Somatic embryogenesis in Euterpe edulis Martius is improved by wounding, explant orientation, and suspension culture

Illegal extraction of the heart of palm is threatening Euterpe edulis Martius with extinction. Here, we investigated the induction of somatic embryogenesis in segments of E. edulis seedlings as a means of propagating this palm species. Immature seeds were harvested from the wild and germinated in vitro. After 6 months, the seedlings were excised in the middle of the caulicle and cut either transversely into two explants, or longitudinally with the wounded surface face down, up or sideways on the medium, supplemented with picloram 150 µM. Friable calli formed from upward facing explants were transferred to a suspension culture with different concentrations of picloram (15, 25, 35, and 45 µM)and then matured in the presence of abscisic acid (1, 5, 10, and 20 µM). Explants derived from upward facing segments were placed in culture medium containing l-glutamine or hydrolyzed casein (0.0, 0.5, and 1.0 g L?1). Induction in medium with 150 µM picloram was strongest for stems with longitudinal wounds positioned upward and/or sideways; while medium with 15 µM picloram enabled strong growth of friable calli. The highest average number of proembryos (16.33)was obtained with 1.0 g L?1 hydrolyzed casein and differentiation of somatic embryos was greatest with 1 µM abscisic acid. Therefore, somatic embryogenesis of E. edulis is best achieved by placing segments from longitudinally wounded stems face up on medium containing 150 µM picloram, followed by suspension cultivation with 15 µM picloram and maturation with 1 µM abscisic acid.