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Stenocereus thurberi is a columnar cactus distributed in northwestern Mexico. Its study has focused on the phenology of the cactus and not on its fruit, called pitaya. The pitaya contains pigments, such as betalains, which are important bioactive compounds for their antioxidant capacity. Therefore, the extraction of betalains from pitaya pulp is an important step in providing information for the subsequent study and development of functional foods, nutraceuticals, colorants, and cosmetics. The objective of this study was to optimize the betalain extraction process from pitaya pulp ( Stenocereus thurberi ) in water and to evaluate its antioxidant capacity before and after its optimization using response surface methodology. In this study, a three-factor, three-level composite central design (CCD) with four center points was used to assess the influence of temperature, solvent volume, and sonication time on betalain extraction from pitaya pulp. Optimal extraction conditions were found using 57 °C, 34 mL of solvent, and 27 min of sonication. The total betalain content under optimal conditions was 2.6 mg/g of dry sample. The combination of the three factors showed high antioxidant activity by DPPH and ABTS. The conditions optimized for the extraction of betalains from the pitaya pulp in water by ultrasound did not affect its antioxidant capacity. Therefore, these conditions can be efficiently applied to extract betalains from pitaya pulp on a large scale as a promising alternative to replace synthetic dyes.

Bats are the main pollinators and seed dispersers of Stenocereus thurberi, a xenogamous columnar cactus of northwestern Mexico and a good model to illustrate spatial dynamics of gene flow in long-lived species. Previous studies in this cactus showed differences among populations in the type and abundance of pollinators, and in the timing of flowering and fruiting. In this study we analyzed genetic variability and population differentiation among populations. We used three primers of ISSR to analyze within and among populations genetic variation from eight widely separated populations of S. thurberi in Sonora, Mexico. Sixty-six out of 99 of the ISSR bands (P = 66.7%) were polymorphic. Total heterozygosity for all populations sampled revealed high genetic diversity (Hsp = 0.207, HBT = 0.224). The AMOVA showed that most of the genetic variation was within populations (80.5%). At the species level, estimates of population differentiation, [theta] = 0.175 and [theta] B = 0.194, indicated moderate gene flow among populations. The absence of a significant correlation between genetic and geographic distances indicated little isolation by geographic distance. The large genetic variation and diversity found in S. thurberi is consistent with its open reproductive system and the high mobility of bats, a major pollinator. However, small changes in number or kind of pollinators and seed dispersal agents, in the directionality of migratory routes, and/or in the timing of flowering and fruiting among populations, can critically affect gene flow dynamics.

Few clades of plants have proven as difficult to classify as cacti. One explanation may be an unusually high level of convergent and parallel evolution (homoplasy). To evaluate support for this phylogenetic hypothesis at the molecular level, we sequenced the genomes of four cacti in the especially problematic tribe Pachycereeae, which contains most of the large columnar cacti of Mexico and adjacent areas, including the iconic saguaro cactus (Carnegiea gigantea) of the Sonoran Desert. We assembled a high-coverage draft genome for saguaro and lower coverage genomes for three other genera of tribe Pachycereeae (Pachycereus, Lophocereus, and Stenocereus) and a more distant outgroup cactus, Pereskia. We used these to construct 4,436 orthologous gene alignments. Species tree inference consistently returned the same phylogeny, but gene tree discordance was high: 37% of gene trees having at least 90% bootstrap support conflicted with the species tree. Evidently, discordance is a product of long generation times and moderately large effective population sizes, leading to extensive incomplete lineage sorting (ILS). In the best supported gene trees, 58% of apparent homoplasy at amino sites in the species tree is due to gene tree-species tree discordance rather than parallel substitutions in the gene trees themselves, a phenomenon termed “hemiplasy.” The high rate of genomic hemiplasy may contribute to apparent parallelisms in phenotypic traits, which could confound understanding of species relationships and character evolution in cacti.

