CONICET | Buscador de Institutos y Recursos Humanos

E. nitens is a fast-growing specie, known for resisting low temperatures. Naturally it propagates through seeds, however the late production and low viability of its seeds, in addition to its recalcitrance, hinder vegetative propagation by conventional methods, thus limiting the availability of germplasm to meet superior characteristics for the improvement of the species and the establishment of plantations that increase its competitiveness in the forest industry.The aim of this study was to evaluate the effects of the interaction of different lighting conditions in incubation, on the regeneration of adventitious buds from in vitro culture of hypocotyl and cotyledon segments. Portions of cotyledons and hypocotyls (5 mm) were used as plant material, extracted from 14 days old seedlings established in Murashige and Skoog basal medium (1962), in its original formulation with 30 g.L-1 sucrose and semi-solid (Agar Sigma A-1296, 6.5 g.L-1). Based on previous results, the explants were cultured in a medium of similar composition, with the addition of indoleacetic acid (1 µM) and 6-benzyl-aminopurine (2.21 µM). Cultures were incubated in darkness (0 µmol m-2 s-1), diffused light (58 µmol m-2 s-1, 14h photoperiod) for 6, 10 and 30 days, at a controlled temperature (27±1°C).A completely randomized experimental design was used for the experiment, with three repetitions and an experimental unit of ten cultured explants. The results were expressed as a percentage of newly formed vegetative buds per explant. The results were statistically analyzed by analysis of variance (ANOVA) and Tukey test (α=0.05) using statistical software Infostat.After 30 days of incubation the formation of adventitious buds could be observed in the two types of explants. In hypocotyls with an induction of 10 days in the dark and then direct light there was a regeneration rate of up to 40 ± 10%, whereas in cotyledons it was possible to obtain a 16.67 ± 11.55% regeneration with an induction of 6 days in the dark and then direct light. In both treatments the proliferation of multiple sprouts was evident, both from direct and indirect regeneration.The results achieved in this study allowed showing that is crucial in the formation of vegetative buds a period of darkness in the induction, depending on the type of explant and its totipotency, since the period of absence of light prevents the release of metabolites produced in oxidation processes, which generate damage and even cell death.It is important to emphasize this, because this morphogenic process opens the possibility of developing a protocol for mass propagation with a lower requirement of explant donor vitroplants.Key words: explants, regeneration, vitroplants.