Preliminary Screening Of Waterlogging Tolerant Rapeseed Resources And Genetic Diversity Analysis Based On SSR Markers

A preliminary evaluation was made on waterlogging tolerance in 176 accessions of rapeseed stock materials with the method of germinating seeds under submerging treatment. The rapeseed materials included three species:Brassica. napus L., Brassica. rapa L., Brassica. juncea L. The B.napus lines were mainly from Southwest China, with some from abroad. Waterlogging tolerance was compared and ordered among these materials.based on the subordinate value. Field experiments were carried out for further investigations on the waterlogging tolerance of 20 rapeseed materials selected from the 176 accessions. Genetic diversity was examined with 65 rapeseed varieties differing in waterlogging tolerance by SSR markers. The following important results were obtained in the experiments:Anoxic treatment of germinated rapeseed seeds showed:seedlings growth was repressed badly by anoxic treatment, roots was the worst affected part, and fresh weight came second; difference of waterlogging tolerance among rapeseed varieties were obvious, genetic variation of rapeseed varieties were abundant, coefficient of variation ranged from 22.64%-56.21%, the value of RVI came first; relative analysis indicated that very significant or significant correlation existed between 6 indexes, very significant positive correlation showed between RVI and relative seedlings rate, relative root length, relative seedling length, relative fresh weight, very significant negative correlation showed between RVI and conductivity, very significant negative correlation showed between conductivity and relative seedlings rate, relative seedlings length, significant negative correlation showed between conductivity and relative root length, relative fresh weight; according to principle component analysis, seedling vigor factor, seedling recovery growth factor and membrane stability factor were selected, the above three PCs account for 88.34% of total variation; average subordinate value can integrate information of 6 indexes, we ordered waterlogging tolerance of rapeseed varieties based on subordinate value, and selected some extreme materials; at genetic distance 5.86, cluster analysis divided 176 rapeseed varieties into four groups, each of them represent different waterlogging tolerance type.Field waterlogging treatment indicated that plant growth were repressed seriously, compared with control, root length, plant height, plant shoot fresh weight, root fresh weight, root/shoot ratio were decreased by various degree, plant dry weight were affected terribly; relative analysis suggested that very significant, significant or insignificant correlation showed between indexes; abundant genetic variation showed in 8 indexes, ranged from 8.43%-30.94%, correlation index of relative root fresh weight and relative root length came first and last, respectively; component analysis selected 3 principle components which account for 90.38%of variation, they were morphogenesis factor, plant height factor and water absorption factor.For physiological indexes, after field waterlogging treatment, Chlorophyll content, water content were decreased, MDA content, soluble protein content, Pro content, SOD enzyme activity increased, range of MDA content came first, but range of water content came last; correlation showed between 7 indexes; abundant genetic variation showed in 7 indexes, ranged from 2.50%-69.96%, correlation index of MDA content and water content came first and last, respectively; principle component analysis selected 5 principle components, which account for 88.77%of total variation, they were named water and photosynthesis factor, adversity and photosynthesis factor, inclusions factor, antioxidant enzymes factor and adversity factor.SSR analysis showed that 40 SSR markers tested 438 identical gene variation, number of identical gene ranged from 4-30, each primer amplify 10.95 locus in average, PIC were covered from 0.65-0.96, average PIC was 0.84; cluster analysis showed that rapeseed varieties can be divided into 4 groups, each group represent different waterlogging tolerance type.