Development And Application Of EST-SSR Markers In Radish(Raphanus Sativus L.)

Radish is an important vegetable crop in China. The fundamental research of radish molecularbiology falls behind other vegetable crops and can not meet the need of radish breeding. The source ofradish germplasm is abundance, but the phenotypic character and genetic background of cultivars radishis similar and narrow. We downloaded the radish EST resources from NCBI to develop the radishEST-SSR markers and used the markers analyzing the75main radish cultivars’ genetic diversity. Andwe used10radish EST-SSR markers construct the radish core collection. The main results were asfollows:1、A total of287349ESTs of radish were downloaded from NCBI database. After preprocessing,58105non-redundant ESTs with the total length of38622.476kb were obtained. By using the MISAprogram, a total of3718SSRs were observed in3523ESTs and the average distance between SSRs was10.39kp.265types of motifs were found in radish s ESTs and the dominant motifs types aredinucleotide, trinucleotide and exanucleotide repeats. AG/CT was the main motifs type（91.34%）indinucleotide repeats; AAG/CTT was the main motifs type （35.86%） in trinucleotide;AAGGAG/CCTCTT and AAGAGG/CCTTCT were two main motifs types （total12.78%） inexanucleotide. Using the Primer3.0,183primers were designed and synthesized based on differentdominant motifs types, and verified with12typical radish germplasm for polymorphism and one pair ofparents and their F1for codominance. The results showed that the products of159primers were clearand effective，64pairs were polymorphic among the germplasm and27were codominant between theparents and their hybrids.2、By analyzing the genetic relationship of75main radish cultivars from market by55pair highpolymorphism EST-SSR markers,it was found that the average numbers of alleles, the average effectivenumbers of alleles and the average of genetic diversity information index in these75main radishcultivars were all not high. It demonstrated that the level of these75main radish cultivars geneticdiversity was lower and the genetic similarity was higher. The genetic background of these cultivarsmay rather narrow. The similarity coefficient was1.00among the radish cultivars of white fleshy rootwhich came from Korea named Chenxiao and Xuefenghuang; Futianchun, Hanyuchun, Shengxuechun, Tianhongshangpin, Huaqiangchun, Shengtianchun and Xueguan; Chaojibaiyu, Xuelongwang and Hanbailong; Chunbaiyu and Baiyuchun respectively. It suggested that thegenetic relationship between these cultivars was closer. The molecular identification codes of75mainradish cultivars were made by using11pairs of specific core primers and the definite coding regulation.This is a base for protecting the intellectual property and realizing the quality control of the seeds onmarket.3、10pairs clear, effective and high polymorphism EST-SSRs were used for identifying the2871radish germplasm. The number of alleles, effective number of alleles and Shanon s information indexwere employed to compare three core collections constructed by three methods and sampling proportion.It was found the progressively compression clustering and rare alleles priority selecting method and the proportion of10%were the best. Finally,294accssions of germplasm were selected into the radish corecollection. Its genetic structure and genetic relationship had been analyzed.The results of study not only can provide the technology supporting of radish molecular breedingbut also can provide the theory of radish breeding and parent selection in fundamental research, it willpromote the radish germplasm resources have better application in future.