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In vitro comparative study of adaptive strategies in Hylocereus species, Cactaceae, with contrasted ecological distribution

Abstract:

Hylocereus ocamponis and Hylocereus triangularis are two phylogenetically closely-related cacti species that show completely different growth habits. The first species occurs in dry ecosystems while the second one growths in the tropical rainforest, in dry forest western and the amazonic region Ecuadorian. In this work, in vitro culture was used as platform to study adaptations in both species. In vitro culture offers the possibility to compare responses to growth regulators under highly controlled conditions. Combinations of growth regulators (TDZ, BAP, NAA, 2,4-D and KIN) were evaluated in different types of explants to study their morphogenetic responses and make a connection with stress tolerance and adaptive capacity (phenotypic plasticity) in H. ocamponis and H. triangularis. H. triangularis showed a greater dynamic range of responses to the assayed treatments, especially during callus and cladode formation. Treatments produced in most cases an inhibition in H. ocamponis explants compared to the untreated control except during root induction, which can be directly related to its growing habits. In vitro culture proved to be a useful methodology to study adaptations in species with contrasting ecological distributions and revealed a great plasticity in H. triangularis that is consistent with its capacity to conquer new habitats.