Alpinia katsumadai (A. katsumadai), Alpinia oxyphylla (A. oxyphylla) and Alpinia pumila (A. pumila), which belong to the family Zingiberaceae, exhibit multiple medicinal properties. The chloroplast genome of a non-model plant provides valuable information for species identification and phylogenetic analysis. Here, we sequenced three complete chloroplast genomes of A. katsumadai, A. oxyphylla sampled from Guangdong and A. pumila, and analyzed the published chloroplast genomes of Alpinia zerumbet (A. zerumbet) and A. oxyphylla sampled from Hainan to retrieve useful chloroplast molecular resources for Alpinia. The five Alpinia chloroplast genomes possessed typical quadripartite structures comprising of a large single copy (LSC, 87,248–87,667 bp), a small single copy (SSC, 15,306–18,295 bp) and a pair of inverted repeats (IR, 26,917–29,707 bp). They had similar gene contents, gene orders and GC contents, but were slightly different in the numbers of small sequence repeats (SSRs) and long repeats. Interestingly, fifteen highly divergent regions (rpl36, ycf1, rps15, rpl22, infA, psbT-psbN, accD-psaI, petD-rpoA, psaC-ndhE, ccsA-ndhD, ndhF-rpl32, rps11-rpl36, infA-rps8, psbC-psbZ, and rpl32-ccsA), which could be suitable for species identification and phylogenetic studies, were detected in the Alpinia chloroplast genomes. Comparative analyses among the five chloroplast genomes indicated that 1891 mutational events, including 304 single nucleotide polymorphisms (SNPs) and 118 insertion/deletions (indels) between A. pumila and A. katsumadai, 367 SNPs and 122 indels between A. pumila and A. oxyphylla sampled from Guangdong, 331 SNPs and 115 indels between A. pumila and A. zerumbet, 371 SNPs and 120 indels between A. pumila and A. oxyphylla sampled from Hainan, and 20 SNPs and 23 indels between the two accessions of A. oxyphylla, were accurately located. Additionally, phylogenetic relationships based on SNP matrix among 28 whole chloroplast genomes showed that Alpinia was a sister branch to Amomum in the family Zingiberaceae, and that the five Alpinia accessions were divided into three groups, one including A. pumila, another including A. zerumbet and A. katsumadai, and the other including two accessions of A. oxyphylla. In conclusion, the complete chloroplast genomes of the three medicinal Alpinia species in this study provided valuable genomic resources for further phylogeny and species identification in the family Zingiberaceae.

Background Zingiberoideae is a large and diverse subfamily of the family Zingiberaceae. Four genera in subfamily Zingiberoideae each possess 50 or more species, including Globba (100), Hedychium (> 80), Kaempferia (50) and Zingiber (150). Despite the agricultural, medicinal and horticultural importance of these species, genomic resources and suitable molecular markers for them are currently sparse. Results Here, we have sequenced, assembled and analyzed ten complete chloroplast genomes from nine species of subfamily Zingiberoideae: Globba lancangensis, Globba marantina, Globba multiflora, Globba schomburgkii, Globba schomburgkii var. angustata, Hedychium coccineum, Hedychium neocarneum, Kaempferia rotunda ‘Red Leaf’, Kaempferia rotunda ‘Silver Diamonds’ and Zingiber recurvatum. These ten chloroplast genomes (size range 162,630–163,968 bp) possess typical quadripartite structures that consist of a large single copy (LSC, 87,172–88,632 bp), a small single copy (SSC, 15,393–15,917 bp) and a pair of inverted repeats (IRs, 29,673–29,833 bp). The genomes contain 111–113 different genes, including 79 protein coding genes, 28–30 tRNAs and 4 rRNA genes. The dynamics of the genome structures, gene contents, amino acid frequencies, codon usage patterns, RNA editing sites, simple sequence repeats and long repeats exhibit similarities, with slight differences observed among the ten genomes. Further comparative analysis of seventeen related Zingiberoideae species, 12 divergent hotspots are identified. Positive selection is observed in 14 protein coding genes, including accD, ccsA, ndhA, ndhB, psbJ, rbcL, rpl20, rpoC1, rpoC2, rps12, rps18, ycf1, ycf2 and ycf4. Phylogenetic analyses, based on the complete chloroplast-derived single-nucleotide polymorphism data, strongly support that Globba, Hedychium, and Curcuma I + “the Kaempferia clade” consisting of Curcuma II, Kaempferia and Zingiber, form a nested evolutionary relationship in subfamily Zingiberoideae. Conclusions Our study provides detailed information on ten complete Zingiberoideae chloroplast genomes, representing a valuable resource for future studies that seek to understand the molecular evolutionary dynamics in family Zingiberaceae. The identified divergent hotspots can be used for development of molecular markers for phylogenetic inference and species identification among closely related species within four genera of Globba, Hedychium, Kaempferia and Zingiber in subfamily Zingiberoideae.

