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Dendrobium catenatum (Dendrobium officinale) is a valuable genuine herb. The source of this species is difficult to be identified by traditional methods including morphology, spectroscopy, and chromatography. We used the restriction site-associated DNA sequencing (RAD-seq) approach to perform the high-throughput sequencing of 24 D. catenatum provenances. In this study, 371.18 Gb clean data were obtained, and 655,057 high-quality SNPs were selected after their filtration. We used phylogenetic tree, genetic structure, and principal component analyses to examine the genetic diversities and genetic relationships of the 109 accessions. We found that D. catenatum could be divided into two groups, and each group was closely related to the distribution of the sampling sites. At the population level, the average nucleotide diversity (π) of the D. catenatum population mutation parameters was 0.1584 and the expected heterozygosity (HE) was 0.1575. The GXLPTP07 accessions showed the highest genetic diversity in terms of the private allele number, observed heterozygosity, and nucleotide diversity. The Mantel test showed a significant positive correlation between the genetic and geographic distances among the overall distribution. A genetic information database of D. catenatum was established, which confirmed that RAD-seq technology has the potential to be applied in the identification of medicinal Dendrobium of different origins.

A new species of Gastrodia (Orchidaceae: Epidendroideae, Gastrodieae), G. qingyunshanensis, is described and illustrated from Guangdong, China. It is closely related to G. appendiculata C. S. Leou & N. J. Chung but can be distinguished by an urceolate (vs bell-like) and dark brown (vs pale greenish brown) perianth tube, the smaller petals (2.5 × 1.6 mm vs 4–5 × 5–6 mm), the shape of lip (oblong, 3×1.6mm vs ovate, 6–7×5mm), lack of elevated calli at the base of petal (vs having calli), and an appendage shorter than column (vs equal to column). The new species is only reported to occur on Qingyunshan Nature Reserve, Wengyuan County, China, and it is proposed to be Vulnerable (VU) according to the IUCN criteria.

The subtribe Aeridinae, which contains approximately 90 genera, is one of the most diverse and taxonomically puzzling groups in Orchidaceae. In the present study, the phylogenetic relationships of Aeridinae were reconstructed utilizing five DNA sequences (ITS, atpI-H, matK, psbA-trnH, and trnL-F) from 211 taxa in 74 genera. The results of the phylogenetic analyses indicate that Aeridinae is monophyletic and that the subtribe can primarily be grouped into 10 clades: (1) Saccolabium clade, (2) Chiloschista clade, (3) Phalaenopsis clade, (4) Thrixspermum clade, (5) Vanda clade, (6) Aerides clade, (7) Trichoglottis clade, (8) Abdominea clade, (9) Gastrochilus clade, and (10) Cleisostoma clade. In our examination, most genera of Aeridinae were well-supported as monophyletic, and several genera, namely, Pteroceras, Cleisostoma, Vandopsis, Diploprora, Malleola, and Robiquetia, were found to be polyphyletic as currently circumscribed. In addition, several classifications of intra-genera, such as the subgenus Codonosepalum of Taeniophyllum and the section Gastrochilus of Gastrochilus, were also revealed to be paraphyletic. Due to the many questions raised by our phylogenies, the present study may serve as a reference for future taxonomic studies of Aeridinae.

Sequence of 15 SRAP selected primer combinations. (DOCX 14Â kb)

Results of pairwise population Fst analysis. (DOCX 14Â kb)

