The Development Of SSR Markers And The Construction Of Genetic Linkage Map In Brassica Napus

In this study,a genetic linkage map of Brassica napus was constructed with the previously published and newly developed SSR markers using 93 DH lines derived from the No.2127-17 and Zhongyou821.Comparisons this map with the genome of Arabidopsis thaliana and standard map of Brassica rapa were performed.The main results are as follows:1.Three hundred seventy nine(43.2%) of 877 published SSR markers showed polymorphism between two parents 'No.2127-17' and 'ZhongYou821'2.A total of 3436 SSR markers were developed from public database.They were named as "BnGMS","BrGMS","BoGMS","BnEMS","BrEMS","BoEMS" according to their sources.The SSR sequences of these primers had repeat motifs from mononucleotide to pentanucleotide.The most abundant repeat motifs were dinucleotide and trinucleotide repeats.Among the dinucleotide repeat motifs,more AG dinucleotide repeats,followed in abundance by AT and AC repeats.GC repeats are extremely rare.Among the trinucleotide repeat motifs,a higher frequency of AAG repeats was identified.881(25.6%) pairs of primers which polymorphism in two parents were identified.The EST-SSRs("BnEMS","BrEMS" and "BoEMS") were more polymorphism than others.3.Genotypes of the DH lines were surveyed with the 1260 polymorphic SSR markers. A high-density genetic linkage map was constructed using JionMap3.0.The linkage map consisted of 19 linkage groups,which include 845 SSR markers and have a total length of 1898.5cM with an average interval of 3.4cM between adjacent loci. As for the different linkage groups,the lengths varied from 27.4cM to 211.0cM. The average marker intervals varied from 2.6cM to 8.0cM.4.The sequences of the 845 SSRs located on the linkage map were compared with the genome of Arabidopsis thaliana.Of which,534 sequences had homologous with Arabidopsis.The five chromosomes of Arabidopsis were represented by homologous sequences distributed throughout the nineteen B.napus linkage groups. These homologous regions covered 821 cM.Some regions were even homologous with two or three Arabidopsis chromosomes.The data provided strong evidence to support the hypothesis that B.napus and the model plant-Arabidopsis had a common ancestor.5.Comparison between the linkage map of Brassica napus and the standard map of Brassica rapa showed that NI-N10 of Brassica napus and R1-R10 of Brassica rapa had synteny.Furthermore,N12 and R2,N16 and R7,N19 and R9 had some homologous regions,respectively.