| Early bolting is the main factor affecting the production of radish in winter and spring.Based on the genetic diversity analysis of phenotypic traits of 73 radish materials and the evaluation of bolting resistance in field,bolting resistance germplasm was screened and the correlations among the bolting resistance,agronomic traits in field,and the change of physiological and biochemical indexes before and after bolting were analyzed.Meanwhile,the differences in gene expression levels related to the flowering of radish bolting were studied in order to provide theoretical references for the radish bolting resistant germplasm resource innovation,the breeding of new varieties of radish and the study on the mechanism of bolting resistance.The main results were as follows:1.Identification of bolting-resistant of radish germplasm resources and its relationship with phenotypic traits.Based on 8 bolting-resistance indexes,and by using the method of cluster analysis and membership function appraisal,the bolting resistance of 73 radish materials were identified.The results showed that the clustering analysis method and subordinate function respectively the radish bolting resistance strength of the material properties classified into 3 classes and class 5,the least bolting resistance germplasm New Zealand short-leaf No.13 radish and the most bolting resistance germplasm South Korea’s big root were screened.The self-developed radish materials of W2(14)-18-3 hy15-2-2-1,W3(14)-13-4 xht13-1-1-1 from the college of agriculture of guizhou university belonged to bolt-resistant germplasm materials,which could be comparable to South Korea’s big root.The correlation analysis between phenotypic traits and bolting resistance of different radish materials showed that the leaf type,leaf shape,leaf color,leaf margin,leaf nick,root length,root thickness,root weight and bolting resistance were significantly positive correlation.The smoothness,upper skin color,skin color,root color and root type were significantly negatively correlated with the resistance to bolting.There was a significant negative correlation between leaf vein color and bolting resistance.There was no significant correlation between leaf tip traits,leaf bristles,leaf length,leaf width,and root distribution of fleshy roots.The gray correlation analysis of bolting resistance and phenotypic traits showed that the correlation between the bolting resistance and five out 19 phenotypic traits,including root traits,root weight,leaf shape,leaf margin and root length was most significant,suggesting that these five phenotypic traits have the highest correlation with bolting resistance.2.The correlation analysis between radish resistance and physiological and biochemical traits.In this experiment,the changes of physiological indexes,including soluble sugar,soluble protein content,and changes in superoxide dismutase(SOD),peroxidase(POD)and catalase(CAT)activities,before and after bolting in 20 materials were analyzed.The results showed that the soluble sugar content of most radish materials increased significantly after bolting,reaching the highest at budding stage and thereafter.Along with the bolting process gradually declines,the minimum level is above 5 cm.The trend of superoxide dismutase(SOD)activity is not much different,but the highest level of SOD activity is associated with different bolting resistance.POD activity of 20 radish varieties increased first before and after bolting,reaching the highest at 1-2 cm,and then gradually decreased with the bolting process,and returned to the level before bolting longer than5 cm.CAT activity in all materials showed a significant decrease after bolting.The change of these characteristics are associated with the bolting process,increasing gradually before bolting,then declining to lower level after bolting.3.Changes of gene expression related to bolting and flowering of radish.The results showed that bolting tolerance and late flowering traits were positively correlated with the expression of two flowering inhibitory genes(FLC1.1 and FLC1.2).The expression of FLC1.1 gene in Korean Daikon was significantly higher than that in New Zealand short leaf 13,which was easy to bolting.When radish entered flower bud differentiation stage and bud stage,the expression of FLC1.1 was relatively lower.In three different stages and different tissues,the expression level of FLC1.2 gene in Korean Daikon root of bolting-resistant material was significantly higher than that of New Zealand short-leaf 13,which was easy to bolting.The expression of VRN1 and VRN2 genes were positively correlated with flowering and bolting traits,and the expression levels of VRN1 and VRN2 genes were highly expressed in shoot tip and root at undifferentiated stage of flower bud,and there was a positive correlation between the expression of VRN1 and flowering and bolting traits,and the expression level of VRN2 and VRN1 genes in shoot tip and root during the undifferentiated stage of flower bud.Moreover,the expression levels of VRN1 and VRN2 in New Zealand short Leaf 13 were slightly higher than those in Korean Daikon during flower bud differentiation.At bud stage,the expression of SOC1 gene in the leaves of New Zealand short leaf No.13 was significantly higher than that of Korean Daikon,and the expression of SOC1 gene was positively correlated with flowering in the early stage of flower bud differentiation,and the expression of SOC1 gene decreased at all three stages along with the time,and the expression level of SOC1 gene in short leaf was significantly higher than that in Korean Daikon.Only in the shoot tip of New Zealand short leaf No.13 at the undifferentiated stage of flower bud,it was significantly higher than that of Korean Daikon,but in leaf,Korean Daikon was slightly higher than New Zealand short leaf 13;At the flower bud differentiation stage,the expression level of SOC1 gene in Korean Daikon was higher than that in New Zealand short leaf 13 in root and stem tip,and at the bud stage and stem tip of Korean Daikon,the expression of SOC1 gene was higher than that in New Zealand short leaf 13. |
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