Domestication of a Mesoamerican cultivated fruit tree, Spondias purpurea.
ABSTRACT: Contemporary patterns of genetic variation in crops reflect historical processes associated with domestication, such as the geographic origin(s) of cultivated populations. Although significant progress has been made in identifying several global centers of domestication, few studies have addressed the issue of multiple origins of cultivated plant populations from different geographic regions within a domestication center. This study investigates the domestication history of jocote (Spondias purpurea), a Mesoamerican cultivated fruit tree. Sequences of the chloroplast spacer trnG-trnS were obtained for cultivated and wild S. purpurea trees, two sympatric taxa (Spondias mombin var. mombin and Spondias radlkoferi), and two outgroups (S. mombin var. globosa and Spondias testudinus). A phylogeographic approach was used and statistically significant associations of clades and geographical location were tested with a nested clade analysis. The sequences confirm that wild populations of S. purpurea are the likely progenitors of cultivated jocote trees. This study provides phylogeographic evidence of multiple domestications of this Mesoamerican cultivated fruit tree. Haplotypes detected in S. purpurea trees form two clusters, each of which includes alleles recovered in both cultivated and wild populations from distinct geographic regions. Cultivated S. purpurea populations have fewer unique trnG-trnS alleles than wild populations; however, five haplotypes were absent in the wild. The presence of unique alleles in cultivation may reflect contemporary extinction of the tropical dry forests of Mesoamerica. These data indicate that some agricultural habitats may be functioning as reservoirs of genetic variation in S. purpurea.
Project description:This study reports the complete chloroplast sequences of three Spondias species. The genome sequences were obtained for Spondias tuberosa, Spondias bahienses, and Spondias mombin using the Illumina sequencing technology by a combination of de novo methods and a reference-guided assembly using Sapindus mukorossi as reference. The genomes of S. tuberosa, S. bahiensis, and S. mombin had 162,036, 162,218, and 162,302 bp, respectively. The coding regions exhibited 130 genes, including 34-35 tRNAs and 4 rRNAs. The results revealed synteny among the genomes, with high conservation in the gene order and content and CG content. The inverted repeat regions (IRA and IRB) and the large and small single copies were very similar among the three genomes. The phylogenomic analysis reported similar topologies as that of previous studies, which used partial chloroplast, wherein S. mombin was the first diverging lineage, while S. tuberosa and S. bahiensis were derived, indicating that the phylogenetic analysis using partial or complete genome produces similar results. In summary, (1) we presented the first complete chloroplast genome for the genus Spondias, (2) phylogenies analyzed using the complete chloroplast genomes revealed a robust phylogenetic topology for Spondias, and (3) gene order, content, and orientation in Spondias are highly conserved.
Project description:Domestication is a continuous evolutionary process guided by humans. This process leads to divergence in characteristics such as behaviour, morphology or genetics, between wild and managed populations. Agaves have been important resources for Mesoamerican peoples since prehistory. Some species are domesticated and others vary in degree of domestication. Agave inaequidens Koch is used in central Mexico to produce mescal, and a management gradient from gathered wild and silvicultural populations, as well as cultivated plantations, has been documented. Significant morphological differences were reported among wild and managed populations, and a high phenotypic variation in cultivated populations composed of plants from different populations. We evaluated levels of genetic diversity and structure associated with management, hypothesizing that high morphological variation would be accompanied by high genetic diversity in populations with high gene flow and low genetic structure among managed and unmanaged populations. Wild, silvicultural and cultivated populations were studied, collecting tissue of 19-30 plants per population. Through 10 nuclear microsatellite loci, we compared population genetic parameters. We analysed partition of variation associated with management categories to estimate gene flow among populations. Agave inaequidens exhibits high levels of genetic diversity (He = 0.707) and moderate genetic structure (FST = 0.112). No differences were found in levels of genetic diversity among wild (He = 0.704), silviculturally managed (He = 0.733) and cultivated (He = 0.698) populations. Bayesian analysis indicated that five genetic clusters best fit the data, with genetic groups corresponding to habitats where populations grow rather than to management. Migration rates ranged from zero between two populations to markedly high among others (M = 0.73-35.25). Natural mechanisms of gene flow and the dynamic management of agave propagules among populations favour gene flow and the maintenance of high levels of variation within all populations. The slight differentiation associated with management indicates that domestication is in an incipient stage.
