Screenning Of Waterlogging Tolerant Rapeseed Germplasm And Analysis Of The Tolerance Mechanism

Rapeseed is the largest oil crop in China.As the main oil crop producing area in the Yangtze River basin,the annual planting area and total output exceed 90% of the country."Rice-rapeseed" rotation is an important way of rapeseed planting in the Yangtze River Basin.Therefore,rapeseed is prone to waterlogging stress caused by soil compaction and poor drainage during growth and development,and the frequent precipitation caused by climate change increases the risk of rapeseed being waterlogged.The growth and development of rapeseed are inhibited or even killed in the seedling stage,which leads to the yield loss in the later stage and seriously affects the production of rapeseed.Therefore,it is of great significance to select stain tolerance germplasm and breed stain tolerance varieties to ensure the production of rapeseed.However,the physiological characteristics and genetic mechanism of stain tolerance in rapeseed are still unclear,which limits the progress of breeding.In this study,706 backbone parents,stable inbred lines and representative domestic and foreign conventional varieties of Brassica napus L.were used as materials.After waterlogging treatment at germination stage,the survival rate of seedlings was measured,and extreme differences in water tolerance and water sensitivity genotypes were screened,and the physiological responses of the two groups of materials after flooding were compared and analyzed.The transcriptome data of 24 h waterlogged were compared to explore the main gene regulatory networks and metabolic pathways of the formation of stain tolerance.The test results are as follows:1.Based on the previous methods,the method for screening the stain tolerance of rapeseed was modified and established.The survival rate after 6 days of full flooding at germination stage and 3 days after dewatering was used as the screening index of rapeseed stain tolerance.This method was used to screen and evaluate the stain tolerance of 706 rapeseed resources,and 706 rapeseed resources were divided into highly waterloggingtolerance,waterlogging-tolerance,lowly waterlogging-tolerance,poorly waterloggingtolerance and waterlogging-sensitive.There were 57 highly waterlogging-tolerance materials,278 waterlogging-tolerance materials,168 lowly waterlogging-tolerance materials,94 poorly waterlogging-tolerance materials and 109 waterlogging-sensitive materials,indicating that there was a rich genetic diversity in stain tolerance of rapeseed.2.Five stain tolerance genotypes and five stain sensitive genotypes were selected as experimental materials to compare the physiological responses of different genotypes under waterlogging stress.After 5 days of waterlogging in three leaf stage,the activities of SOD and POD were increased in the stain tolerance genotypes,and the increase of SOD activity was higher than that in the sensitive stain genotypes,while the activity of CAT was decreased.The activities of SOD and CAT were increased in the sensitive stain genotypes,but the increase of SOD activity was small,and the activity of POD was decreased.The decrease range of MDA accumulation and chlorophyll content in the stain tolerance genotype was smaller than that in the sensitive stain genotype,while the increase range of soluble protein content was higher than that in the sensitive stain genotype.3.Transcriptome analysis was performed on 5 stain tolerance genotypes and 5 stain sensitive genotypes,which were cultured normally and treated with water stress for 24 h.The results showed that a total of 8584 differentially expressed genes were detected between the stain tolerance genotype and its control after waterlogging stress,including 5072 up-regulated genes and 3512 down-regulated genes.There were 8952 differentially expressed genes between rapeseed sensitive genotypes under waterlogging stress,including 5063 up-regulated genes and 3889 down-regulated genes.GO enrichment analysis of these differentially expressed genes showed that more differentially expressed genes were enriched in membrane,cell,cell part,binding protein and catalytic activity.KEGG enrichment analysis showed that common differentially expressed genes between the tolerance and sensitive stain genotypes and their respective controls were significantly enriched in circadian rhythm-plant,tryptophan metabolism,porphyrin and chlorophyll metabolism and other pathways.KEGG enrichment of specific differentially expressed genes between the two groups of the stain tolerance and sensitive genotypes and their respective controls.The stain tolerance genotypes were significantly enriched in carbon metabolism,phenylpropanoid biosynthesis,biosynthesis of amino acid and other pathways.The sensitive genotypes were significantly enriched in plant hormone signal transduction,sucrose and starch metabolism,vitamin B6 metabolism and other pathways.At the same time,some key transcription factors,such as AP2/ERF,b HLH,MYB,WRKY and NAC,were also screened to play an important role in rape response to flooding stress.