Studies On Phylogenetic Relationships Between Several Taxa Of Dendranthema And Ajania

Several representative taxa of Dendranthema and Ajania from China and Japan were used in this study. Morphological cluster analysis, PCR-RFLP analysis and DNA sequence analysis were conducted. The phylogenetic relationship between the taxa of Dendranthema and its close related Ajania genus were reconstructed based on above data. The origin of cultivated chrysanthemum was also discussed.The results were as follows:1. There were obviously morphological differences between D. arcticum and other Dendranthema species. DNA sequences analyses showed that D. arcticum and D. arcticum subsp. maekawanum were quite close to each other, but far away from other Dendranthema species. Obvious morphological differences were also observed between D. mongolicum,D. yoshinaganthum and other Dendranthema species. The results suggested that the genus Dendranthema should be classified into three Sections, i.e., Arctantherum, Dendranthema and Chlorochlamys, respectively. The Section Arctantherum should just comprise D. arcticum, D. arcticum subsp. arcticum and D. arcticum subsp. maekawanum. The Section Chlorochlamys should include D. argyrophyllum, D. mongolicum and D. yoshinaganthum. The Section Dendranthema is the main section consisted of the remaining taxa in Dendranthema.2. The parsimony-informative character rate of ITS and rpl16 in Dendranthema and Ajania species was 8.5% and 3.3%, respectively. Nuclear ITS sequence was more phylogenetic informative than chloroplast rpl16 sequence for the study on phylogenetic relationships between taxa of Dendranthema and Ajania. rpl16 had obvious length polymorphisms, the length of rpl16 sequence in Dendranthema and Ajania species had four types: 1069bp, 1077bp, 1080bp and 1084bp. The phylogenetic tree based on the combined dataset of ITS and rpl16 sequence could give more resolution and more branches than that based on sole ITS or rpl16 sequence data.In Dendranthema, D. indicum and D. nankingense is genetically close to each other, so is D. dichrum and D. lavandulifolium, D. japonicum and D. yoshinaganthum, D. dichrum and D. oreastrum, D. crassum and D. rhombifolium. Meanwhile, close relationships were observed between D. japonense and D. vestitum, D. lavandulifoium and D. boreale, D. zawadskii and D. weyrichii, respectively. However, it is more reasonable to treat them each as a unique taxon rather than treating each two taxa as a single taxon.In neighbor-joining analysis of DNA sequences, D. japonicum and D. japonicum var. wakasaense, D. arcticum and D. arcticum subsp. maekawanum, D. japonense and D. japonense var. debilis, D. vestitum and D. vestitum var. lanceifolium grouped next to each other, respectively. It suggested that they had very close relationship. Although D. zawadskii and D. zawadskii var. latilobum were not in the same group, the little pairwise distance between them also showed they had close relationship. However, in the cluster analysis based on the morphological characters, these species and their varspecies or subspecies had not get together, which suggested that the evolution of phenotype was incongruent with the evolution of genotype, the morphological characters had greater differentiation than the DNA sequences did.3. The digested fragments of rbcL-EcoRⅡ,rbcL-MspⅠ,ndhF-HinfⅠ,petA-MboⅠin A. pacifica,A. shiwogiku and Dendranthema species had no length polymorphisms. In DNA sequences analyses, A. pacifica and D. arcticum, D. arcticum subsp. maekawanum were in the same group, A. shiwogiku var. kinokuniense get together with other Dendranthema species. Therefore, A. pacifica, A. shiwogiku and A. shiwogiku var. kinokuniense, the representative taxa of Ajania, showed close relationships with some taxa of Dendranthema.A. pacifica and A. shiwogiku var. kinokuniense was similar on morphological aspect, but differed from those of Dendranthema species. The digested patterns of petA-MboⅡin A. pacifica,A. shiwogiku were different with other Dendranthema species, which further indicated that there were genetically different with most Dendranthema species to some extend.4. The cluster results based on 24 morphological characters and 1 biological character showed that some Chinese Dendranthema wild species, D. indicum, D. lavandulifoium, D. nankingense, D. dichrum were in the same group, so did most of the Japanese wild species. It indicated that the distribution of taxa from China or Japan is geographic distinctively. Dendranthema vestitum showed a relatively closer relationship with Japanese Dendranthema wild species, and the Japanese Dendranthema wild species are more evolved than the Chinese Dendranthema wild species. 5. In PCR-RFLP analyses, three cultivated chrysanthemum varieties D.×grandiflorum'Yinxing', D.×grandiflorum'Jinlingwanxia' and D.×grandiflorum'Shenma' had the same digested patterns with Chinese wild Dendranthema species, which indicated they had very close relationships, In DNA sequences analyses, these three cultivated chrysanthemum varieties get together. These varieties showed a very close relationship with the presumed ancestral species of D. indicum, D. vestitum, D. nankingense etc., especially closest to D. chanetii, while a relatively farer relationship with D. ornatum, D. japonense. The Japanese wild species have also played a significant role in enriching the varieties of modern chrysanthemum.