Project description:<i>Anastrepha obliqua</i> (Macquart) (Diptera: Tephritidae) is an important pest in the neotropical region. It is considered a polyphagous insect, meaning it infests plants of different taxonomic families and readily colonizes new host plants. The change to new hosts can lead to diversification and the formation of host races. Previous studies investigating the effect of host plants on population structure and selection in <i>Anastrepha obliqua</i> have focused on the use of data from the mitochondrial DNA sequence and microsatellite markers of nuclear DNA, and there are no analyses at the genomic level. To better understand this issue, we used a pooled restriction site-associated DNA sequencing (pooled RAD-seq) approach to assess genomic differentiation and population structure across sympatric populations of <i>Anastrepha obliqua</i> that infest three host plants-<i>Spondias purpurea</i> (red mombin), <i>Mangifera indica</i> (mango) of the family Anacardiaceae and <i>Averrhoa carambola</i> (carambola) of the family Oxalidaceae-in sympatric populations of the species <i>Anastrepha obliqua</i> of Inter-Andean Valley of the Cauca River in southwestern Colombia. Our results show genomic differentiation of populations from carambola compared to mango and red mombin populations, but the genetic structure was mainly established by geography rather than by the host plant. On the other hand, we identified 54 SNPs in 23 sequences significantly associated with the use of the host plant. Of these 23 sequences, we identified 17 candidate genes and nine protein families, of which four protein families are involved in the nutrition of these flies. Future studies should investigate the adaptive processes undergone by phytophagous insects in the Neotropics, using fruit flies as a model and state-of-the-art molecular tools.
Project description:<i>Spondias</i> species have been used in traditional medicine for different human ailments. In this study, the effect of different solvents (ethyl acetate, methanol, and water) and extraction methods (infusion, maceration, and Soxhlet extraction) on the enzyme inhibitory activity against acetylcholinesterase, butyrylcholinesterase, tyrosinase, α-amylase, α-glucosidase, and antioxidant properties of <i>S. mombin</i> and <i>S. dulcis</i> leaves and stem bark were evaluated. Ultra-high-performance liquid chromatography-high resolution mass spectrometry (UHPLC-HRMS) yield in the identification and/or annotation of 98 compounds showing that the main secondary metabolites of the plant are gallic and ellagic acids and their derivatives, ellagitannins, hydroxybenzoic, hydroxycinnamic, acylquinic acids and flavonols, flavanones, and flavanonols. The leaves infusion of both <i>Spondias</i> species showed highest inhibition against acetylcholinesterase (AChE) (10.10 and 10.45 mg galantamine equivalent (GALAE)/g, for <i>S. dulcis</i> and <i>S. mombin</i>, respectively). The ethyl acetate extracts of the stem bark of <i>S. mombin</i> and <i>S. dulcis</i> actively inhibited α-glucosidase. Methanolic extracts of the leaves and stem bark exhibited highest tyrosinase inhibitory action. Antioxidant activity and higher levels of phenolics were observed for the methanolic extracts of <i>Spondias.</i> The results suggested that the <i>Spondias</i> species could be considered as natural phyto-therapeutic agents in medicinal and cosmeceutical applications.
Project description:Perennial forms of Gossypium hirsutum are classified under seven races. Five Mesoamerican races would have been derived from the wild race 'yucatanense' from northern Yucatán. 'Marie-Galante', the main race in the Caribbean, would have developed from introgression with G. barbadense. The racial status of coastal populations from the Caribbean has not been clearly defined. We combined Ecological Niche Modeling with an analysis of SSR marker diversity, to elucidate the relationships among cultivated, feral and wild populations of perennial cottons. Out of 954 records of occurrence in Mesoamerica and the Caribbean, 630 were classified into four categories cultivated, feral (disturbed and secondary habitats), wild/feral (protected habitats), and truly wild cotton (TWC) populations. The widely distributed three first categories cannot be differentiated on ecological grounds, indicating they mostly belong to the domesticated pool. In contrast, TWC are restricted to the driest and hottest littoral habitats, in northern Yucatán and in the Caribbean (from Venezuela to Florida), as confirmed by their climatic envelope in the factorial analysis. Extrapolating this TWC climatic model to South America and the Pacific Ocean points towards places where other wild representatives of tetraploid Gossypium species have been encountered. The genetic analysis sample comprised 42 TWC accessions from 12 sites and 68 feral accessions from 18 sites; at nine sites, wild and feral accessions were collected in close vicinity. Principal coordinate analysis, neighbor joining, and STRUCTURE consistently showed a primary divergence between TWC and feral cottons, and a secondary divergence separating 'Marie-Galante' from all other feral accessions. This strong genetic structure contrasts strikingly with the absence of geographic differentiation. Our results show that TWC populations of Mesoamerica and the Caribbean constitute a homogenous gene pool. Furthermore, the relatively low genetic divergence between the Mesoamerican and Caribbean domesticated pools supports the hypothesis of domestication of G. hirsutum in northern Yucatán.