BACKGROUND AND AIMS: Ethnobotanical studies in Mexico have documented that Mesoamerican peoples practise systems of in situ management of wild and weedy vegetation directed to control availability of useful plants. In situ management includes let standing, encouraging growing and protection of individual plants of useful species during clearance of vegetation, which in some cases may involve artificial selection. The aim of this study was to review, complement and re-analyse information from three case studies which examined patterns of morphological, physiological and genetic effects of artificial selection in plant populations under in situ management in the region. METHODS: Information on wild and in situ managed populations of the herbaceous weedy plants Anoda cristata and Crotalaria pumila, the tree Leucaena esculenta subsp. esculenta and the columnar cacti Escontria chiotilla, Polaskia chichipe and Stenocereus stellatus from Central Mexico was re-analysed. Analyses compared morphology and frequency of morphological variants, germination patterns, and population genetics parameters between wild and managed in situ populations of the species studied. Species of columnar cacti are under different management intensities and their populations, including cultivated stands of P. chichipe and S. stellatus, were also compared between species. KEY RESULTS: Significant differences in morphology, germination patterns and genetic variation documented between wild, in situ managed and cultivated populations of the species studied are associated with higher frequencies of phenotypes favoured by humans in managed populations. Genetic diversity in managed populations of E. chiotilla and P. chichipe is slightly lower than in wild populations but in managed populations of S. stellatus variation was higher than in the wild. However, genetic distance between populations was generally small and influenced more by geographic distance than by management. CONCLUSIONS: Artificial selection operating on in situ managed populations of the species analysed is causing incipient domestication. This process could be acting on any of the 600-700 plant species documented to be under in situ management in Mesoamerica. In situ domestication of plants could be relevant to understand early processes of domestication and current conditions of in situ conservation of plant genetic resources.

Betalains of pitaya (Stenocereus pruinosus) fruit can be used as natural pigment, but they are susceptible to deterioration by temperature, pH, and presence of sugars. In this work, a refined extract (Er) of betalains was obtained through aqueous two-phase extraction, which reduced significantly sugar and mucilage contents. In order to favor stability, the encapsulation of the refined extract was evaluated, with native potato starch that was modified through phosphorylation or succinylation and reactive extrusion. Starches were evaluated in terms of degree of substitution, Fourier transform infrared spectroscopy, scanning electron microscopy, and viscous behavior. Microcapsules were formed by spray drying and their stability was evaluated at 40 °C for 39 days and by using them as pigmenting agent of yogurt at 4 °C during 32 days. The behavior of modified starches during encapsulation was superior to that of commercial N-Lok® starch. Microcapsules based on modified starches showed better pigmenting potential and higher stability than Er and microcapsules based on N-Lok® starch. The separation of betalains from pitaya fruit may be a good alternative for adding value to this plant genetic resource.

Stenocereus stellatus is one of the 10 species of cactus of greatest economic importance in Mexico, although its fruits contain bioactive components such betalains and phenolic compounds, which in turn cause multiple positive pharmacological effects on health, very little has been explored. This study aimed to employ a response surface methodology (RSM) approach to optimize the extraction conditions for maximizing the concentration of betalains (betacyanins and betaxanthins), total phenolic compounds (TPC), and antioxidant capacity (AC). To optimize the extraction of betalains, pH ( W ), extraction temperature ( X ), extraction time ( Y ), and water:ethanol solvent ratio ( Z ) were evaluated. For TPC and AC, the same factors were evaluated, except Z . All these factors influenced on the concentration of betalains. The optimal extraction conditions were found to be pH 4.2, extraction temperature of 10 °C, extraction time of 60 min, and a water:ethanol solvent ratio of 55%, and under these conditions, 0.51 mg per g total betalains (BT) were obtained, of which 0.25 mg per g corresponded to BC and 0.26 mg per g to BX. In TPC and AC, only pH and temperature affected these determinations. The optimal conditions for both variables were pH of 4 and extraction temperature of 60 °C, and under these conditions, 2.34 mg of gallic acid equivalents per g and 18.60 µmol of Trolox equivalents per g were obtained. The results suggest that Stenocereus stellatus could be a promising source for these compounds, which have potential applications in the food and pharmaceutical industries due to their excellent stability under these conditions.

Genus Stenocereus (Cactaceae) is formed by about 23 species, most of them under different type and intensity of management, including forms of silvicultural management and cultivation. Some management types involve domestication processes; previous studies have demonstrated that management determines significant effect increasing frequency of phenotypes favorable to humans in silvicultural managed and cultivated populations. Effects of management on genetic variation have been documented to increase variation in some populations and to decrease in others, but its effect on genetic differentiation between wild and domesticated populations remains unclear. In this study, we evaluate the genetic variation of four species forming the Stenocereus griseus complex (SGSC), the differentiation among populations of species under different management and phylogeographic patterns of the complex. We analyzed population genetics through nine microsatellites and phylogeography by two nuclear regions. Genetic differentiation was higher within than among populations, management therefore accounting for low attributable variance. We identified a genetic spatial pattern of maximum genetic diversity in southern Mexico ( Stenocereus pruinosus ) dropping down to minimum values in Northern Mexico ( S. huastecorum ). Phylogeography showed a bottleneck in S. huastecorum and a close relationship between S. laevigatus and S. griseus . We found that genetic diversity and differentiation of the SGSC is associated to spatial factors rather than to management. The discordance between patterns of phenotypic differentiation previously reported and the low or null genetic differentiation can be explained because the neutral markers are not correlated with human selected traits. Use of NGS and genomic approaches could provide a different panorama of genetic variation and differentiation associated to management.

