Somatic embryogenesis from immature and mature zygotic embryos of the açaí palm (Euterpe oleracea): Induction of embryogenic cultures, morphoanatomy and its morphological characteristics

Abstract

A somatic embryogenesis protocol for the açaí palm (Euterpe oleracea Mart.) was developed, based on mature and immature zygotic embryos, to define morphoanatomically the process’s different stages and to analyze the homogeneity of nuclear DNA content by flow cytometry from calli, somatic embryos and regenerated plants. Auxin picloram (4-amino-3,5,6-trichloropicolinic acid) was tested to induce embryogenic calli at 225 and 450μM concentrations, coupled to the physiological maturing stages of zygotic embryos (mature and immature). Murashige and Skoog (MS) medium with 30gl−1 sucrose, 2.5gl−1 Phytagel, 2.5gl−1 activated charcoal and 0.5gl−1l-glutamine was employed for callus induction. Embryogenic calli with somatic embryos in initial differentiation were transferred to a culture medium with 12.3μM of 2iP and 0.6μM of NAA and 300mgl−1 of activated charcoal for differentiating and maturing somatic embryos. Plant regeneration occurred in a medium with 1.0μM BAP (N6-benzylaminopurine) and 0.5μM GA3 (gibberellic acid). The formation of embryogenic calli in all treatments was observed in the induction medium, regardless of the stage of development of the zygotic embryo. Picloram at 450μM concentration provided the best results in forming embryogenic calli (84.7%). In the differentiating and maturing stage, 100% of the explants that had an embryogenic callus formation resulted in somatic embryos. The largest rate of plant regeneration (58.7%) was noted in treatment with an induction medium of 450μM of picloram and somatic embryos obtained from immature zygotic embryos. Morphoanatomical analyses evidenced that induction of somatic embryogenesis reflected stages characteristic of the indirect kind. Regenerated plants showed normal development, with growth of roots and aerial part. Calli, somatic embryos and plants, analyzed by flow cytometry, revealed no significant differences in the estimated rates of DNA content.