Application Of SSR Marker On Cabbage Germplasm Genetic Diversity And Purity Identification

Cabbage (Brassica oleracea L.var.capitata.) is widely planted around the world, originated in seacoast of Mediterranean sea and Asia minor. At present, area of cultivation of cabbage reached 900,000 hectares in China.It has been one of important vegetables of China, and it has played important role in annual vegetables supply in China. Through the investigation of Cabbage biological characters and SSR molecular marker, the genetic diversity of 60 cabbage accessions which comed from different contries were revealed. The study on the genetic diversity of cabbage can benefit the collection, identification, conservation, genetic enhancement and effective utilization of conservation cabbage germplasm resource. For proving the genetic relationship among 60 cabbage accessions, to provide reliable theoretical foundation for parents selection and new variety breeding.In addition, the author set up the purity identification system of the cabbage "Xiyuan No 4"by SSR marker.Main study results are as follows:1.11 morphological traits of cabbage was used to cluster analysis,60 germplasm accessions was clustered into 5 groups, at the genetic distance 0.89,2 tip head cabbages were divided individualy from 60 accessions. The analysis showed that accessions in 1,3,4 groups have good consistency,but those accessions in 2,5 groups have small consistency,indiciated cabbage germplasm accessions in the 2,5 groups have relatively great difference.2.22 pairs of polymorphic primers were selected from 95 primers for PCR amplification of the 60 samples of cabbage DNA. It generated a total of 92 clear and repetitive bands,69(75%) of which were polymorphic.Each pair of primer could amplifed 2-6 bands the average amount are 3.14 bands..3. Similarity coefficient, among 60 cabbage materials, was calculated by NTSYS, which ranged from 0.52 to 0.90. A dendrogram was constructed by using UPGMA method,the cluster analysis showed that 60 cabbage germplasms were classified as two groups with the similarity coefficient of 0.58.Frist group consist of 16 cabbage germplasms,which belongs to late maturing and extremely late maturing cabbage materials.the second group has 44 cabbage germplasms,which belongs to extremely early,early and medium maturing cabbage materials.the result is consistent with the division consequence of maturity, it was divided into 13 groups at genetic similarity coefficient 0.70.According to the dendrogram,37 cabbage germplasms from our country were clustered together, this showed that the genetic distance and variability of them is lower.but 23 cabbage germplasms come from overseas were clustered into 8 types,which showed that the germplasms possessed high genetic diversity and a distant genetic relationship. It offers favorable theoretical foundation for parent's selection and new variety breeding in the future.4. Comparing with dendrograms obtained from morphological marker and SSR molecular marker, results of the two markers have great consistency, however, they have certain difference.According to their comparison,we suggest that SSR marker is more reasonable than morphological marker to be available for the genetic diversity study.5. In this study, complementary primers O112-G04 was screened from 95 pairs of SSR primers, The DNA fingerprinting of cabbage "Xi Yuan No.4"was constructed, and the seed purity of cabbage"Xi yuan No.4" was identified. The seed purity was 96.7%, its result is consistent with those obtained in the field test. This result shows that it is reliable to use this pair of SSR primer to identify the purity of cabbage "Xi Yuan No.4".SSR marker was more suitable for cabbage purity identification than morphological characters because of it rapidity, timesaving,labour saving and hard environmental influence.