DNA Barcoding Studies On Brassicaceae

Brassicaceae (Cruciferae ulma Brassicaceae) is annual, biennial or perennialherbs, which includes approximately more than330genera and3500species Widelydistributed all over the world. Brassicaceae,which has molecular biology andsalt-tolerant plants research model plants, has highly economic value. There are about102genera and412species in China.DNA barcoding is based on the recognition and identification of DNA fragmentsof species also as molecular systematics of the most cutting-edge method. It is notaffected by individual morphological characteristics, development level, and manyother restrictions affecting. It can supplement the insufficiency of the description ofspecies, and to speed up the species identification.This paper is based on the screening of cruciferous nuclear genome highlyconservative single-copy encoding protein gene fragment. As far as possible eliminateinterference factors such as single genetic variant of insufficient information andorthologous and collateral homologous. Ultimately determines the AT2G36450,AT1G30950as candidate fragment of DNA barcoding in plants. Author use genesequences of arabidopsis thaliana as a standard, design primers with those sequences,choose from18different cruciferous species and varieties for PCR amplification,obtaine gene sequences by sequencing of the PCR product. By neighbor-joiningmethod, Maximum parsimony method, Maximum likelihood method and bayesianmethod, use AT2G36450,AT1G30950gene fragment nucleotide sequence and theirjoint matrix from different samples to construct phylogenetic trees and molecularsystematics analysis.Use the single-copy of the nuclear genome encoding gene molecular systematicsanalysis,the result suggests that Brassica and Orychophragmus, Cardamine, Nasturtium andRorippa, Sisymbrium, Arabis and Capsella belong to respectively is divided intoseries. The parsimony-informative sites carried by them can reach to19%-24%,it hasgood distinction between cultivars belong to the same species, or the same species, the supporting values of those nodes were100%. Under the condition of theparsimony-informative sites increase gradually and the relationships among low-leveltaxonomic hierarchies affected by parallel series is gradually reduced, phylogenetictree topology structure present the ladder step by step, and has a good degree ofdifferentiation.The results show that Single copy of the nuclear genome encoding genefragments by MP method,ML method and bayesian method is used to constructphylogenetic tree analysis of the molecular systematics, Can be used as DNAbarcoding to locate taxonomic hierarchies in plant and provides strong support for thestudy of plant evolution, system evolution and germplasm resources research.