Comparative chloroplast genome analyses of cultivated and wild Capsicum species shed light on evolution and phylogeny.

The chloroplast (cp.) genome, also known as plastome, plays crucial roles in plant survival, adaptation, and evolution. The stable genetic structure of cp. genomes provides an ideal system for investigating species evolution. We sequenced three complete cp. genome sequences of Capsicum species and analyzed them using sequences of various Capsicum species retrieved from the NCBI database. The cp. genome of Capsicum species maintains a well-preserved quadripartite structure consisting of two inverted repeats (IRs) flanked by a large single copy (LSC) region and a small single copy (SSC) region. The sizes of cp. genome sequences ranged from 156,583 bp (C. lycianthoides) to 157,390 bp (C.pubescens). A total of 127-132 unique genes, including 83-87 protein-coding, 36-37 tRNA, and eight rRNA genes, were predicted. Comparison of cp. genomes of 10 Capsicum species revealed high sequence similarity in genome-wide organization and gene arrangements. Fragments of trnT-UGU/trnL-UAA, ccsA, ndhD, rps12, and ycf1 were identified as variable regions, and nucleotide variability of LSC and SSC was higher than that of IR. Phylogenetic speciation analysis showed that the major domesticated C. annuum species were the most extensively divergent species and closely related to C. tovarii and C. frutescens. Analysis of divergent times suggested that a substantial range of speciation events started occurring ~ 25.79 million years ago (Mya). Overall, comparative analysis of cp. genomes of Capsicum species not only offers new insights into their genetic variation and phylogenetic relationships, but also lays a foundation for evolutionary history, genetic diversity, conservation, and biological breeding of Capsicum species.

Genome-Wide SNP Markers for Genotypic and Phenotypic Differentiation of Melon (Cucumis melo L.) Varieties Using Genotyping-by-Sequencing.

Melon (Cucumis melo L.) is an economically important horticultural crop with abundant morphological and genetic variability. Complex genetic variations exist even among melon varieties and remain unclear to date. Therefore, unraveling the genetic variability among the three different melon varieties, muskmelon (C. melo subsp. melo), makuwa (C. melo L. var. makuwa), and cantaloupes (C. melo subsp. melo var. cantalupensis), could provide a basis for evolutionary research. In this study, we attempted a systematic approach with genotyping-by-sequencing (GBS)-derived single nucleotide polymorphisms (SNPs) to reveal the genetic structure and diversity, haplotype differences, and marker-based varieties differentiation. A total of 6406 GBS-derived SNPs were selected for the diversity analysis, in which the muskmelon varieties showed higher heterozygote SNPs. Linkage disequilibrium (LD) decay varied significantly among the three melon varieties, in which more rapid LD decay was observed in muskmelon (r2 = 0.25) varieties. The Bayesian phylogenetic tree provided the intraspecific relationships among the three melon varieties that formed, as expected, individual clusters exhibiting the greatest genetic distance based on the posterior probability. The haplotype analysis also supported the phylogeny result by generating three major networks for 48 haplotypes. Further investigation for varieties discrimination allowed us to detect a total of 52 SNP markers that discriminated muskmelon from makuwa varieties, of which two SNPs were converted into cleaved amplified polymorphic sequence markers for practical use. In addition to these markers, the genome-wide association study identified two SNPs located in the genes on chromosome 6, which were significantly associated with the phenotypic traits of melon seed. This study demonstrated that a systematic approach using GBS-derived SNPs could serve to efficiently classify and manage the melon varieties in the genebank.

Comparative Analysis of Polyphenolic Compounds in Different Amaranthus Species: Influence of Genotypes and Harvesting Year.

Amaranth is a nutritionally valuable crop, as it contains phenolic acids and flavonoids, yielding diverse plant secondary metabolites (PSMs) like phytosterol, tocopherols, and carotenoids. This study explored the variations in the contents of seventeen polyphenolic compounds within the leaves of one hundred twenty Amaranthus accessions representing nine Amaranthus species. The investigation entailed the analysis of phenolic content across nine Amaranthus species, specifically A. hypochondriacus, A. cruentus, A. caudatus, A. tricolor, A. dubius, A. blitum, A. crispus, A. hybridus, and A. viridis, utilizing ultra performance liquid chromatography with photodiode array detection (UPLC-PDA). The results revealed significant differences in polyphenolic compounds among accessions in which rutin content was predominant in all Amaranthus species in both 2018 and 2019. Among the nine Amaranthus species, the rutin content ranged from 95.72 ± 199.17 µg g-1 (A. dubius) to 1485.09 ± 679.51 µg g-1 (A. viridis) in 2018 and from 821.59 ± 709.95 µg g-1 (A. tricolor) to 3166.52 ± 1317.38 µg g-1 (A. hypochondriacus) in 2019. Correlation analysis revealed, significant positive correlations between rutin and kaempferol-3-O-ß-rutinoside (r = 0.93), benzoic acid and ferulic acid (r = 0.76), and benzoic acid and kaempferol-3-O-ß-rutinoside (r = 0.76), whereas gallic acid showed consistently negative correlations with each of the 16 phenolic compounds. Wide variations were identified among accessions and between plants grown in the two years. The nine species and one hundred twenty Amaranthus accessions were clustered into six groups based on their seventeen phenolic compounds in each year. These findings contribute to expanding our understanding of the phytochemical traits of accessions within nine Amaranthus species, which serve as valuable resources for Amaranthus component breeding and functional material development.

