Epicuticular wax analysis of wild and agronomically important Agave species

Abstract

Agaves are cultivated in Mexico as a source of industrial products such as fibers, nutritional supplements and alcoholic beverages. A particularly important trait present in all agaves, which makes them economically viable crops for certain geographic regions, is their ability to grow under water limiting conditions. One of the anatomical characteristics that contributes to this adaptation, is the thick layer of epicuticular waxes deposited on their surface which reduces water loss by evapotranspiration. Still, to date, and in spite of their economic importance, there has been practically no effort to improve the genetics and productivity of agaves; this investigation focuses on the differences in the content and types of the epicuticular waxes present on the surface of leaves of wild and agronomically important Agave species with different ploidy level. The agaves analyzed were two diploids [A. tequilana Weber and the hybrid H11648 (A. amaniensis Trel. & Nowell x A. angustifolia Haw. back crossed to A. amaniensis)]; two pentaploids (A. fourcroydes var. Sac ki and A. fourcroydes var. Yaax ki) and a hexaploid (A. angustifolia var. Chelem ki)The epicuticular waxes were obtained by hexane extraction and their chemical composition was established by capillary gas chromatography–mass spectrometry (GC/MS). The amount of epicuticular wax varied significantly between the different types (4.40–35.63 μg cm−2), with A. angustifolia var. Chelem Ki (hexaploid) and A. tequilana (diploid) presenting the highest and lowest amounts, respectively. With the exception of A. tequilana, n-alkanes were the main components (63.32–92.13 % of total wax) in the epicuticular wax, with hentriacontane (C31) and tritriacontane (C33) as main compounds. Alternatively, in A. tequilana two aliphatic alcohols were the main components of the wax. These results suggest a correlation between the total epicuticular wax content, the chemical composition of the wax, the ploidy level and the type of habitat in which they grow. This information contributes to the understanding of the tolerance of agaves to different types of stress.