Management, morphological and genetic diversity of domesticated agaves in Michoacán, México

Stem transcriptome screen for selection in wild and cultivated pitahaya (Selenicereus undatus): an epiphytic cactus with edible fruit

Dragon fruit, pitahaya or pitaya are common names for the species in the Hylocereus group of Selenicereus that produce edible fruit. These Neotropical epiphytic cacti are considered promising underutilized crops and are currently cultivated around the world. The most important species, S. undatus, has been managed in the Maya domain for centuries and is the focus of this article. Transcriptome profiles from stems of wild and cultivated plants of this species were compared. We hypothesized that differences in transcriptomic signatures could be associated with genes related to drought stress. De novo transcriptome assembly and the analysis of differentially expressed genes (DEGs) allowed us to identify a total of 9,203 DEGs in the Hunucmá cultivar relative of wild Mozomboa plants. Of these, 4,883 represent up-regulated genes and 4,320, down-regulated genes. Additionally, 6,568 DEGs were identified from a comparison between the Umán cultivar and wild plants, revealing 3,286 up-regulated and 3,282 down-regulated genes. Approximately half of the DEGs are shared by the two cultivated plants. Differences between the two cultivars that were collected in the same region could be the result of differences in management. Metabolism was the most representative functional category in both cultivars. The up-regulated genes of both cultivars formed a network related to the hormone-mediated signaling pathway that includes cellular responses to auxin stimulus and to hormone stimulus. These cellular reactions have been documented in several cultivated plants in which drought-tolerant cultivars modify auxin transport and ethylene signaling, resulting in a better redistribution of assimilates.

Uses, Knowledge and Extinction Risk Faced by Agave Species in Mexico

We compiled an updated database of all Agave species found in Mexico and analyzed it with specific criteria according to their biological parameters to evaluate the conservation and knowledge status of each species. Analyzing the present status of all Agave species not only provides crucial information for each species, but also helps determine which ones require special protection, especially those which are heavily used or cultivated for the production of distilled beverages. We conducted an extensive literature review search and compiled the conservation status of each species using mainstream criteria by IUCN. The information gaps in the database indicate a lack of knowledge and research regarding specific Agave species and it validates the need to conduct more studies on this genus. In total, 168 Agave species were included in our study, from which 89 are in the subgenus Agave and 79 in the subgenus Littaea. Agave lurida and A. nizandensis, in the subgenus Agave and Littaea, respectively, are severely endangered, due to their endemism, lack of knowledge about pollinators and floral visitors, and their endangered status according to the IUCN Red List. Some species are at risk due to the loss of genetic diversity resulting from production practices (i.e., Agave tequilana), and others because of excessive and unchecked overharvesting of wild plants, such as A. guadalajarana, A. victoriae-reginae, A. kristenii, and others. Given the huge economic and ecological importance of plants in the genus Agave, our review will be a milestone to ensure their future and continued provision of ecosystem services for humans, as well as encouraging further research in Agave species in an effort to enhance awareness of their conservation needs and sustainable use, and the implementation of eco-friendly practices in the species management.

Conservation genomics of Agave tequilana Weber var. azul: low genetic differentiation and heterozygote excess in the tequila agave from Jalisco, Mexico

Background

Genetic diversity is fundamental for the survival of species. In particular, in a climate change scenario, it is crucial that populations maintain genetic diversity so they can adapt to novel environmental conditions. Genetic diversity in wild agaves is usually high, with low genetic differentiation among populations, in part maintained by the agave pollinators such as the nectarivorous bats. In cultivated agaves, patterns of genetic diversity vary according to the intensity of use, management, and domestication stage. In Agave tequilana Weber var. azul (A. tequilana thereafter), the plant used for tequila production, clonal propagation has been strongly encouraged. These practices may lead to a reduction in genetic diversity.

Methods

We studied the diversity patterns with genome-wide SNPs, using restriction site associated DNA sequencing in cultivated samples of A. tequilana from three sites of Jalisco, Mexico. For one locality, seeds were collected and germinated in a greenhouse. We compared the genomic diversity, levels of inbreeding, genetic differentiation, and connectivity among studied sites and between adults and juvenile plants.

Results

Agave tequilana presented a genomic diversity of H_T = 0.12. The observed heterozygosity was higher than the expected heterozygosity. Adults were more heterozygous than juveniles. This could be a consequence of heterosis or hybrid vigor. We found a shallow genetic structure (average paired F_ST = 0.0044). In the analysis of recent gene flow, we estimated an average migration rate among the different populations of m = 0.25. In particular, we found a population that was the primary source of gene flow and had greater genomic diversity (H_E and H_O ), so we propose that this population should continue to be monitored as a potential genetic reservoir.

Discussion

Our results may be the consequence of more traditional management in the studied specific region of Jalisco. Also, the exchange of seeds or propagules by producers and the existence of gene flow due to occasional sexual reproduction may play an important role in maintaining diversity in A. tequilana. For populations to resist pests, to continue evolving and reduce their risk of extinction under a climate change scenario, it is necessary to maintain genetic diversity. Under this premise we encourage to continue acting in conservation programs for this species and its pollinators.