Project description:Plant domestication can be seen as a long-term process that involves a complex interplay among demographic processes and evolutionary forces. Previous studies have suggested two domestication scenarios for Lima bean in Mesoamerica: two separate domestication events, one from gene pool MI in central-western Mexico and another one from gene pool MII in the area Guatemala-Costa Rica, or a single domestication from gene pool MI in central-western Mexico followed by post-domestication gene flow with wild populations. In this study we evaluated the genetic structure of the wild gene pool and tested these two competing domestication scenarios of Lima bean in Mesoamerica by applying an ABC approach to a set of genome-wide SNP markers. The results confirm the existence of three gene pools in wild Lima bean, two Mesoamerican gene pools (MI and MII) and the Andean gene pool (AI), and suggest the existence of another gene pool in central Colombia. The results indicate that although both domestication scenarios may be supported by genetic data, higher statistical support was given to the single domestication scenario in central-western Mexico followed by admixture with wild populations. Domestication would have involved strong founder effects reflected in loss of genetic diversity and increased LD levels in landraces. Genomic regions affected by selection were detected and these may harbor candidate genes related to domestication.
Project description:The runner bean is a legume species from Mesoamerica closely related to common bean (Phaseolus vulgaris). It is a perennial species, but it is usually cultivated in small-scale agriculture as an annual crop for its dry seeds and edible immature pods. Unlike the common bean, P. coccineus has received little attention from a genetic standpoint. In this work we aim to (1) provide information about the domestication history and domestication events of P. coccineus; (2) examine the distribution and level of genetic diversity in wild and cultivated Mexican populations of this species; and, (3) identify candidate loci to natural and artificial selection. For this, we generated genotyping by sequencing data (42,548 SNPs) from 242 individuals of P. coccineus and the domesticated forms of the closely related species P. vulgaris (20) and P. dumosus (35). Eight genetic clusters were detected, of which half corresponds to wild populations and the rest to domesticated plants. The cultivated populations conform a monophyletic clade, suggesting that only one domestication event occurred in Mexico, and that it took place around populations of the Trans-Mexican Volcanic Belt. No difference between wild and domesticated levels of genetic diversity was detected and effective population sizes are relatively high, supporting a weak genetic bottleneck during domestication. Most populations presented an excess of heterozygotes, probably due to inbreeding depression. One population of P. coccineus subsp. striatus had the greatest excess and seems to be genetically isolated despite being geographically close to other wild populations. Contrasting with previous studies, we did not find evidence of recent gene flow between wild and cultivated populations. Based on outlier detection methods, we identified 24 domestication-related SNPs, 13 related to cultivar diversification and eight under natural selection. Few of these SNPs fell within annotated loci, but the annotated domestication-related SNPs are highly expressed in flowers and pods. Our results contribute to the understanding of the domestication history of P. coccineus, and highlight how the genetic signatures of domestication can be substantially different between closely related species.
Project description:This study investigated the quantitative polyphenolic constituents and gastroprotective effects of aqueous leaf extracts of <i>Spondias mombin</i> and <i>Ficus exasperata</i> against indomethacin-induced gastric ulcer in rats. Ulceration was induced by a single oral administration of indomethacin (30 mg/kg body weight). Wistar rats were pretreated with esomeprazole (reference drug) at a dose of 20 mg/kg body weight, <i>S. mombin</i> or <i>F. exasperata</i> at 100 and 200 mg/kg body weight once daily for 21 days prior to ulcer induction. At the end of the experiment, gastric secretions and antioxidant parameters were evaluated. We observed that the significantly increased (<i>p</i> < 0.05) ulcer index, gastric volume, malondialdehyde level and pepsin activity were effectively reduced following treatment with <i>S. mombin</i> and <i>F. exasperata</i>. The extracts also markedly attenuated the reduced activity of superoxide dismutase as well as pH and mucin content in the ulcerated rats. These findings are indicative of gastroprotective and antioxidative potentials of the extracts which is also evident in the degree of % inhibition against ulceration. The available data in this study suggest that the extracts of <i>S. mombin</i> and <i>F. exasperata</i> proved to be capable of ameliorating indomethacin-induced gastric ulceration and the probable mechanisms are via antioxidative and proton pump inhibition.
Project description:The origin and domestication of cultivated barley have long been under debate. A population-based resequencing and phylogenetic analysis of the single copy of RPB2 gene was used to address barley domestication, to explore genetic differentiation of barley populations on the worldwide scale, and to understand gene-pool exchanges during the spread and subsequent development of barley cultivation. Our results revealed significant genetic differentiation among three geographically distinct wild barley populations. Differences in haplotype composition among populations from different geographical regions revealed that modern cultivated barley originated from two major wild barley populations: one from the Near East Fertile Crescent and the other from the Tibetan Plateau, supporting polyphyletic origin of cultivated barley. The results of haplotype frequencies supported multiple domestications coupled with widespread introgression events that generated genetic admixture between divergent barley gene pools. Our results not only provide important insight into the domestication and evolution of cultivated barley, but also enhance our understanding of introgression and distinct selection pressures in different environments on shaping the genetic diversity of worldwide barley populations, thus further facilitating the effective use of the wild barley germplasm.