Polymorphism Analysis And Screening Of SSR Molecular Markers In Turnip

In recent years,the research methods that constructing a genetic map with the molecular markers and then study the traits of the species developmented very fast,especially the investigation of the soybean,rice and cabbage.But,the records of turnip whith molecular markers are still scarce,especially for the data of the light signal transduction is even more uncommon.It is very important to build a high density genetic map in order to study the light signal transduction.The base of a genentic map is a sufficient number of molecular markers.Because the available turnip SSR markers is limited,it is necessary to develop more SSR markers.In this thesis,we developed SSR markers by ’Tsuda’ plants and ’Yurugi Akamaru’ plants,including gssr and est-ssr, then choiced better in polymorphisms and stable primers through polymorphism screening and analysised their polymorphism characteristics.Clonig the differences SSR loci between the two species than contrast the difference between the two sequence.Analyze the SSR primers results from different sourcesWe obtained the following main results:1The gSSR primers screening and polymorphism analysisSearch SSRs by the Brassica rapa genome sequence published in GenBank.Then combined with Primer3.0.We developed680new SSR primers. We analysised the amplification of the new680pairs of SSR primers by ’Tsuda’ plants and ’Yurugi Akamaru’ plants. There were565pairs of effectively amplified SSR primers and141of them were polymorphic among two species. No correlation was observed between SSR repeat length with polymorphism levels.But the data shew that tri-nucleotide were better polymorphism. At the same time,the SSR repeat seven times were better then the other kinds of repeats.2The EST-SSR primers’ screening and polymorphism analysisSearching3803ESTs of turnip from Northeast Forestry University by the SSRHunter proguam.There are143SSRs distributed in143ESTs,accounting for3.76%of the total number of EST,the average distance of9.50kb a SSR, included27repeat elements.Among them,din-nucleotide an tri-are most,which accounted for nearly97.20%of tltal SSRs,the other types’proportion are less than3%.Based on the143ESTs,we designed and synthesized90pairs of EST-SSR primers,and analysised the amplification of the these primers by ’Tsuda’ plants and ’Yurugi Akamaru’ plants. There were85(94.44%)pairs of effectively amplified EST-SSR primers and13(15.3%) of them were polymorphic among two species.This result show that development of EST-SSR primers in the turnip is better usability.We cloned the BrlEST15primer SSR loci that differet between the tow speices,the result show that there are one different repeat motif.3The SSR polymorphism analysis from different sourcesIn this study,we developed931pairs of SSR primers,including90pairs of EST-SSR.According to the source,these SSR primers can be divided into five kinds,gSSR from B. Rapa(including10pairs of primers from Japan national vegetable and Tea Science Research Institute),B.Oleracea,Brassica napus,B.nigra,and EST-SSR are all from Tunip ’Tusda’ cDNA.Through analysis of polymorphism,we get the data is that the polymorphism of SSR primers from B. Rapa is the highest(12.12%) and only1.77%of SSR primers from B.nigra is polymorphism.The results show that the SSRs from B. Rapa which is the closedest with turnip are best.