Background Loropetalum subcordatum is an endangered species endemic to China that is characterized by narrow distribution, small population size, and delayed fertilization. However, the genetic diversity of the entire extant natural and ex situ populations has not been assessed to date. In this study, we evaluated the genetic diversity and structure of six natural populations and a single ex situ population (the only known ex situ population of L. subcordatum) using sequence-related amplified polymorphism data. Results In total, 553 reliable DNA bands, of which 359 (63.28%) were polymorphic, were amplified by polymerase chain reaction with combinations of 15 primers. Low average gene diversity within populations and high genetic differentiation were detected in L. subcordatum. A Mantel test demonstrated that there was a positive correlation between genetic and geographic distances, indicating that significant genetic divergence was likely the result of geographic isolation among natural populations. Furthermore, based on genetic structure patterns, populations of L. subcordatum were divided into three clusters. Group 1 was composed of specimens from Libo, Guizhou Province (GZ) and Huanjiang, Guangxi Zhuang Autonomous Region (GX). Group 2 was composed of Mt. Wuguishan, Guangdong Province (GD). Group 3 was composed of three populations in Hong Kong Special Administrative Region. Additionally, clonal reproduction probably existed in GD population. According to the genetic information analysis and field survey, the ex situ population did not match its source population (GD) in terms of genetics, and its habitat was different from the original natural habitat. We observed that a few individual GD seeds were needed to improve ZS ex situ in the future. Conclusions Compared to previous SRAP-based studies of endangered plants, L. subcordatum had extremely low average gene diversity within populations and high genetic differentiation among populations. At present, the unique ex situ population has not been successful due to non-representative samples being taken, a smaller population size, and man-made changes in habitat. Potential strategies are suggested to improve the conservation of this species. Electronic supplementary material The online version of this article (10.1186/s12863-018-0599-6) contains supplementary material, which is available to authorized users.

This publication is a precursor for the account of Trigonostemon (Euphorbiaceae) for the Flora of China, based on specimens at several herbaria in the U.S.A. (Harvard University, Missouri Botanical Garden, and the Smithsonian Institution) and major herbaria in China. The genus Trigonostemon (Euphorbiaceae: Crotonoideae, Trigonostemoneae) in China is revised. Twelve species and varieties are placed in synonymy, that is, Trigonostemon petelotii, T. kwangsiensis vars. kwangsiensis and viridulis, and T. lii are combined with T. bonianus; T. harmandii, T. leucanthus var. hainanensis, and T. wui are combined with T. chinensis; T. gagnepainianus and Prosartema gaudichaudii are combined with T. howii; T. heterophyllus is combined with T. flavidus; and T. lutescens is combined with T. fragilis. Trigonostemon fragilis is reported as new to Myanmar. A key to the species of Trigonostemon in China is given.

A new species of Vanda , V. malipoensis , from Yunnan, China, is described and illustrated in this study based on morphological and molecular evidence. Detailed morphological comparisons between the newly discovered orchid and other members of Vanda s.l. indicate that V. malipoensis is similar to V. christensoniana and V. nana . The new plant differs from the former species by the presence of inflorescences with sparse and smaller flowers, a shorter column and caudiculate pollinia, and it differs from the latter by the presence of longer inflorescences with fully open flowers and erect sidelobes of the lip. Molecular phylogenetic analyses based on nrITS and plastid datasets ( atpI-atpH , matK , trnH-psbA , and trnL-F ) also support the conclusion that V. malipoensis is a new species in section Ascocentropsis of Vanda s.l. and is sister to V. nana and this pair to V. christensoniana . Given the observed discrepancy between the plastid and nrITS results, hybridization may have been involved in the evolution of this set of species.

Bulbophyllum lipingtaoi , a new orchid species from Yunnan, China, is described and illustrated. Detailed comparative morphological analyses indicate that this new orchid is distinct from other species of Bulbophyllum in having a single-flowered inflorescence with a scape arising from the node of the rhizome, entire margins of sepals and petals, and lateral sepals twisted near base. Furthermore, molecular phylogenetic analyses based on nuclear ribosomal ITS and plastid DNA ( mat K and atp I- atp H) support the placement of B. lipingtaoi as a member of section Brachyantha . Section Brachyantha is usually characterized by a 2- to many-flowered inflorescence, hence the solitary flower of B. lipingtaoi should be treated as an apomorphy.