Research On The Phylogeny Of Cultivated Chrysanthemum And Wild Relatives Based On Intergenic Sequence Of Chloroplast DNA

In this study, the phylogeny of 53 accessions concerning chrysanthemum cultivars and wild relatives were investigated using several intergenic sequence of chloroplast DNA which had been widely applied in previous researches. Phylogenic trees were structured in an attempt to study this problem and the origin of cultivars. Both results in this study and previous researches were compared. The reliability of molecular phylogeny methods based on DNA sequences was also tested.The accessions in this thesis included 27 germplasms of 26 chrysanthemum cultivars, and 26 germplasms of 16 wild relatives. The main results are:1. matK-trnK sequence had the highest polymorphism, which meant it was the most appropriate one for constructing the phylogenic tree of chrysanthemum and wild relatives. The results indicated that, although polymorphisms of different chloroplast DNA sequences varied widely, the phylogenic trees according to each sequence were consistent with findings. So it could be concluded that short fragments could represent the whole genome in molecular phylogeny research.2. The stitched bidirectional sequencing results of all accessions’matK-trnK sequence displayed 96 polymorphic loci in 476 effective bps (22.4824%). The phylogenic tree revealed that, all accessions were classified into 2 major clusters, and each cluster was further divided into 2 sub clusters. Ajania species and a majority of the Chrysanthemum species from Japan occurred in the same cluster, and most of ornamental chrysanthemum cultivars appeared on a sub cluster of this cluster, and C. occidentali-japonese var. ashizuriense and C. shimofomai showed the closest genetic relationship with them, indicating these two species were most likely their maternal ancestor. However most of the medicinal chrysanthemum cultivars weren’t together with them, and one medicinal cultivar was even in another major cluster, revealing that medicinal cultivars had different maternal ancestor with ornamental ones. 3. Relationships between accessions of the same species suggested that, intraspecific diversity of chloroplast genome existed in a wide range of chrysanthemum cultivars and wild relatives, especially C. vestitum and C. indicum. For some Ajania and Chrysanthemum species, the genetic relationships of chloroplast genomes between them were very close, even closer than between Chrysanthemum species. So their phylogeny was worthy of investigating.4. Incomplete concerted evolution was found in ITS sequences of chrysanthemum cultivars and wild relatives by purifying and sequencing the PCR products of some accessions, so studying phylogeny of them and origin of cultivated chrysanthemum adopting ITS sequence of nuclear genome was quite complicated and the method needed to be validated. Thus the reliability of the previous results had yet to be verified.5. By comparing the results with previous studies, differences between the results of molecular phylogeny based on DNA sequence and of molecular markers based on PCR-based restriction enzyme were found, and the author standed by the former.