Analysis Of Genetic Diversity In Coptis And Morphologic Investigation Of Protocorm-like Bodies In Dendrobium Candidum

To investigate the genetic relationship, diversity and the factors for the divergence in genomes through RAPD, eleven samples in genus Coptis were introduced into the study. In particular, four populations within Coptis omeinesis species were studied on polymorphic sites to analyze the trend in gene flow and genetic distances. The results are showing as following:1. Through amplifying genomes of eleven samples in Coptis,771sites were detected by82random primers. Each primer amplified9.5sites. Among these sites,688sites were polymorphic, which occupied89.37%of the amount. Based on this result, we concluded that the polymorphisms between these species in genus Coptis are in abundance. For the four populations within Coptis omeinesis,510sites were amplified, among which198were polymorphic. The average polymorphic rate reached38.8%, which was much lower comparing with it between species.2. Phylogenetic tree was constructed based on RAPD data set, and the clustering result was consistent with traditional morphological classification. Eleven samples were categorized into four groups when similarity coefficient was greater than0.72:Coptis chinensis Franch, Coptis deltoidea, Coptis omeinesis and Coptis linearisepala. Coptis chinensis Franch, in a single branch, was least similar with other three species. Two populations of Coptis deltoidea were clustered into a branch, and the similarity was very significant between the populations. When similarity coefficient was above0.84, Coptis omeinesis and Coptis linearisepala were diverged into two branches. Huangwan population and double-wings type of Sandaohe population were clustered into a group while Baiya population, Renpengzigou population and phoenix-tail type of Sandaohe population were grouped together.3. Gene flow within Coptis omeinesis species was analyzed by applying POPGENE. The statistic showed that polymorphic rate on population level was26%, with Shannon’s Information index0.1852, genetic differentiation index (Gst)0.3608and estimate of gene flow (Nm)0.2912. The result indicated that majority of the variations occurred in genomes existed within population instead of gene flow across the populations. The low gene flow was probably a main factor for genetic diversity between populations, but the affect of genetic drift cannot be expelled. The effect of natural habitat was still dominant in deciding the genetic structure of genomes. For sample5(Sandaohe population, phoenix-tail type), the only exception during the classification, we concluded that there were still tiny genetic discrepancy among the samples with different phenotypes, although the individual differences would not influence the evolution of the whole population.Through applying plant paraffin section technique, morphology of D. candidum embryos during development of PLBs was investigated. Uneven hairy protuberances were observed after15d incubation from callus. With the development of the explants, some of the protuberances grew into buds, and the surfaces of tissues around buds were caved inside to generate cup-like shape. By observation of paraffin sections, the existence of globular was proved and PLBs were found to be derived from somatic embryo structure within the embryonic cells.