Agave Fructans in Oaxaca’s Emblematic Specimens: Agave angustifolia Haw. and Agave potatorum Zucc

Despite the recognition of Agave tequilana Weber var. Azul as raw material for producing tequila and obtaining prebiotics, there are other highly relevant Agave species in Mexico. Oaxaca contains a startlingly diverse range of Agave species; Agave angustifolia Haw. and Agave potatorum Zucc. are two classic specimens with great commercial potential. In this study, we examined the fructan fluctuation in these two species during their lifetime in the field (from 1 to 6 years old). First, we analyzed their morphological diversity based on vegetative characteristics. Subsequently, fructan extracts were analyzed by TLC, FT-IR, and HPAEC-PAD to identify carbohydrates. Multivariate analyses of the morphological parameters indicated a morphological divergence between the two species. Furthermore, we found that the concentration of simple carbohydrates and fructans, as well as the fructan DP, changed during plant development. Glucose, fructose, and fructooligosaccharides (FOS) were more abundant in A. potatorum, while A. angustifolia showed a greater amount of sucrose and fructans with a high DP. Fructan DP heatmaps were constructed using HPAEC-PAD profiles—the heatmaps were very helpful for establishing an easy correlation between age and the carbohydrate types present in the fructan extracts. This study is an important contribution to the agave fructan knowledge of the Mexican agave diversity.

Morphological and genetic diversity of traditional varieties of agave in Hidalgo State, Mexico

The agaves are plants of cultural importance which have been used by humans for about 10,000 years and about 40 specific uses. The most culturally and economically important of those uses are for the production of fermented (pulque) and distilled beverages (mescal). Pulque continues to be produced in nearly all of Mexico, and the agaves used for this purpose have shown domestication syndrome. We carry out an ethnobotanical, morphological, and genetic analysis of the traditional varieties of pulque agave used in the production of aguamiel (agave sap) and pulque in the state of Hidalgo. We did semi-structured interviews, free listings, and tours with 11 agave managers. We analyzed morphology and studied genetic diversity and structure using nuclear microsatellites. We found wild-collected, tolerated, transplanted, and cultivated varieties of agave. This comprised 19 traditional varieties of pulque agave, 12 of them in production during the study, which corresponded to the species Agave americana, A. salmiana y A. mapisaga and five intraspecific entities. The varieties were grouped morphologically according to a management gradient; the wild-collected varieties were the smallest, with more lateral teeth and a larger terminal spine. The cultivated varieties clearly exhibited domestication syndrome, with larger plants and smaller dentition. The expected heterozygosity (He) of the varieties ranged from 0.204 to 0.721. Bayesian clustering suggested the existence of three genetic groups, both at the level of traditional varieties of pulque agaves and for management categories, a result that matches multivariate clustering. Pulque producers in the studied localities maintain high agrobiodiversity. The cultivated varieties exhibit domestication syndrome, as has been reported for other species of the genus with the same selection purposes. Our results support the hypothesis of a decrease in genetic diversity in crops compared to wild-growing agaves, which seems to be due to vegetative propagation, among other factors.

Use, perception, and local management of Copernicia prunifera (Miller) H. E. Moore in rural communities in the Brazilian Savanna

BACKGROUND

Copernicia prunifera belongs to the Arecaceae family, and its production chain includes a set of economic activities based on the use of the stipe, petiole, fiber, fruits, roots, and leaves from which carnaúba wax is extracted, an economically valuable resource in the region. This study aimed to evaluate the uses, management, and perception of the species by local extractors.

METHODS

Two communities were studied, Bem Quer, where 15 extractors of carnaúba leaves were interviewed, and Cana, where 21 extractors considered specialists were interviewed, totaling a sample of 36 interviewees. Interviewees were asked questions about uses, ways of handling, and perception of morphological variation in the carnaúba leaves. The number of leaves extracted and the income obtained from the sale of leaves were estimated from interviews and notes that each leader of extractors held during the year of the research and previous years, as well as direct observations made by researchers in the communities which recollection area of straw hold about 80 thousand individuals of C. prunifera. A regression analysis was used to explore the relationships between social variables (age, time in extractive activity, and income obtained from extraction) with the number of leaves exploited.

RESULTS

The leaf was indicated as the most used part, from which an important powder is extracted for the production of wax. In addition, the leaf was also indicated to be used for fertilization and construction. The relationship between the socioeconomic variables, income from extraction, and the number of leaves extracted (in thousands) was significant (R² = 0.73 and p < 0.001). However, the other variables analyzed in this study, such as the time spent extracting leaves and the years of residence in the community (R² = 0.03 and p > 0.05); the number of leaves extracted and interviewee age (R²= 0.05 and p > 0.05); and the number of leaves extracted and extraction time (R² = 0.04 and p > 0.05) did not indicate a relationship.

CONCLUSION

Local extractors observed that new leaves have the highest sales value, as they have the highest production of powder. In addition, economic factor is the preponderant force that directs the management strategies of native species. For this species, however, morphological and genetic studies are needed for further clarification.