Identification of Vicia Species Native to South Korea Using Molecular and Morphological Characteristics.

Recently, within the Fabaceae family, the Vicia genus has been recognized for its vital role in sustainable agriculture. Vicia species are economically important grain and forage crops. However, the presence of complex morphological characteristics makes identification and recognition of native species difficult. In this study, the possibility of using DNA barcoding regions (ITS2, matK, and rbcL) to distinguish among 19 Vicia taxa (59 accessions) found in South Korea was evaluated. The sequence alignment analysis revealed considerable nucleotide diversity (π) between the loci, in which ITS2 showed the highest mean interspecific distance, whereas there was no intraspecific variability among the barcode regions in 12 of the 19 taxa. Phylogenetic analysis of combined barcoding regions revealed well-resolved phylogeny with the highest species level discrimination. Combinations of barcode loci were also used in classification at the subgenera and section levels. The results revealed that the combined barcoding regions can be used effectively to differentiate the following species: Vicia angustifolia var. segetilis, Vicia bungei, Vicia villosa, Vicia cracca, Vicia dasycarpa, Vicia hirsuta, Vicia tetrasperma, Vicia amurensis, Vicia hirticalycina, and Vicia chosenensis. However, it is difficult to differentiate the species of Vicia unijuga, Vicia unijuga var. kaussanensis, Vicia linearifolia, Vicia unijuga f. angustifolia, Vicia nipponica, Vicia amoena, Vicia venosa var. cuspidata, Vicia pseudo-orobus, and Vicia japonica with the tested barcode regions. These species come under sect. Vicilla and are found to be closely related or species that have recently undergone speciation; thus, it has limitation to distinguish with recommended barcodes. Hence, to differentiate the unclassified species, 39 morphological characteristics were investigated, in which 16 useful characteristics were selected for efficient classification. Finally, the 16 selected morphological useful traits efficiently differentiated all the Vicia species. In conclusion, a combination of barcoding loci together with morphological characteristics of this study efficiently discriminated all the Korean Vicia species.

Genetic Diversity and Population Structure of Potato Germplasm in RDA-Genebank: Utilization for Breeding and Conservation.

Potato (Solanum tuberosum L.) is an important staple food and economic crop in many countries. It is of critical importance to understand the genetic diversity and population structure for effective collection, conservation, and utilization of potato germplasm. Thus, the objective of the present study was to investigate the genetic diversity and population structure of potato germplasm conserved in the National Agrobiodiversity Center (NAC) of South Korea to provide basic data for future preservation and breeding of potato genetic resources. A total of 24 simple sequence repeat (SSR) markers were used to assess the genetic diversity and population structure of 482 potato accessions. A total of 257 alleles were detected, with an average of 10.71 alleles per locus. Analysis of molecular variance showed that 97% of allelic diversity was attributed to individual accessions within the population, while only 3% was distributed among populations. Results of genetic structure analysis based on STRUCTURE and discriminant analysis of principal components revealed that 482 potato accessions could be divided into two main subpopulations. Accessions of subpopulation 1 mainly belonged to cultivars and breeding lines. Accessions of subpopulations 2 basically corresponded to wild relatives of potatoes. Results of this study provide useful information for potato improvement and conservation programs, although further studies are needed for a more accurate evaluation of genetic diversity and phenotypic traits of potatoes.

Interspecific variation of seed morphological and micro-morphological traits in the genus Vicia (Fabaceae).

Seed macro- and micro-morphology were analyzed to evaluate their capacity to discriminate species in the genus Vicia (Fabaceae). To assess the interspecific variation of the taxa in the genus Vicia, 41 accessions were obtained from the USDA-ARS germplasm collection in the USA and 19 accessions were collected from Korea. Seed morphological characteristics such as shape, color, mottling, finish, length, width, diameter, hilum shape, hilum color, hilum length, and lens distance from the hilum were examined under a stereomicroscope. Testa texture characteristics such as testa pattern, papillae type, density, height, ribbing, surface deposits, and peaks topped with wax were examined under scanning electron microscopy. Various gross-morphological traits of seeds of Vicia species have been analyzed and compared. The present study revealed significant variation in testa traits. Testa were papillose and papillose with mounds, the latter being observed only in Vicia lathyroides. The present study revealed 20 key traits that could be used to diagnose Vicia species and classify them.

