Analysis Of Genetic Diversity Of The Clubroot Resistance Germplasms In Brassica Rapa And Molecular Marker-assisted Selection

Brassica rapa crops are cultivated in China. Cabbage clubroot has become one ofmajor crucifer diseases in recent years; its genetic relationship can be figured outthrough the analysis result of the cabbage’s genetic diversity and the clusteringanalysis of the clubroot’s variety and the genetic distance between parents can beascertained so as to distinguish the hybrid vigor. Secondly, researches on the geneticdiversity’s genetic resources are also indispensable materials for cultivating newvarieties of cabbage clubroot. Meanwhile, marker-assisted selective breeding (MAS)shortens the breeding cycle greatly because the molecular marker closely linked withclubroot-resistance can be used to select cabbage’s disease-resistant characters insteadof spending time on inoculation and identification to select disease-resistant singleplants.In the study, PCR amplification is carried out to clubroot-resistant genes oflocated on chromosome A3Y635,Y636and clubroot-resistant genes of located onchromosome A8Y642,Y664by78pairs of InDel and SSR primers; then theamplification bands are detected by8%polyacrylamide gel so as to screen29pairs ofprimers with polymorphism, banding pattern and high stability for establishing theatlas of clustering analysis.Mark50F1populations,1DH lines material and4ECD materials by29pairs ofscreened polymorphic primers according to different genotypes by UPGMA methodin which there are23pairs of SSR and InDel primers whose banding pattern is easiestto judge and52marker sites; then, the dendrogram of55materials is established byNTSYSpc-2.10e clustering analysis software.As a whole,55clustering materials can be divided into classⅠ and Ⅱ. Y635,Y636, Y642and Y664are marked on different chromosomes, from which it is can beconjectured that33clubroot-resistant genes of class Ⅰ may be located onchromosome A3and22of class Ⅱ may be located on chromosome A8.It can be analyzed in the dendrogram that the entire clustering materials can bedivided into5subclasses when the similarity factor is about0.73, in which class Ⅰcontains3subclasses and class Ⅱ contains2. It can also be seen that thepopulation’s classification changes to rise of the similarity factor, reflecting thedistance of the genetic relationship and the difference of the genetic background. Inlight of the classification results, there are rich differences in the genotype and those with special differences can be distinguished from most materials.Screen a pair of polymorphic marked primers out of Y635and Y636andY637and Y639select the homozygous resistance of955single plants from48strainsof Y635,1303single plants from63strains of Y636,1058single plants from45strains of Y637, and432single plants from21strains of Y639which grow up in thefield in the autumn of2013; then, carry out PCR amplification, PAGE gelelectrophoresis detection and statistics of gel electrophoresis, and screen out234single plants with homozygous resistance from Y635,265from Y636,149from Y637and76from Y639respectively.