Incongruent phylogenies and its implications for the study of diversification, taxonomy and genome size evolution of <i>Rhododendron</i> (Ericaceae)

PREMISERhododendron L. (Ericaceae Juss.), is the most species-rich genus of woody flowering plants with &gt; 1000 species. Despite the interest in the genus and numerous previous phylogenetic analysis, the infrageneric classification for the genus is still debated, partly due to its huge diversity, partly due to homoplasy in key characters and partly due to incongruence between phylogenetic markers. Here, we provide a broad coverage of representative species of all Rhododendron subgenera, sections, and most subsections to resolve its infrageneric phylogeny or highlight areas of incongruence, support previous analyses of diversification patterns and establish a relationship between genome size evolution and its diversification.METHODSWe generated sequences of two plastid (trnK and trnL-F) and two nuclear (ITS and rpb2-i) markers for a total of 259 Rhododendron species, and used likelihood and Bayesian statistics to analyze the data. We analyzed the markers separately to discuss and understand incongruence among the data sets and among previous studies.RESULTSWe found that the larger a subgenus, the more strongly it is supported as monophyletic. However, the smaller subgenera pose several problems, e.g., R. subgen. Azaleastrum consists of two sections inferred to be polyphyletic. The main shift to higher diversification in the genus occurred in the Himalayan/SE Asian clade of R. subgen. Hymenanthes. We found that polyploidy occurs in almost all subgenera but most polyploid species are within R. subgen. Rhododendron sections Rhododendron and Schistanthe.CONCLUSIONWhereas previous reports stated that genome sizes of tropical plants are lower than those of colder and temperate regions in angiosperms in general, our study provides evidence for such a shift to small genome-tropical species within a genus. Taken together, we see the merit in the recognition of the five major clades at the sub generic level but given the amount of incongruence a large amount of species cannot be confidently assigned to one of these five clades. Further, genome-wide data will be necessary to assess whether these currently unassignable taxa are independent taxa, assignable to one of the five major clades or whether they are inter-subgeneric hybrids.</jats:sec

La Croix du Nord : supplément régional à la Croix de Paris ["puis" grand journal quotidien du Nord de la France]

14 mai 19121912/05/14 (A23,N7864).Appartient à l’ensemble documentaire : NordPdeC

Additional file 3: Figure S3. of Assessment of cytotoxicity exerted by leaf extracts from plants of the genus Rhododendron towards epidermal keratinocytes and intestine epithelial cells

Overview of mitochondrial morphology in IEC6 and HaCaT cells after a 24h-exposure to three different concentrations (5, 50 and 500 μg/mL) of Rhododendron leaf extracts. Confocal fluorescence images of IEC6 (a, left) and HaCaT (b, right) cells labeled with MitoTracker® Red CMXRos. Cells treated with 0.5 % DMSO served as controls, A) R. hippophaeoides var. hippophaeoides, B) R. minus, C) R. rubiginosum, D) R. cinnabarinum, E) R. ferrugineum, F) R. polycladum, G) R. concinnum, H) R. xanthostephanum, I) R. anthopogon ssp. anthopogon, J) R. ambiguum, K) R. hirsutum, and L) R. racemosum. Bars represent 50 μm. (TIFF 11640 kb

Comparison of the polyphenolic profile and antibacterial activity of the leaves, fruits and flowers of Rhododendron ambiguum and Rhododendron cinnabarinum

Abstract Background Rhododendron species have been traditionally used in countries like China, Nepal, Russia and North America for treating human diseases. These species are known to be a good source of polyphenolic plant secondary plant metabolites. They are known to have beneficial health properties for humans and have been used to treat diseases like asthma, skin diseases. In this contribution we investigate the phenolic profile and antibacterial activity of extracts from several plant organs including for the first time from leaves of different development stages. Methods In this study, the polyphenolic profile of fruits, flowers and leaves of different ages of Rhododendron ambiguum and Rhododendron cinnabarinum were studied by using HPLC–MS and compounds identified based on high resolution masses and identity of tandem mass spectra, UV/VIS spectra and retention times if compared to standards. Results Fifty-nine different polyphenols including isomers were identified in these species by their fragmentation pattern and high resolution data. Also, the antibacterial activity of these parts (leaves, fruits and flowers) against gram-positive bacteria was studied. Conclusion The leaves and fruits contained more polyphenols than the flowers. With the exception of flowers, the fruits and leaves of both species were also determined to have a significant antibacterial effect against four gram-positive bacteria