EMBRYOGENIC CALLUS INDUCTION FROM in vitro CULTURE OF MATURE ZYGOTIC EMBRYOS OF Euterpe edulis Martius (ARECACEAE)

Abstract

Euterpe edulis Martius, a symbolic species of the Atlantic Forest in Brazil, does not produce axillary or basal shoots, which prevents vegetative propagation through conventional techniques. 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 640 mg L^-1) of 2,4-D. In the control treatment, no 2,4-D was added. The experiments were carried out in a completely randomized design. After 70 days in induction medium, three morphogenic responses were observed: seedlings, abnormal seedlings, and calluses. Increasing concentrations of 2,4-D reduced normal seedling formation while enhancing callogenesis up to an optimal level (279 mg L⁻¹). At higher concentrations, embryogenic calluses or oxidized explants predominated, with a high percentage of non-responsive tissues. Morphoanatomical evaluations revealed the embryogenic potential of the calluses. These structures 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. In summary, we report here the formation of embryogenic calluses from the in vitro culture of zygotic embryos of E. edulis. We believe that these data may be helpful to the establishment of a complete regeneration protocol for this critical plant palm species.