Can medicinal use protect plant species from wood uses? Evidence from Northeastern Brazil

Several ethnobotanical studies have attempted to understand the criteria for the differential use of plant resources. However, we need more effort to understand the interaction between local uses: how using a species for a given purpose may affect its use for another purpose. Thus, we hypothesize that high importance species in a more specialized category of use may have their use reduced for other categories with a more generalist nature. We have conducted the study in three rural communities in northeastern Brazil, set in seasonally dry tropical forest areas. We applied the free-list technique to identify woody species used for medicinal and/or wood purposes (fuelwood, construction and technology). Respondents rated the species according to their efficiency for wood purposes and their local availability. We performed a multiple regression to assess the effects of medicinal popularity, perceived availability, and perceived efficiency for wood uses over the species popularity for wood uses. Our results showed that medicinal use has a significant protective effect against wood uses. Perceived availability and efficiency were significant explanatory variables for wood use. Maintaining the medicinal importance of certain species can be a powerful tool in protecting their populations against more harmful uses.

Evolutionary ecology of Agave: distribution patterns, phylogeny, and coevolution (an homage to Howard S. Gentry)

With more than 200 species, the genus Agave is one of the most interesting and complex groups of plants in the world, considering for instance its great diversity and adaptations. The adaptations include the production of a single, massive inflorescence (the largest among plants) where after growing for many years, sometimes more than 30, the rosette dies shortly afterward, and the remarkable coevolution with their main pollinators, nectarivorous bats, in particular of the genus Leptonycteris. The physiological adaptations of Agave species include a photosynthetic metabolism that allows efficient use of water and a large degree of succulence, helping to store water and resources for their massive flowering event. Ecologically, the agaves are keystone species on which numerous animal species depend for their subsistence due to the large amounts of pollen and nectar they produce, that support many pollinators, including bats, perching birds, hummingbirds, moths, and bees. Moreover, in many regions of Mexico and in the southwestern United States, agaves are dominant species. We describe the contributions of H. S. Gentry to the understanding of agaves and review recent advances on the study of the ecology and evolution of the genus. We analyze the present and inferred past distribution patterns of different species in the genus, describing differences in their climatic niche and adaptations to dry conditions. We interpret these patterns using molecular clock data and phylogenetic analyses and information of their coevolving pollinators and from phylogeographic, morphological, and ecological studies and discuss the prospects for their future conservation and management.

Morphological Diversity and Genetic Relationships in Pulque Production Agaves in Tlaxcala, Mexico, by Means of Unsupervised Learning and Gene Sequencing Analysis

Pulque is one of the oldest fermented beverages, with its origins dating back to pre-Hispanic Mexico. Recently, public consumption has increased. However, the majority of Agave plantations for pulque production have disappeared or been abandoned in recent decades. To create strategies for the conservation and production of pulque agaves, it is necessary to first determine their taxonomic identities and to better understand their genetic and morphological diversity. Despite the historical importance of pulque in Mexico, little attention has been placed on the study of Agave plants used for its production. Therefore, we analyzed the morphological diversity of vegetative characters of nine landraces of two Agave species (A. salmiana and A. mapisaga) which are widely cultivated for pulque production in Tlaxcala, Mexico. The analysis of morphological characters showed that the landraces largely clustered based on classic taxonomic relationships. One cluster of landraces associated with Agave mapisaga var. mapisaga and another with A. salmiana subsp. salmiana, but with the exception of A. salmiana subsp. salmiana "Ayoteco", which is more closely related with A. mapisaga var. mapisaga. Additionally, we analyzed the genetic relationships between 14 landraces and wild individuals using molecular markers (trnL and ITS). The identified genetic variants or haplotypes and genetic pools mainly corresponded with the species. In the case of "Ayoteco", incongruence between markers was observed. Low selection intensity, genetic flow events, and the plasticity of morphological traits may explain the high number of landraces without clear differences in their morphological diversity (vegetative characters) or genetic pools. The use of reproductive traits and massive sequencing might be useful for identifying possible morphological and genetic changes in the Agave landraces used for pulque production.

Physical, Chemical, and Microbiological Characteristics of Pulque: Management of a Fermented Beverage in Michoacán, Mexico

Pulque is a beverage that has been prepared in Mexico since pre-Hispanic times from the fermented sap of more than 30 species of wild and domesticated agaves. We conducted studies in two communities of the state of Michoacán, in central-western Mexico, where we documented its traditional preparation and analyzed the relationship between preparation conditions and the composition and dynamics of microbiological communities, as well as the physical and chemical characteristics of the beverage. In one of the communities, Santiago Undameo (SU), people boil the sap before inoculating it with pulque inoculum; this action causes this local pulque to be sweeter, less acidic, and poorer in bacteria and yeast diversity than in the other community, Tarimbaro (T), where the agave sap is not boiled and where the pulque has more diversity of microorganisms than in SU. Fermentation management, particularly boiling of the agave sap, influences the dynamics and diversity of microbial communities in the beverage.