Molecular Analysis And Fruit Anatomy In Polygonum L. And Related Genera

The phylogenetic relationships of Polygonum L. and related genera were comprehensively investigated using integrated studies on fruit anatomy and molecular phylogeny, along with field and herbarium investigations. The results are summarized as follows:1. Anatomy of fruitSections of fruits, coupled with surface patterns were studied under LM in Polygonum L. and related genera. Based on the straight or undulating excocarp and the different lumen, two types of the excocarp cell can be recognized in the species studied. In typeâ… , the excocarp is usually thickened and correlated with the straight or undulating outline of the anticlinal walls, and sections Persicaria, Tovara, Echinocaulon, and Cephalophilon of the genus that studied this investigation, its anatomy can be used consistently to delimit genera more than any other character of the fruit. In typeâ…¡, Polygonum sect. Aconogonon and Polygonum sect. Bistorta which we investigated in this study can be delimited by the square to rectangular cells with a narrow dichotomously branching lumen and straight anticlinal walls; both genera share the same pattern of the structre of cell, have close relationship. Different structure of excocarp in species of Atraphaxis, Fallopia and sect. Polygonum can be found. Fagopyrum have two types of exocarps types: the thin exocarps and thick exocarp with dichotomously branching lumen corresponding to the two groups of Fagopyrum.2. Molecular phylogenyPhylogenetic analyses 36 species of Polygnoum s.l. and related genera based on sequence of the nrITS using maximum parsimony. The results of phylogenetic analyses suggest Polygonum s.l. related genera is not a monophyletic group, and correspond to division of Polygoneae and Persicarieae. Fagopyrum are nested within Persicarieae. It is noteworthy that Koenigia and Aconogonon compose a monophyletic group with a close relationship to Bistorta.3. Reappraisal of the generic status of PteroxygonumGross morphology, fruit anatomy, tepal venation, pollen morphology, chromosome number and ITS sequence of Pteroxygonum Damm. et Diels as well as other related genera (Polygonum., Fallopia, Reynoutria, Fagopyrum and Antenoron) have been investigated, to evaluate the generic status of Pteroxygonum. Pt. giraldii has three sharp horns at the base of fruit, which is distinctive among all the genera investigated. Upon observation of fruits under a light microscope (LM), the exocarp of Pt. giraldii is usually thickened and delimited by the rectangular cells with some sporadic undulating lumen, while that of Fagopyrum is thin-walled and isodiametric to rectangular in the cell shape. Analysis of tepal venation was performed under a stereomicroscope, and two types of tepal venation were found in Fagopyrum and Pteroxygonum. The typeâ… is trifid, observed in Pt. giraldii, F. esculentum Moench, F. dibotrys (D.Don) Hara and F. tataricum (L.) Gaertn. The typeâ…¡, found in F. caudatum (Sam.) Harald, F. urophyllum (Bur. et Franch) H. Gross and F. gracilipes (Hemsl.) Hedb, has the main vein extending from tepal base with some secondary veins. Evidence from tepal venation supports the previous classification in which Fagopyrum can be divided into a large-achene group and a small-achene group. Pollen morphology was investigated under a scanning electron microscope (SEM). The exine ornamentation of Pt. giraldii was finely reticulate with lumina diameter wider than muri width. The exine ornamentation in all the examined Fagopyrum species is, however, prominently sunken punctuate. The phylogenetic analysis of nuclear ribosomal DNA (nrDNA) ITS sequences in Pteroxygonum and related genera indicated that all the species form a well-supported monophyletic group with two clades. One includes Polygonum sect. Avicularia Meisn., genus Fallopia and genus Reynoutria, and the other consists of other sections of Polygonum, genus Fagopyrum and Pteroxygonum. The latter clade can be divided into two subclades. Fagopyrum species compose the first one, while Pterxoygonum giraldii, Polygonum (except sect. Avicularia) and Antenoron form the second one. In consideration of the above evidence, we conclude that Pteroxygonum is an independent genus, in Tribe Persicarieae, and should not be merged into genus Fagopyrum.