Seed viability and effect of temperature on germination of Agave angustifolia subsp. tequilana and A. mapisaga; two useful Agave species

Abstract

The aim of this study was to evaluate seed viability and germination in Agave angustifolia subsp. tequilana and A. mapisaga; two cultivated species. We hypothesized that seed viability may have been altered differentially due to different patterns of human impact and seed germination at a wide range of temperatures is related to their respective natural distribution. The biochemical tetrazolium test and germination assays in petri dishes at 15, 20, 25, 30 and 35 °C were carried out. Species and temperature factors were tested using a fixed-effects ANOVA and mean germination time (G50) and the time between 10 and 90 % (G10−90) of germination potential after 30 d were analyzed by applying a Tukey test. Based on the results from tests showing seed viability, seeds were classified as viable, unviable or lacking embryo seeds, and seed viability was considered a random effect. Agave angustifolia subsp. tequilana had a higher (p < 0.05) proportion of unviable seeds (50 %) as well as seeds which lacked embryo (28 %), whereas almost 70 % of A. mapisaga seeds were viable and only 1 % lacked embryos. Germination in A. mapisaga reached around 70 % at 15, 20, 25 and 35 °C. Germination of A. angustifolia subsp. tequilana was 28 % on average only at 25, 30 and 35 °C, at the other temperatures it was significantly lower or zero. Germination first initiated in A. mapisaga, with a statistically higher rate than in A. angustifolia subsp. tequilana. Low germination, a high proportion of unviable seeds as well as lack of embryo in A. angustifolia subsp. tequilana may be attributes intrinsic to this clone, which was selected for its precocity, high yield and distinctive blue color. Better germination in A. mapisaga at different temperatures and a high degree of seed viability may be desirable in a species selected for peasant or nonintensive traditional systems, and may indicate less humanization than that manifested by A. angustifolia subsp. tequilana.