Variability and genetic structure in a commercial field of tequila plants, Agave tequilana Weber (Agavaceae)

Crops of the tequila plant (Agave tequilana)are produced mainly from offshoots of mother plants in established commercial fields. This propagation method is significant, as it is believed that it facilitates the spread of disease because of the crop's low genetic variability and is also necessary because it is regulate the use of just that variety in tequila industry. Different levels of genetic variability have been reported for A. tequilana and so we tested individuals from representative cultivation zones to determine the actual variability in fields and to assess the genetic structure of populations in commercial plantations. Four additional Agave spp. were used as a control group while Fourcrea spp. individuals were used as an external group. Morphological traits and molecular markers were analyzed. The differences between A. tequilana individuals collected from southern Jalisco state and those collected in the principal Denomination of Origin zone confirmed the existence of different genotypes, which were conserved in different regions by asexual propagation. Leaf length, plant height and number of leaves were the most significant variables that explained the variability within the A. tequilana group. At the molecular level, we found genetic differentiation with a minimum similarity of 0.253 (Jaccard's coefficient)and genetic structure analysis indicated five groups with significant genotypic differences. Genetic structure analysis, grouped accessions according to the dispersion of plant material from the initial sites of cultivation. These results might facilitate the correlation of different groups with crop yield or tequila quality and the establishment of elite lines for breeding programs. It is recommendable in a future, to determinate the different levels of inulines produced by each detected group.