In vitro somatic embryogenesis of Texas ebony (Ebenopsis ebano [Berland.] Barneby & J.W. Grimes)

Abstract

Texas ebony (Ebenopsis ebano [Berland.] Barneby & J.W. Grimes) is a member of the Fabaceae that is native to Mexico. Its wood has multiple uses, and its natural propagation is limited and only by seed. The present investigation describes the first report of Texas ebony somatic embryogenesis with the objective of identifying medium, growth regulator components, and culture conditions. Immature cotyledons were cultured on semisolid and in liquid media containing Murashige and Skoog (MS) basal salts plus 0.0 to 9.06 μM 2,4-dichlorophenoxyacetic acid (2,4-D). The most frequent generation of embryogenic callus occurred with cotyledons cultured in the dark in liquid medium containing 9.06 μM 2,4-D. For the maturation phase, the embryogenic calluses were subcultured on semisolid MS medium with 3.78 to 30.24 μM abscisic acid (ABA), 3% and 6% polyethylene glycol (PEG) 4000, or 3 to 5% sucrose. Sucrose at 4% and 5% induced the greatest total number of somatic embryos; however, the maturation frequency and embryo quality were both higher with 6% PEG. Histological analysis revealed the ontogeny, morphology, and development of somatic embryos. Finally, the mature somatic embryos were subcultured for germination in half-strength MS medium plus 6-benzylaminopurine (BAP; 2.22 μM and 4.44 μM), gibberellic acid (GA3; 1.45 μM and 2.89 μM), or BAP (2.22 μM) and GA3 (1.45 μM). Embryo germination was superior with 2.22 μM BAP; however, radicle generation was poor in all of the treatments. This study demonstrated that for each phase of somatic embryogenesis, specific combinations of culture medium components and incubation environment are required.