Phylogenetic Analysis Of Dioscorea Based On PsbA-trnH Gene And 18S RDNA

Dioscoreca plants are classified in the genus Dioscorea,family Dioscoreaceae,and order Dioscoreales.More thean 650 species are known to exist,the systematics of which remain uncertain.Dioscorea plants are annual or perennial twisted herbal liana with the kind of both medicine and food crops.Yam is the common name for some plant species in the genus Dioscorea(family Dioscoreaceae)that form edible tubers.These are perennial herbaceous vines cultivated for the consumption of their starchy tubers in Africa,Asia,Latin America,the Caribbean and Oceania.Dioscorea plants are more cultivated Dioscorea and alata in the long process of evolution in the genus.People in different areas often exchange their variety with each other,which lead the phenomenon of the Dioscorea in the market synonyms and homonym to be serious.It is difficult to distinguish the species and varieties each other by the traditional morphological classification in the process of cultivation and introduction process.It is more serious of homonym and synonym phenomenon in the market and it is particularly important for Dioscorea germplasm resources conservation and exploitation.Phylogenetic relationship was studied of 63 different samples of Dioscorea by the psbA-trnH gene sequences and 51 different Dioscorea samples by 18S rRNA genes respectively.The results are as follows:1.The relationship between species and germplasm could be accurately identify with big difference Euclidean distance of each sample according to Q cluster analysis of the 61 kinds of Dioscorea plants.61 Dioscorea samples are generally divided into two categories when the threshold is 7.41.2.The sequence length of all varieties is between 331 bp?418bp,and the sequence phylogenetic relationship is between 100%-50%,and the genetic distance is between 0.518?0.00 by the analysis of psbA-trnH gene sequences of 63 Dioscorea plants.There are 264 nucleotide mutation sites,205 informative loci and 178 conserved loci among these loci.It was showed obvious interspecific differences of the nucleotide sequences which can be clearly distinguished interspecific relationships.3.the results showed that the length of the sequence was between 1765bp-1652bp and the sequence phylogenetic relationship was between 49%-100%by analyzing the 18S rRNA gene of 51 Dioscorea samples.The genetic distance is between 0.000?0.508.4.There are closest relationship among Hainan yam,Yang Xi yam,Guangdong,Ming Huai-3 yam with genetic distance was 0.And the genetic relationship is strong among Qujing,Luliang and the Guangdong yam with the genetic distance was 0.Compared with the close genetic relationship,these strains are likely to be associated with alata or relatives by clustering psbA-trnH gene and 18S rRNA gene cluster with morphological indexes analysis.5.Henan(2013)and.other Henan yam is not gathered in a class in the clustering.It is speculated that the Henan(2013)is a mixed pseudo species.6.Yunnan Lijiang Rehe wild yam is in alone branch and a far relationship with yam(D.opposita Thunb.)and yam(D.aata L.)based on the clustering results of 18S rRNA gene.It is presumably belonging to other species.