Abstract

RODRIGUEZ-MORALES, Juana; GUILLEN, Susana  and  CASAS, Alejandro. Consequences of domestication of Stenocereus stellatus in seed size and germination in a water stress gradient. Bot. sci [online]. 2013, vol.91, n.4, pp.485-492. ISSN 2007-4476.

Stenocereus stellatus is a columnar cactus species of cultural and ecological importance in the Tehuacán Valley; their fruits are collected from wild populations but plants of this species are also silviculturally managed and cultivated in agroforestry systems. Previous studies documented morpho-physiological and genetic divergences between wild and managed populations caused by artificial selection and limitations to gene flow; nevertheless, the documented divergences could also be influenced by differences in germination and survivorship patterns of wild and cultivated seedlings in forests and managed environments. We hypothesized that artificial selection in favor of larger fruits may in turn favor larger seeds in cultivated plants that also could have higher germination rates in high humidity conditions, but more susceptible to water stress than seeds from wild plants. We evaluated fruit and seed weight and germination rates in a water stress gradient (0.0, -0.2, -0.4, -0.6, -0.8, and -1.0 Megapascals) in wild and cultivated populations. Cultivated fruits and seeds were significantly heavier (54.616 ± 1.547 g, 0.190 ± 0.017 g, respectively) than wild fruits and seeds (37.023 ± 1.122 g, 0.153 ± 0.005 g, respectively). Deviance analysis showed significant differences in starting germination (X² = 1639.0, df = 4; X² = 236.31, df = 1, respectively) and velocity (X² = 20.91, df = 4) associated to management and water potential (cultivated seeds were more susceptible to water stress than wild ones). Artificial selection favoring larger fruits has apparently influenced indirectly seed size and differences; in wild and managed environments could have influenced differences of seed susceptibility to water stress.

Keywords : columnar cacti; domestication; seed size; traditional management; water stress.

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