Embryogenic callus induction from in vitro culture of mature zygotic embryos of Euterpe edulis Martius (Arecaceae)
ABSTRACT Background: Euterpe edulis Martius, a symbolic species of the Atlantic Forest in Brazil, popularly known as the Juçara palm tree, does not produce axillary or basal shoots, which prevents its vegetative propagation through conventional techniques. Plant tissue culture techniques have been proposed for the clonal propagation of superior genotypes of this species. The present study aimed to evaluate the effect of 2,4-dichlorophenoxyacetic acid (2,4-D) on the induction of embryogenic calluses from mature zygotic embryos of E. edulis. Mature zygotic embryos were inoculated in culture media supplemented with different concentrations (20, 40, 80, 160, 320, 480, and 600 mg L⁻¹) of 2,4-D, while the control treatment contained no 2,4-D. The experiments were conducted in a completely randomized design. Results: After 70 days in the induction medium, three morphogenic responses were observed: seedlings, abnormal seedlings, and calluses. Increasing concentrations of 2,4-D reduced the formation of normal seedlings while enhancing callogenesis up to concentrations between 160 and 279 mg L⁻¹. At higher concentrations, embryogenic calluses or oxidized explants predominated. Morphoanatomical evaluations confirmed the embryogenic identity of the calluses, which consisted of a meristematic center surrounded by a parenchymatic zone. Neutral polysaccharides and starch grains were mainly observed in the parenchymatic zone, which was not directly involved in somatic embryo regeneration. Conclusion: This study demonstrates the formation of embryogenic calluses from in vitro cultures of zygotic embryos of Euterpe edulis. These findings contribute to the development of a complete regeneration protocol and may support the clonal propagation and conservation of this important Atlantic Forest palm species.