Yeast diversity in open agave fermentations across Mexico.

Yeasts are a diverse group of fungal microorganisms that are widely used to produce fermented foods and beverages. In Mexico, open fermentations are used to obtain spirits from agave plants. Despite the prevalence of this traditional practice throughout the country, yeasts have only been isolated and studied from a limited number of distilleries. To systematically describe the diversity of yeast species from open agave fermentations, here we generate the YMX-1.0 culture collection by isolating 4524 strains from 68 sites with diverse climatic, geographical, and biological contexts. We used MALDI-TOF mass spectrometry for taxonomic classification and validated a subset of the strains by ITS and D1/D2 sequencing, which also revealed two potential novel species of Saccharomycetales. Overall, the composition of yeast communities was weakly associated with local variables and types of climate, yet a core set of six species was consistently isolated from most producing regions. To explore the intraspecific variation of the yeasts from agave fermentations, we sequenced the genomes of four isolates of the nonconventional yeast Kazachstania humilis. The genomes of these four strains were substantially distinct from a European isolate of the same species, suggesting that they may belong to different populations. Our work contributes to the understanding and conservation of an open fermentation system of great cultural and economic importance, providing a valuable resource to study the biology and genetic diversity of microorganisms living at the interface of natural and human-associated environments.

Distribution, abundance and traditional management of Agave potatorum in the Tehuacán Valley, Mexico: bases for sustainable use of non-timber forest products.

BACKGROUND: Agave species have been used for thousands of years in the Tehuacán Valley, but the current mescal production has great impact on populations of the most used species. Harvesting of A. potatorum takes place before sexual reproduction and the over-extraction put local populations at high risk. In the community of San Luis Atolotilán (SLA), mescal has been produced for one century but the growing mescal trade is leading to intensified agave extraction. Our study evaluated distribution and abundance of A. potatorum, extraction rates, management practices and economic importance for SLA households. The unbalanced relation between availability and extraction rates would be an indicator of risk requiring sustainable management strategies. Our case study aspires contributing to analyze general patterns for sustainable use for this and other forest products highly extracted. METHODS: We used bioclimatic modeling to project a map of potential distribution of the species, and ecological sampling to estimate the total availability of harvestable agaves within the territory of SLA. We used participant observation, surveys and semi-structured interviews with producers and households of SLA to document agave uses, technological and socio-economic aspects of mescal production, and to estimate extraction rates of agaves. RESULTS: Mescal production, medicine and fodder are the most important uses of A. potatorum. Its distribution area is nearly 608 ha where annually occur on average 7,296 harvestable plants, nearly 54 to 87% of them being harvested. Mescal production currently is a non-sustainable activity, requiring great changes in patterns of extraction and management adopting sustainable criteria. Local people started management planning to ensure the future availability of agaves, and the ecological information of this study has been helpful in constructing their decisions. Technical support for improving local experiences for managing populations' recovering is a priority. Interaction of scholars and local people for solving this problem is already taking place and strengthening this process may be determinant for successful results. CONCLUSIONS: Strategies for protecting particular populations, temporal substitution of agave species for mescal production, implementation of restoration and organization for fear commerce are needed for improving sustainable use of A. potatorum.

Vulnerability and risk management of Agave species in the Tehuacán Valley, México.

BACKGROUND: Our study analysed the vulnerability of the useful Agave species of the Tehuacán Valley, Mexico, considering ecological, cultural and economic aspects, and management types. We hypothesized that management intensity is proportional to the degree of risk of a species in order to decrease its vulnerability. METHODS: Distribution of Agave species was monitored in 36 types of plant associations. Ethnobotanical studies were conducted in 13 villages and six markets. The vulnerability of each species was calculated by assigning risk values to the variables analysed. The vulnerability and management intensity indexes were estimated through the scores of the first principal component of PCA. Variation of management data explained by ecological, cultural and economic information were analysed through canonical correspondence analyses (CCA). A linear regression analysis identified the relation between vulnerability and management intensity. RESULTS: We recorded presence of agave species in 20 of 36 vegetation types. Out of 34 Agave species, 28 were recorded to have one to 16 use types; 16 species are used as food, 13 for live fences, 13 for producing 'pulque', 11 for fibre and ornamental, 9 for construction. Seven species are used for preparing mescal, activity representing the highest risk. Seven Agave species are exclusively extracted from the wild and the others receive some management type. Incipient cultivation was identified in A. potatorum whose seedlings are grown in nurseries. Intensive cultivation through vegetative propagation occurs with domesticated species of wide distribution in Mexico. The highest management intensity values were recorded in widely distributed, cultivated and domesticated species, but the regionally native species more intensively managed were those with higher demand and economic value, protected by collective regulations because of their scarcity. The regression analysis indicated significant relation (R2=0.677, P<0.001) between vulnerability and management indexes. CCA explained 61.0% of variation of management intensity, mainly by socio-cultural factors (30.32%), whereas ecological data explained 7.6% and the intersection of all factors 21.36%. CONCLUSIONS: The highest vulnerability was identified in wild species restrictedly distributed and/or highly extracted. Social pressures may increase the natural vulnerability of some species and these species are particularly those native species receiving some management form.