| Rapeseed is one of the major oilseed crops in China. Drought is the key environmental factors restricting rapesseed growth and its yield. Breeding for drought-tolerant varieties is one of the most efficient way to alleviate yield reduction caused by drought stress.20 rapeseed cultivars(Brassica napus L.) are studied during germination and seedling stage under drought conditions. The morphological physiological and biochemical characteristics are tested and analyzed. Identification index of drought-resistance during germination and seedling stage have been established preliminary.20 rapeseed cultiwars(Brassica napus L.) are taken as material at germination stage.Different concentrations of PEG-6000(0,5%,10%,15%,20%) are chosen to simulate different drought degrees.The root length, germination length, total length, root/shoot ratio, root fresh weight, germination fresh weight, total fresh weight, root dry weight germination dry weight and total dry weight are measured in simulated drought stress.20% PEG-6000 is the optimum concentration used tosimulate drought stress according to the ten morphological indexes at germination stage. The length and fresh weight reduce significantly and the root/shoot ratio, dry weight rise significantly at germination stage under drought stress simulated by PEG -6000. Relative activities of SOD, CAT and relative content of soluble protein and proline are correlated with physiological and biochemical characteristics total classes of the drought-resistance significantly or very significantly. According to principal components analysis, the relative value of total length, total fresh weight, total dry weight, activity of SOD and proline content can be used as the idrntification indexes of drought-resistance in Brassica napus L.The activities of APX, SOD, POD, CAT and the content of soluble protein and proline rise significantly at 1% level at seedling stage under water stress.The identification indexes of drought resistance are screened by fuzzy multifactoral evaluation summing up the 6 physiological indexes and correlation analysis at seedling stage. The results show that the relative activities of APX, SOD and CAT and relative content of soluble protein have significant influence on drought-resistance and can be used to identify the drought-resistance of rapeseed. By line regression analysis, these 4 indexes are used to consrtuct an equationY=-1.059+0.281 x1+0.776x2+0.112x3 (Y, D value, x, relative activities of APX, x2 relative activities of SOD, x3 relative content of soluble protein).In the experiment, An infrared thermography is employed to measure the variation of seedling leaf temperature of rapeseed under water stress. One efficient approach to enhance rapeseed drought-tolerance is to decrease water loss during leaf transpiration through stoma regulation, which results in the variation of leaf temperature. The results show that under the drought condition, leaf temperature of drought-tolerant lines are higher than that of drought-sensitive line. Under water stress, different leaf temperature can reflect water retentivity and indicate the capability of drought-tolerance indirectly. Under serious drought condition, the percentage of seedling survival of drought-tolerance cultivars 3,4,10,16 which are are higher than that of drought-sensitive cultivars 15 and 20 which ares creened by per-experiment. The results prove that the preliminary appraisal method is feasible for rapeseed drought-resistant identification.Under water stress, the expression level of dehydration-responsive NCED3,CBF3-ADH1,ABA2 gene similarity to Arabidopsis thaliana was up-regulated in Brassica napus L.. Thoese genes may play an important role in response to osmotic stress in B. napus L.. More work should be done to clone drought-resistant related genes and explain the detailed mechanism. |
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