Study On Taxonomy And Phylogeny Of Persicaria In China

Persicaria(L.)Mill.is a genus of herbaceous flowering plants in the tribe Persicarieae in the subfamily Polygonoideae in the Polygonaceae family.There are about 150 species in this genus,most of which are distributed in temperate regions.Some species of Persicaria have important ecological function and economic value.The taxonomic boundary of Persicaria has always been controversial.Generally,the following two opinions are held: on the one hand,it should be regarded as a section of Polygonum sensu lato,i.e.section Persicaria;on the other hand,it recognizes its status at the genus level.Based on the morphological and molecular data,Persicaria was isolated from Polygonum sensu lato and established as Persicaria.At present,most scholars support that Persicaria can be divided into four groups,namely section Cephaiophilon,section Persicaria,section Echinocaulon and section Tovara.However,there are still many controversies about the relationships among the four sections in Persicaria,the relationships among the three species of section Cephaiophilon(Persicaria runcinata,Persicaria capitata,and Persicaria nepalensis)and the systematic position of Persicaria bungeana,which need more evidences.In addition,most of the previous studies on Persicaria are included in the related work of other groups.In these studies,there are few species involved in Persicaria and the molecular markers used are also limited,so it is not possible to conduct a comprehensive and systematic study on the species of Persicaria.The purpose of this study is to study the morphology and molecular systematics of Persicaria in China,mainly to solve phylogenetic relationships of four sections,interspecific relationships of section Cephalophilon,and the systematic position of Persicaria bungeana.The main contents and results of this study are as follows:1.In this study,micromorphological characteristics of leaf abaxial epidermis of 32 Persicaria species were observed.The results showed that the shape of leaf abaxial epidermis cells,the pattern of anticlinal wall,the type of stomatal apparatus,the ratio of length to width of stomatal apparatus,and stomatal index of Persicaria had some taxonomic significance,and could provide some taxonomic evidence for the classification of some species.Through the analysis of stomatal apparatus types,it was found that stomatal apparatus could be used as an important character for the subgenus grouping,and provided a certain morphological basis for solving the genetic relationship between species of section Cephaiophilon.In addition,the epidermal cells of P.bungeana were polygonal in shape,the anticlinal walls were straight arched,and the stomatal apparatus were atypical.The characters of lower epidermis of these leaves were similar to those of section Persicaria.Therefore,this study supported that Persicaria bungeana should be classified into section Persicaria.2.In this study,macromorphology and micromorphology of achene of 35 Persicaria species were observed.The results showed that macroscopic morphological characteristics(shape,color,etc.)of achenes were very similar,which could not be used as an important character for grouping,but the surface ornamentation of pericarp provided a new basis for the systematic division of Persicaria.The pericarp surface ornamentation of three sections(section Cephaiophilon,section Echinocaulon and section Tovara)were similar to that of section Persicaria.The surface ornamentation of the pericarp of section Tovara is most similar to that of Persicaria taquetii and Persicaria viscosa in the section Persicaria.Micromorphological features of the achene surfaces provided important morphological evidence for the definition of sections level and species level of Persicaria.3.The complete chloroplast genome sequences of 29 Persicaria plants were obtained by high-throughput sequencing technology.Combined with the downloaded one chloroplast genome sequence of Persicaria,comparative genomics analysis was carried out.The results showed that the chloroplast genome of Persicaria plants was relatively conservative,ranging from 157,889 bp to 160,982 bp,which was composed of LSC,SSC and IRa/b.The difference was mainly in the LSC region.The content of GC of these chloroplast genomes was about 38.06%.Compared with other regions,the content of GC in reverse repeat region was the highest.The chloroplast genome contained 113 unigenes,included 79 coding genes,30 t RNA genes and 4r RNA genes.In particular,A/T-ending codons were preferred.The chloroplast genome of Persicaria was rich in repeats and SSRs,which provided more valuable genetic resources for species identification and phylogeny of Persicaria.4.The results showed that the chloroplast genome of Persicaria was highly conserved,but still showed a certain degree of sequence differentiation.The conservation of IR region was higher than that of LSC region and SSC region.By comparing the percentages of parsimony informative loci,17 high mutation regions were screened out in this study.Understanding and utilizing these mutation hotspots can better serve the phylogenetic study of Persicaria.5.Based on the seven sets of data matrices,the ML trees constructed for 30 Persicaria species have no significant conflict topology,which supported that Persicaria is a monophyletic group.Persicaria was divided into four branches,namely section Cephalophilon,section Tovara,section Echinocaulon,and section Persicaria.Among them,the phylogenetic tree based on chloroplast genome was the best in solving the phylogeny of Persicaria,and the support rate of main branch nodes was high.Combined with the study of leaf epidermis and achene micromorphology,the phylogenetic relationship of the four sections has been well solved.Section Cephalophilon was the base group of Persicaria.Section Tovara and section Persicaria were closely related.The branches formed by section Tovara and section Persicaria form sister group with section Echinocaulon.In addition,the interspecific relationship of section Cephalophilon and the systematic position of P.bungeana were well solved.Compared with previous studies,using chloroplast genome can effectively improve the resolution of phylogenetic relationships in this genus.