Dalbergia L.f. is a pantropical genus consisting of 269 species of trees, shrubs, and woody lianas. This genus is listed in CITES Appendices because of illegal logging and trafficking driven by the high economic value of its heartwood. Some species are also used medicinally. Species identification of Dalbergia timber and herbs is challenging but essential for CITES implementation. Molecular methods had been developed for some timber species, mostly from Madagascar and Southeast Asia, but medicinal species in south China were usually not included in those studies. Here, we sequenced and assembled the chloroplast genomes of five Dalbergia species native to Hong Kong, four of which are medicinal plants. Our aim is to find potential genetic markers for the identification of medicinal Dalbergia species based on divergence hotspots detected in chloroplast genomes after comparative and phylogenetic analysis. Dalbergia chloroplast genomes displayed the typical quadripartite structure, with the 50 kb inversion found in most Papilionoideae lineages. Their sizes and gene content are well conserved. Phylogenetic tree of Dalbergia chloroplast genomes showed an overall topology similar to that of ITS sequences. Four divergence hotspots (trnL(UAA)-trnT(UGU), ndhG-ndhI, ycf1a and ycf1b) were identified and candidate markers for identification of several Dalbergia species were suggested.

To improve agricultural performance and obtain potential economic benefits, an understanding of phylogenetic relationships of Hyacinthus cultivars is needed. This study aims to revisit the phylogenetic relationships of Hyacinthus cultivars using complete chloroplast genomes. Nine chloroplast genomes were de novo sequenced, assembled and annotated from seven cultivars of Hyacinthus orientalis and two Scilloideae species including Bellevalia paradoxa and Scilla siberica. The chloroplast genomes of Hyacinthus cultivars ranged from 154,458 bp to 154,641 bp, while those of Bellevalia paradoxa and Scilla siberica were 154,020 bp and 154,943 bp, respectively. Each chloroplast genome was annotated with 133 genes, including 87 protein-coding genes, 38 transfer RNA genes and 8 ribosomal RNA genes. Simple sequence repeats AAGC/CTTG and ACTAT/AGTAT were identified only in ‘Eros’, while AAATC/ATTTG were identified in all cultivars except ‘Eros’. Five haplotypes were identified based on 460 variable sites. Combined with six other previously published chloroplast genomes of Scilloideae, a sliding window analysis and a phylogenetic analysis were performed. Divergence hotspots ndhA and trnG-UGC were identified with a nucleotide diversity threshold at 0.04. The phylogenetic positions of Hyacinthus cultivars were different from the previous study using ISSR. Complete chloroplast genomes serve as new evidence in Hyacinthus cultivar phylogeny, contributing to cultivar identification, preservation and breeding.

Asparagusspecies are widely used for medicinal, horticultural, and culinary purposes. Complete chloroplast DNA (cpDNA) genomes of threeAsparagusspecimens collected in Hong Kong—A.aethiopicus,A.densiflorus‘Myers’, andA.cochinchinensis—werede novoassembled using Illumina sequencing. Their sizes ranged from 157,069 to 157,319 bp, with a total guanine–cytosine content of 37.5%. Structurally, a large single copy (84,598–85,350 bp) and a small single copy (18,677–18,685 bp) were separated by a pair of inverted repeats (26,518–26,573 bp). In total, 136 genes were annotated forA.aethiopicusandA.densiflorus‘Myers’; these included 90 mRNA, 38 tRNA, and 8 rRNA genes. Further, 132 genes, including 87 mRNA, 37 tRNA, and 8 rRNA genes, were annotated forA.cochinchinensis. For comparative and phylogenetic analysis, we included NCBI data for four congenerics,A.setaceus,A.racemosus,A.schoberioides, andA.officinalis. The gene content, order, and genome structure were relatively conserved among the genomes studied. There were similarities in simple sequence repeats in terms of repeat type, sequence complementarity, and cpDNA partition distribution.A.densiflorus‘Myers’ had distinctive long sequence repeats in terms of their quantity, type, and length-interval frequency. Divergence hotspots, with nucleotide diversity (Pi) ≥ 0.015, were identified in five genomic regions:accD-psaI,ccsA,trnS-trnG,ycf1, andndhC-trnV. Here, we summarise the historical changes in the generic subdivision ofAsparagus. Our phylogenetic analysis, which also elucidates the nomenclatural complexity ofA.aethiopicusandA.densiflorus‘Myers’, further supports their close phylogenetic relationship. The findings are consistent with prior generic subdivisions, except for the placement ofA.racemosus, which requires further study. Thesede novoassembled cpDNA genomes contribute valuable genomic resources and help to elucidateAsparagustaxonomy.

The Smilacaceae is a cosmopolitan family consisting of 200–370 described species. The family includes two widely accepted genera, namely Smilax and Heterosmilax. Among them, the taxonomical status of Heterosmilax has been continuously challenged. Seven Smilax and two Heterosmilax species can be found in Hong Kong, with most of them having medicinal importance. This study aims to revisit the infra-familial and inter-familial relationships of the Smilacaceae using complete chloroplast genomes. The chloroplast genomes of the nine Smilacaceae species from Hong Kong were assembled and annotated, which had sizes of 157,885 bp to 159,007 bp; each of them was identically annotated for 132 genes, including 86 protein-coding genes, 38 transfer RNA genes, and 8 ribosomal RNA genes. The generic status of Heterosmilax was not supported because it was nested within the Smilax clade in the phylogenetic trees, echoing previous molecular and morphological studies. We suggest delimitating the genus Heterosmilax as a section under the genus Smilax. The results of phylogenomic analysis support the monophyly of Smilacaceae and the exclusion of Ripogonum from the family. This study contributes to the systematics and taxonomy of monocotyledons, authentication of medicinal Smilacaceae, and conservation of plant diversity.

Iris speculatrix is a rare and endangered plant first discovered in and native to Hong Kong. The whole chloroplast genome of I. speculatrix is 152,368 bp in length. It contained a large single copy region (82,003 bp), a small single copy region (17,941 bp), and two inverted repeats (26,212 bp). Phylogenetic analysis of 17 species of Iridaceae was conducted. I. speculatrix was found to be sister to a group of 12 Iris species, including I. setosa, I. lacteal, and I. uniflora. The sequenced chloroplast whole genome would be useful to understand the phylogeny and to conservation of I. speculatrix.

Emilia sonchifolia is a herb with antioxidant, anti-inflammatory, antitumor, and wound healing properties. The complete chloroplast genome (cp genome) of the genus Emilia was sequenced for the first time. The cp genome of E. sonchifolia is 151,474 bp in length. It contained a large single-copy (LSC) region (84,004 bp), and small single-copy (SSC) region (17,980 bp), and two inverted repeats (IRs, 24,745 bp). Phylogenetic analysis of 24 species was conducted. E. sonchifolia was found to be closely related to Pericallis hybrida and Dendrosenecio spp. The sequenced cp genome would be useful to understand the phylogeny and genomic studies of the genus Emilia.