Histological studies on induction of somatic embryogenesis in mangabeira

Abstract

The Hancornia speciosa Gomes (Apocynaceae), is a fruit tree known as mangabeira and officially listed as a genetic resource with food potential in Brazil. The aim of this investigation was to conduct histological studies on inducing maturation of somatic embryos from explants of Hancornia speciosa Gomes. For callus induction, leaf and nodal segments of the Terra Caída accession were cultured in media with different concentrations of putrescine (0, 250, 500, 750, and 1000 µM) in MS medium with 10 mg/L of 2,4D, 5 mg/L of BAP, 1 g/L of activated carbon, and 30 g/L of sucrose, and gelled with 3 g/L of Phytagel®. At 90 days of culture in multiplication medium, the embryogenic calluses were identified and selected for the maturation phase of somatic embryos in media composed of MS salts combined with two concentrations of BAP (10 and 15 mg/L) and two concentrations of polyethylene glycol – PEG 2000 (0% and 2%) with 30 g/L of sucrose, 1 g/L of activated carbon, and 4 g/L of Phytagel®. At 90 days of culture in multiplication medium (medium II) and at 60 days of culture in maturation medium (medium IV), the callus samples were fixed in FAA. After that, the samples were infiltrated in 100% ethanol + liquid resin (1:1) for 2 hours and then in activated resin = infiltration solution for 24 hours in the refrigerator. After drying, the slides were fixed with glass varnish and then evaluated in an optical microscope (Zeiss/Jenamed2), and photomicrographs (Axiocam software) were taken of the prepared slides. The results obtained in the different histological analyses of the Terra Caída accession of Hancornia speciosa Gomes are important to show the response of the nodal and leaf segments in inducing embryogenic calluses and possible maturation of somatic embryos, providing information that collaborates in validation of future protocols of somatic embryogenesis for this species.