Resposta morfogênica de explantes de açaizeiro para regeneração de plantas in vitro

Abstract

Euterpe oleracea Mart., a palm species native to the Amazon region, can be propagated sexually by seeds or vegetatively, with seed propagation being the most widely used method for commercial seedling production. Because this species is open-pollinated, the clonal propagation of selected genotypes for breeding purposes is largely restricted to the production of basal shoots. Therefore, in vitro culture may provide an alternative to conventional propagation methods, particularly because it enables the large-scale production of plants under aseptic conditions within a limited space. In this context, this study aimed to evaluate the morphogenic potential of different explants of E. oleracea cultured in vitro under different concentrations of auxins and cytokinins. Four independent experiments were conducted using different explant types and plant growth regulators. In Exp. I, immature zygotic embryos were cultured on MS medium supplemented with BAP (0, 1, or 2 mg L⁻¹). In Exp. II, immature zygotic embryos were cultured on MS medium supplemented with 2,4-D (0, 5, or 10 mg L⁻¹). In Exp. III, leaf segments were cultured on MS medium supplemented with 2,4-D (0, 2.5, 5, 7.5, 10, 12.5, or 15 mg L⁻¹). In Exp. IV, shoot apices were cultured on MS medium supplemented with BAP (0; 2,5; 5; 7,5 mg L⁻¹), NAA (0; 0,1 mg L⁻¹), or combinations of both(2,5 +0,1; 5+0,1; 7,5+0,1 mg L⁻¹). All MS media were supplemented with 30 g L⁻¹ sucrose, 2 g L⁻¹ activated charcoal, and 2 g L⁻¹ Phytagel®. The experiments were arranged in a completely randomized design with ten replicates per treatment, with each tube containing one explant considered an experimental unit. The experiments were conducted for 150 days, and the data were analyzed using generalized linear models, followed by mean comparisons using Tukey’s test (p ≤ 0.05). In Exp. I, some explants showed root formation only (10% in the presence of 2 mg L⁻¹ BAP), whereas others showed shoot formation only (10% in the absence of BAP and 10% in the presence of 1 mg L⁻¹ BAP). Root and shoot formation occurred simultaneously in 30% of the explants cultured with 1 mg L⁻¹ BAP. In Exp. II, callus formation was observed in 10% of the explants in the control treatment and in 10% of those cultured with 10 mg L⁻¹ 2,4-D. In Exp. III, no callus formation was observed in immature leaf segments at any of the concentrations evaluated. In Exp. IV, neither adventitious bud nor shoot formation was observed, and the morphological response was restricted to apical elongation, which occurred in 0–40% of the explants, with no significant differences among treatments. Thus, the results indicate that, under the conditions evaluated, the different explants of E. oleracea exhibit limited potential for the induction of adventitious organogenesis and somatic embryogenesis, since the concentrations and combinations of plant growth regulators tested do not promote consistent morphogenic responses.