Study On Genetic Relationships Among Radish And Its Relatives In Brassica And Genetic Linkage Map Construction In Raphanus

Radish (Raphanus sativus L.) is an important commercial vegetable, China is the mainplace where radish was origined and domesticated, and has abundant germplasm. Wellutilizating the germplasm and selection of parents for hybridization and improve the cropare the important objectives in plant-breeding programs. Research on genetic relationshipand linkage map construction is meaningful for enhancing breeding efficiency anddeveloping breeding program. In this research, RAMP maker were firstly employed toestimated genetic diversity among Raphanus and discussed the pedigree relationshipsamong Raphanus and Brassica. RAPD marker were employed to analyse the genomic ofparents, their hybrids and F₂ progenies in radish, and a genetic map of the Raphanus wasdeveloped based on F₂ population of inter-subspecies hybrid, using RAPD, ISSR andRAMP markers. It provided a basic for radish molacular breeding and QTL mapping.Genetic diversity and relationships among 17 varieties from Raphanus and 11 accessionsfrom Brassic were evaluated with RAMP markers. The 35 RAMP primer combinationsgenerated 626 bands, of which 618(98.7ï¼…) were polymorphic, with 17.7 polymorphicbands on average. Result of cluster analysis (UPGMA) was consistent with that principalcoordinate analysis (PCA) using NTSYS-pc software. Brassica species was distinguishedfrom Raphanus, but the similarity coefficient value was high. There was considerableRAMP variation among Raphanus, five primer combinations could clearly distinguish the17 radish accessions, respectively. The varieties of radish could be grouped according to thegeographical origin and the root color. In Brassica, the species with B genome wereseparated from those with the A and C genome, which indicated that the geneticrelationships between different species in Brassica were correlated with their genomes. Inaddition, compared with other radish varieties, the two radish specise, 'Heisen' (R. sativusL. var niger) and 'Lanhuazi' (R. sativus L. var raphanistroid) were much closer to Brassicaaccessions. Again, the hypothesis that Raphanus was derived from a hybridization betweenthe rapa/oleracea and the nigra lineages also could be supported. These results suggestedthat the RAMP markers could be used as an effective method for fingerprinting andvarieties evaluating the genetic relationships among genera or species in Brassicaceae. RAPD marker were used to study parents and their hybrids in radish. Of 463 primers,Seventy primers were selected, the polymorphic bands ranged from 26.1ï¼…to 31.0ï¼…, perprimer could amplify 1.95～2.37 polymorphic bands on average, with the lowerpolymorphism. Differences were amplyfied from obverse cross and inverse cross, most ofloci come from their maternal genome, and 31.1ï¼…loci come from paternal genome, maybethe locus was easily express in the hybrids. Twenty-four primers weye used to amplified 28genomic DNA of F₂ population of Nau-WH-04×Lanhuazi, among thirty-four RAPDmarker-loci, four marker-loci were not segregated and one marker-locus was un-inheritedin F₂ population. The ratio of the marker-loci segregation was tested with aχ²-test,twenty-five out of twenty-four marker loci displayed nomal Medelian segregation althoughfour maker loci were distorted from the expected 3:1 ratio in the F₂ population, thissuggested that RAPD marker was mainly nomal segregated among F₂ population of radish.It shown that RAPD marker could be employed to construct genetic linkage map using thisF₂ population.A genetic linkage map of Raphanus was constructed with 180 individuals of F₂popilation from a hybrid of Nau-WH-04 (Raphanus sativus L.)×Lanhuazi (Raphanussativus L. var raphanistroid) by using morphological marker and molecular marker (RAPD,ISSR and RAMP markers). A totle of 172 marker loci were assayed in the population, andsix markers were not segregated in the F_z population. The map consists of 13 linkagegroups, which include 78 genetic markers and covers 1433.7 cM with an average geneticdistance of 18.4cM. 78 out of 166 genetic markers were located on the thirteen LGs,including 3 morphological markers, 55 RAPD markers, 6 ISSR markers and 14 RAMPmarkers, and among them, 46 marker loci derived from parent Lanhuazi, 31 marker locifrom another parent Nau-WH-04. the remaining Ninety (54.2ï¼…) genetic markers wereunmapped. There were several big gaps and some little linkage groups in the map due tothat RAPD markers are dominant and random distributed on the chromosome, and thecross-over value between different section of chromosome are heterogenous, this causedthe genetic distance and the map length were great.