Seed production and gametophyte formation in Agave tequilana and Agave americana

Agave tequilana Weber var. azul is the raw material used in the production of tequila. This species has a life cycle of approximately 6–8 years; however, owing to the practice of removing the inflorescence to conserve accumulated sugar reserves, the main form of reproduction is asexual. Little attention has, therefore, been paid to the process of flowering and the factors leading to low levels of germination and seedling viability have not been investigated in detail. The objective of this study was to document gametophyte development, seed production, and germination in A. tequilana under different pollination treatments and in an interspecies cross with Agave americana L. Seed production and germination efficiency was low for both A. tequilana and A. americana under the different pollination treatments, although interspecies crosses did produce some viable seeds. Development of the male gametophyte in both species is of the successive type, producing pollen grains with dicolpate morphology. Female gametophyte development is of the Polygonum monosporic type. The results obtained suggest that genetic incompatibility, inbreeding effects, factors affecting pollen development and germination, or errors in female gametophyte development may contribute to the low fertility observed for A. tequilana and A. americana.