Argostemma pictum (Rubiaceae), a species occurring in Myanmar, Thailand, Laos and Peninsular Malaysia, is newly reported for the flora of Vietnam; a description, photographs, information on ecology and taxonomic notes are also presented. In order to facilitate identification, we provide an identification key and checklist to the 10 known Argostemma species in Vietnam.

Essential oils from the leaves of Fokienia hodginsii (Dunn) A. Henry & H. H. Thomas and Amentotaxus argotaenia (Hance) Pilg. from Vietnam were obtained by hydrodisitllation and the chemical components determined by gas chromatography (GC) and gas chromatography coupled with mass spectrometry (GC/MS). Also the microdilution broth assay was used to test the antimicrobial activity of the essential oil. The yield of the essential oil was 0.22% (v/w). The major components of F. hodginsii were α-pinene (73.2%), limonene (10.3%), myrcene (4.1%) and β-pinene (2.6%). Amentotaxus argotaenia feature essential oil with α-pinene (20.4%), δ-cadinene (7.8%) and β-selinene (7.6%) as main compounds. The leaf essential oil of F. hodginsii displayed potent antimicrobial activity towards the Gram-positive microorganisms of Enterococcus faecalis ATCC 29212 and Bacillus cereus ATCC 14579 with minimum inhibitory concentration (MIC) values of 32.0 μg/mL and 64.0 μg/mL, respectively. The essential oil of A. argotaenia showed activity against E. faecalis ATCC 29212, Staphylococcus aureus ATCC 25923 and Bacillus cereus ATCC 14579 with MIC value of 64.0 μg/mL; as well as Pseudomonas aeruginosa ATCC 27853 (MIC, 32.0 μg/mL). Additionally, the essential oil of A. argotaenia exhibited the most anti-candidal action towards Candida albicans ATCC 10231 with MIC value of 32.0 μg/mL. The chemical constituents and antimicrobial activity of the essential oils of F. hodginsii were being reported for the first time.

Amentotaxus argotaenia (Hance) Pilg. is a threatened conifer with a wide distribution range from North to Central Vietnam due to habitat loss and over-exploitation. To provide information for its conservation and sustainable management, in the present study, genetic diversity and population genetic structure for 200 trees from eight populations, representing the natural distribution range of this species were estimated using nuclear microsatellites. The results showed a moderate genetic diversity of A. argotaenia (H_O = 0.331, H_E = 0.358). Significant heterozygosity deficits were detected in three populations in the Northeast area. Genetic differentiation was low in the same distribution area and high in different areas. However, the gene flow among the studied populations was relatively high (N_m = 1.17). Habitat fragmentation, geographical distance and high mountain range can be the major factors that reduce gene exchange between different areas. Various clustering analyses distinguished three major genetic groups related to the three distribution areas of this species in Vietnam. Based on the study results, we propose that some populations could be prioritized for in situ conservation due to their high genetic diversity with high allelic richness or private alleles, meanwhile other populations should be collected for ex situ conservation as genetic resources in the future.