Root Characteristics and Drought Resistance of Tibetan Spring Rapeseed（Brassica napus L.）at Bud Stage Under PEG Simulation Drought Stress

【Objective】The study was conducted to understand the effects of drought stress on the root morphology of Tibetan spring rapeseed（Brassica napus L.）and its relationship with drought resistance, and select drought-resistant varieties（lines）of spring rapeseed.【Method】With quartz sand as the substrate, 15%（W/V）PEG solution was used to simulate the drought stress to study the relationship between the root characteristics and drought resistance of Tibetan spring rapeseed at bud stage, and to screen drought-resistant spring rapeseed varieties（lines）.【Results】Drought stress had a greater impact on the relative root weight and relative root-shoot ratio of Tibetan spring rapeseed, and had the least effect on root length. There was no difference in drought resistance between self-breeding materials and those imported from mainland China. Correlation analysis showed that the vitality index indicated an extremely significant positive correlation with relative lateral root number（r2= 0.443*）and relative root length（r2= 0.555*）. Cluster analysis of 28 spring rapeseed varieties（lines）showed that these varieties could be divided into 5 groups at the Euclidean distance of 11, among which, group A had the strongest resistance, with an average relative lateral root number of 69.14, an average relative root length of 96.09%, an average relative root weight of 52.58%, an average relative root-shoot ratio of 63.16%, and an average relative vitality index of 0.59.【Conclusion】The relative lateral root number, relative root length and relative vitality index could be used as drought-resistant identification indicators of spring rapeseed, and other indicators used as auxiliary. In combination of the relative vitality index and cluster analysis, three materials（158106-2, 164046-2, 188013-1）with strongest drought resistance were screened.