Zingiber montanum (Z. montanum) and Zingiber zerumbet (Z. zerumbet) are important medicinal and ornamental herbs in the genus Zingiber and family Zingiberaceae. Chloroplast-derived markers are useful for species identification and phylogenetic studies, but further development is warranted for these two Zingiber species. In this study, we report the complete chloroplast genomes of Z. montanum and Z. zerumbet, which had lengths of 164,464 bp and 163,589 bp, respectively. These genomes had typical quadripartite structures with a large single copy (LSC, 87,856-89,161 bp), a small single copy (SSC, 15,803-15,642 bp), and a pair of inverted repeats (IRa and IRb, 29,393-30,449 bp). We identified 111 unique genes in each chloroplast genome, including 79 protein-coding genes, 28 tRNAs and 4 rRNA genes. We analyzed the molecular structures, gene information, amino acid frequencies, codon usage patterns, RNA editing sites, simple sequence repeats (SSRs) and long repeats from the two chloroplast genomes. A comparison of the Z. montanum and Z. zerumbet chloroplast genomes detected 489 single-nucleotide polymorphisms (SNPs) and 172 insertions/deletions (indels). Thirteen highly divergent regions, including ycf1, rps19, rps18-rpl20, accD-psaI, psaC-ndhE, psbA-trnK-UUU, trnfM-CAU-rps14, trnE-UUC-trnT-UGU, ccsA-ndhD, psbC-trnS-UGA, start-psbA, petA-psbJ, and rbcL-accD, were identified and might be useful for future species identification and phylogeny in the genus Zingiber. Positive selection was observed for ATP synthase (atpA and atpB), RNA polymerase (rpoA), small subunit ribosomal protein (rps3) and other protein-coding genes (accD, clpP, ycf1, and ycf2) based on the Ka/Ks ratios. Additionally, chloroplast SNP-based phylogeny analyses found that Zingiber was a monophyletic sister branch to Kaempferia and that chloroplast SNPs could be used to identify Zingiber species. The genome resources in our study provide valuable information for the identification and phylogenetic analysis of the genus Zingiber and family Zingiberaceae.

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Compared with most flowers where the showy part comprises specialized leaves (petals) directly subtending the reproductive structures, most Zingiberaceae species produce showy “flowers” through modifications of leaves (bracts) subtending the true flowers throughout an inflorescence. Curcuma alismatifolia, belonging to the Zingiberaceae family, a plant species originating from Southeast Asia, has become increasingly popular in the flower market worldwide because of its varied and esthetically pleasing bracts produced in different cultivars. Here, we present the chromosome-scale genome assembly of C. alismatifolia “Chiang Mai Pink” and explore the underlying mechanisms of bract pigmentation. Comparative genomic analysis revealed C. alismatifolia contains a residual signal of whole-genome duplication. Duplicated genes, including pigment-related genes, exhibit functional and structural differentiation resulting in diverse bract colors among C. alismatifolia cultivars. In addition, we identified the key genes that produce different colored bracts in C. alismatifolia, such as F3′5'H, DFR, ANS and several transcription factors for anthocyanin synthesis, as well as chlH and CAO in the chlorophyll synthesis pathway by conducting transcriptomic analysis, bulked segregant analysis using both DNA and RNA data, and population genomic analysis. This work provides data for understanding the mechanism of bract pigmentation and will accelerate breeding in developing novel cultivars with richly colored bracts in C. alismatifolia and related species. It is also important to understand the variation in the evolution of the Zingiberaceae family.

The first complete chloroplast genome of Stahlianthus involucratus (Zingiberaceae) was reported in this study. The S. involucratus chloroplast genome was 163,300 bp in length and consisted of one large single copy (LSC) region of 87,498 bp, one small single copy (SSC) region of 15,568 bp, and a pair of inverted repeat (IR) regions 30,117 bp. It encoded 141 genes, including 87 protein-coding genes (79 PCG species), 46 tRNA genes (28 tRNA species) and 8 rRNA genes (4 rRNA species). The phylogenetic analysis based on single nucleotide polymorphisms strongly supported that S. involucratus, Curcuma roscoeana and Curcuma longa formed a cluster in group Curcuma II within family Zingiberaceae.

Caladium (Caladium × Hortulanum Birdsey) is a popular ornamental plant with a wide range of vibrant leaf color among Araceae. Even after years of breeding, creating new caladium leaf color variations is extremely difficult. Molecular marker‐assisted selection is an effective approach for accelerating breeding, but few studies on the molecular markers associated with caladium traits have been performed. In the current study, 144 caladium accessions were used to examine 12 phenotypic characteristics. The coefficient of variation for four numerical characters ranged from 23.94% to 43.22%, and the Shannon–Wiener indexes for eight descriptive characters ranged from 0.13 to 1.52. Based on L*, a*, b*, C, h° values determined by a colorimeter and hierarchical cluster analysis, the leaf color can be divided into four groups: pale green, green, light pink, and red. Furthermore, 7708 new SSR loci were identified by transcriptome sequencing, and 26 SSR markers with high polymorphism and reproducibility were screened. Genetic structure, NJ clustering, and PCoA analysis revealed that 144 accessions could be divided into three clusters, with genetic structure being closely related to germplasm origin. An association analysis revealed that the SSR markers 2, 1, 1, 1, 1, and 1 were mainly associated with petiole color, main vein color, blade upperside glossiness, and C, b*, and L* of leaf color (p < 0.01). These findings will serve as a valuable reference for evaluating germplasm resources and caladium molecular marker‐assisted breeding.