Genotyping-by-Sequencing Derived Single Nucleotide Polymorphisms Provide the First Well-Resolved Phylogeny for the Genus Triticum (Poaceae).

Wheat (Triticum spp.) has been an important staple food crop for mankind since the beginning of agriculture. The genus Triticum L. is composed of diploid, tetraploid, and hexaploid species, majority of which have not yet been discriminated clearly, and hence their phylogeny and classification remain unresolved. Genotyping-by-sequencing (GBS) is an easy and affordable method that allows us to generate genome-wide single nucleotide polymorphism (SNP) markers. In this study, we used GBS to obtain SNPs covering all seven chromosomes from 283 accessions of Triticum-related genera. After filtering low-quality and redundant SNPs based on haplotype information, the GBS assay provided 14,188 high-quality SNPs that were distributed across the A (71%), B (26%), and D (2.4%) genomes. Cluster analysis and discriminant analysis of principal components (DAPC) allowed us to distinguish six distinct groups that matched well with Triticum species complexity. We constructed a Bayesian phylogenetic tree using 14,188 SNPs, in which 17 Triticum species and subspecies were discriminated. Dendrogram analysis revealed that the polyploid wheat species could be divided into groups according to the presence of A, B, D, and G genomes with strong nodal support and provided new insight into the evolution of spelt wheat. A total of 2,692 species-specific SNPs were identified to discriminate the common (T. aestivum) and durum (T. turgidum) wheat cultivar and landraces. In principal component analysis grouping, the two wheat species formed individual clusters and the SNPs were able to distinguish up to nine groups of 10 subspecies. This study demonstrated that GBS-derived SNPs could be used efficiently in genebank management to classify Triticum species and subspecies that are very difficult to distinguish by their morphological characters.

Genetic Diversity Assessed by Genotyping by Sequencing (GBS) in Watermelon Germplasm.

Watermelon is an economically important vegetable fruit worldwide. The objective of this study was to conduct a genetic diversity of 68 watermelon accessions using single nucleotide polymorphisms (SNPs). Genotyping by sequencing (GBS) was used to discover SNPs and assess genetic diversity and population structure using STRUCTURE and discriminant analysis of principal components (DAPC) in watermelon accessions. Two groups of watermelons were used: 1) highly utilized 41 watermelon accessions at the National Agrobiodiversity Center (NAC) at the Rural Development Administration in South Korea; and 2) 27 Korean commercial watermelons. Results revealed the presence of four clusters within the populations differentiated principally based on seed companies. In addition, there was higher genetic differentiation among commercial watermelons of each company. It is hypothesized that the results obtained from this study would contribute towards the expansion of this crop as well as providing data about genetic diversity, which would be useful for the preservation of genetic resources or for future breeding programs.

The complete chloroplast genome sequence of wild oat, Avena sterilis L. (Poaceae) and its phylogeny.

Wild oat, Avena sterilis L. is a stout broad-leaved annual grass resembling cultivated oats in general appearance. In this study, we sequenced the complete chloroplast (cp) genome sequence of A. sterilis for the first time to investigate their phylogenetic relationship in the family Poaceae. The complete cp genome sequence is 135,887 bp in length with 38.5% overall GC content and exhibits a typical quadripartite structure comprising one pair of inverted repeats (21,603 bp) separated by a small single-copy region (12,575 bp) and a large single-copy region (80,106). The cp genome encodes 111 unique genes, 76 of which are protein-coding genes, four rRNA genes, 30 tRNA genes, and 18 duplicated genes in the inverted repeat region. The phylogenetic analysis indicated A. sterilis closely clustered with the cultivated oat, A. sativa L.

The complete chloroplast genome sequences of little millet (Panicum sumatrense Roth ex Roem. and Schult.) (Poaceae).

Little millet, Panicum sumatrense Roth ex Roem. & Schult., is an important cultivated species under the tribe Paniceae, sub-family Panicoideae and family Poaceae. In this study, for the first time we sequenced the complete chloroplast (cp) genome of P. sumatrense to investigate their phylogenetic relationship in the family Poaceae. The complete cp genome sequence of P. sumatrense is 139,384 bp in length with 38.6% overall GC content and exhibits a typical quadripartite structure comprising one pair of inverted repeats (22,723 bp) separated by a small single-copy region (12,583 bp) and a large single-copy region (81,355 bp). The P. sumatrense cp genome encodes 125 unique genes, which include 91 protein-coding genes, 4 rRNA genes, 30 tRNA genes, and 20 genes were duplicated in the inverted repeat region. This newly determined cp genome (P. sumatrense) could be valuable information for the breeding programs of this cereal crops in the family Poaceae.