which possessed exploiting potential in drought resistant rootstock. 3. From the physiological indexes change of different citrus rootstocks in drought stress, we could see that the related water content dropped gradually with the drought stress aggravation; SOD had the trend of up-down, CAT was up-down-up, POD changed by different varieties, but the SOD. CAT and POD of different citrus rootstocks held function of coordination and strengthen in each other for drought resisting; the change of MDA content corresponded with the activity of SOD, CAT and POD in some extent and the Citrus reticulata Blanc which had strong drought resistance held low value and little vary; proline content grew up with the drought stress aggravation and the soluble sugar content of ds-15d excelled CK, which showed the growth of proline and soluble sugar content was good for increasing of drought resistance.4. The analysis of gene expression of SOD, CAT, proline et al.in drought stress from Citrus reticulata Blanc and Citrus grandis Osbeck indicated that the genes of sod, cat, p5cs and lea of Citrus grandis Osbeck expressed down in ds-5d and up in ds-10d and ds-15d; Citrus reticulata Blanc had not discrepancy between ds-5d and Ck, but declined in ds-10d and ds-15d. And according to the result of the discussion in change of related physiological indexes that suitable drought was beneficial to crop growing and Citrus grandis Osbeck adapted in ds-5d, Citrus reticulata Blanc was in ds-10d to ds-15d, we concluded that the genes expression of sod, cat. p5cs and lea went down in fitted drought condition but went up in drought stress, which were the raising expression genes in inducement and the discrepancy of gene expression matched with the change of physiological indexes. |
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