Myristica yunnanensis is a member of Myristicaceae. The M. yunnanensis chloroplast genome is found to be 155,923 bp in length and has a base composition of A (30.04%), G (19.28%), C (19.91%), and T (30.77%). The genome contained two short inverted repeat (IRa and IRb) regions (48,004 bp) which were separated by a large single-copy (LSC) region (87,088 bp) and a small single-copy (SSC) region (20,731 bp). The genome encodes 120 unique genes, including 85 protein-coding genes, 27 transfer RNA (tRNA) genes, and 8 ribosomal RNA (rRNA) genes. Further, complete chloroplast sequence of M. yunnanensis was aligned together with Horsfieldia pandurifolia and other Magnoliales and basal angiosperms species which have reported the complete chloroplast sequence. This complete chloroplast genome will provide valuable information for the development of DNA markers for future species resource development and phylogenetic analysis of M. yunnanensis.

Horsfieldia pandurifolia is a member of Myristicaceae. The H. pandurifolia chloroplast genome is found to be 155,695 bp in length and has a base composition of A (30.01%), G (19.31%), C (19.90%), and T (30.78%). The genome contained two short inverted repeats (IRa and IRb) regions (48,062 bp) which were separated by a large single copy (LSC) region (92,561 bp) and a small single copy (SSC) region (15,072 bp). The genome encodes 121 unique genes, including 86 protein-coding genes, 27 transfer RNA (tRNA) genes, and 8 ribosomal RNA (rRNA) genes. Further, complete chloroplast sequence of H. pandurifolia was aligned together with five other species which have reported the complete chloroplast sequence. This complete chloroplast genome will provide valuable information for the development of DNA markers for future species resource development and phylogenetic analysis of H. pandurifolia.

Horsfieldia amygdalina is a member of Myristicaceae. The H. amygdalina chloroplast genome is found to be 155,683 bp in length and has a base composition of A (29.99%), G (19.32%), C (19.92%), and T (30.77%). The genome contained two short inverted repeat (IRa and IRb) regions (37,754 bp) which were separated by a large single copy (LSC) region (86,931 bp) and a small single copy (SSC) region (30,998 bp). The genome encodes 121 unique genes, including 86 protein-coding genes, 27 transfer RNA (tRNA) genes, and 8 ribosomal RNA (rRNA) genes. Further, complete chloroplast sequence of H. amygdalina was aligned together with Horsfieldia pandurifolia, Myristica yunnanensis and other Magnoliales and basal angiosperms species which have reported the complete chloroplast sequence. This complete chloroplast genome will provide valuable information for the development of DNA markers for future species resource development and phylogenetic analysis of H. amygdalina.

Background: Myristicaceae was widly distributed from tropical Asia to Oceania, Africa, and tropical America. There are 3 genera and 10 species of Myristicaceae present in China, mainly distributed in the south of Yunnan Province. Most research on this family focuses on fatty acids, medicine, and morphology. Based on the morphology, fatty acid chemotaxonomy, and a few of molecular data, the phylogenetic position of Horsfieldia pandurifolia Hu was controversial. Results: In this study, the chloroplast genomes of two Knema species, Knema globularia (Lam.) Warb. and Knema cinerea (Poir.) Warb., were characterized. Comparing the genome structure of these two species with those of other eight published species, including three Horsfieldia species, four Knema species, and one Myristica species, it was found that the chloroplast genomes of these species were relatively conserved, retaining the same gene order. Through sequence divergence analysis, there were 11 genes and 18 intergenic spacers were subject to positive selection, which can be used to analyze the population genetic structure of this family. Phylogenetic analysis showed that all Knema species were clustered in the same group and formed a sister clade with Myristica species support by both high maximum likelihood bootstrap values and Bayesian posterior probabilities; among Horsfieldia species, Horsfieldia amygdalina (Wall.) Warb., Horsfieldia kingii (Hook.f.) Warb., Horsfieldia hainanensis Merr. and Horsfieldia tetratepala C.Y.Wu. were grouped together, but H. pandurifolia formed a single group and formed a sister clade with genus Myristica and Knema. Through the phylogenetic analysis, we support de Wilde’ view that the H. pandurifolia should be separated from Horsfieldia and placed in the genus Endocomia, namely Endocomia macrocoma subsp. prainii (King) W.J.de Wilde. Conclusion: The findings of this study provide a novel genetic resources for future research in Myristicaceae and provide a molecular evidence for the taxonomic classification of Myristicaceae.

Knema conferta is a member of Myristicaceae. The K. conferta chloroplast genome is found to be 155,744 bp in length and has a base composition of A (30.02%), G (19.30%), C (19.90%), and T (30.78%). The genome contained two short inverted repeat (IRa and IRb) regions (48,052 bp) which were separated by a large single copy (LSC) region (86,926 bp) and a small single copy (SSC) region (20,770 bp). The genome encoded a total of 128 unigenes, including 89 protein-coding genes, 31 transfer RNA (tRNA) genes, and 8 ribosomal RNA (rRNA) genes. Further, complete chloroplast sequence of K. conferta was aligned together with 2 species of Knema and 5 basal angiosperms species which have reported the complete chloroplast sequence. This complete chloroplast genome will provide valuable information for the development of DNA markers for future species resource development and phylogenetic analysis of K. conferta.

Horsfieldia kingii is a member of Myristicaceae. The H. kingii chloroplast genome is found to be 155,655 bp in length and has a base composition of A (30.03%), G (19.52%), C (19.72%), and T (30.73%). The genome contained two short inverted repeat (IRa and IRb) regions (48,052 bp) which were separated by a large single copy (LSC) region (86,912 bp) and a small single copy (SSC) region (20,691 bp). The genome encodes 123 unique genes, including 85 protein-coding genes, 27 transfer RNA (tRNA) genes, and 8 ribosomal RNA (rRNA) genes. Further, complete chloroplast sequence of H. kingii was aligned together with other 2 species of Myristicaceae and other 5 basal angiosperms species which have reported the complete chloroplast sequence. This complete chloroplast genome will provide valuable information for the development of DNA markers for future species resource development and phylogenetic analysis of H. kingii.