Stenocereus thurberi is an endemic species in northwestern Mexico. It produces colorful fruits called pitayas that have an edible pulp. They have phytochemical compounds associated with biological activities. Ultrafiltration is a widely used method for the clarification of fruit juices and the recovery of phytochemicals. However, its effect has not been extensively studied in extracts. Therefore, the objective of this work is to study the effect of the ultrafiltration of pitaya extract (Stenocereus thurberi) on its phytochemical content, antioxidant capacity, and identification of phenolic compounds by UPLC-DAD-MS, providing greater knowledge about the pitaya. In this study, two extracts were analyzed, the unclarified extract (UE) and the clarified extract (CE). The antioxidant capacity was higher in the CE with 15.93 ± 0.42 mM TE/g, DPPH and 18.37 ± 0.016 mM TE/g, ABTS. The UPLC-MS analysis indicated the decrease in phenolic compounds in the CE and the presence of gallic acid and resorcinol, compounds that had not been identified in other species of Stenocereus spp. The correlation analysis indicated that all the phytochemicals present in the pitaya contribute significantly to the antioxidant capacity. The ultrafiltration process could be a viable option to improve the biological activity of the natural extracts.

Stenocereus queretaroensis fruits are endemic to Mexico. They have an excellent advantage in cultivation because they require little water and fertilizers. These plants do not require fungicides and herbicides, drastically reducing production costs. However, the nutritional contribution and potential health benefits of S. queretaroensis fruits are unknown. The physicochemical characterization, the content of bioactive compounds, and the antioxidant capacity (AOX) of four S. queretaroensis fruits (red, purple, yellow, and white) were evaluated. All fruits had a low sugar content (7.04–8.96%) and provided 4–5% dietary fiber. The purple and red fruits presented 19.7–20.29 mg/100 g fresh weight (fw) of total betalains, respectively, while the yellow fruit presented 9.21 mg/100 g fw of total carotenoids. The total soluble phenols were 54.86–62.14 mg/100 g fw. Flavonoids, hydroxycinnamic, and hydroxybenzoic acids were also found in all fruits in ascending order. The red fruit exhibited the highest AOX, followed by the yellow, purple, and white fruits. In conclusion, these fruits are a rich source of antioxidants and nutrients, highlighting that they provide 20% of daily consumption of dietary fiber and have a low caloric content. S. queretaroensis fruits, therefore, may have a high potential functionality, especially in people with diabetes and living with obesity.

BACKGROUND AND AIMS: The Tehuacán Valley in Mexico is a principal area of plant domestication in Mesoamerica. There, artificial selection is currently practised on nearly 120 native plant species with coexisting wild, silvicultural and cultivated populations, providing an excellent setting for studying ongoing mechanisms of evolution under domestication. One of these species is the columnar cactus Stenocereus pruinosus, in which we studied how artificial selection is operating through traditional management and whether it has determined morphological and genetic divergence between wild and managed populations. METHODS: Semi-structured interviews were conducted with 83 households of three villages to investigate motives and mechanisms of artificial selection. Management effects were studied by comparing variation patterns of 14 morphological characters and population genetics (four microsatellite loci) of 264 plants from nine wild, silvicultural and cultivated populations. KEY RESULTS: Variation in fruit characters was recognized by most people, and was the principal target of artificial selection directed to favour larger and sweeter fruits with thinner or thicker peel, fewer spines and pulp colours others than red. Artificial selection operates in agroforestry systems favouring abundance (through not felling plants and planting branches) of the preferred phenotypes, and acts more intensely in household gardens. Significant morphological divergence between wild and managed populations was observed in fruit characters and plant vigour. On average, genetic diversity in silvicultural populations (HE = 0·743) was higher than in wild (HE = 0·726) and cultivated (HE = 0·700) populations. Most of the genetic variation (90·58 %) occurred within populations. High gene flow (NmFST > 2) was identified among almost all populations studied, but was slightly limited by mountains among wild populations, and by artificial selection among wild and managed populations. CONCLUSIONS: Traditional management of S. pruinosus involves artificial selection, which, despite the high levels of gene flow, has promoted morphological divergence and moderate genetic structure between wild and managed populations, while conserving genetic diversity.