Optimization of somatic embryogenesis inEuterpe edulisMartius using auxin analogs and atomic force microscopy

Euterpe edulis Martius is an endangered species of the Atlantic Forest, whose fruits have high antioxidant potential, and propagated exclusively by seeds. The present study assessed the ability of different auxin inducers and picloram analogs to trigger somatic embryogenesis in E. edulis . Immature seeds were harvested, and their zygotic embryos were excised and grown in MS culture medium supplemented with 2,4-D dichlorophenoxyacetic acid (2,4-D) or picloram at 150, 300, 450, 600 µM. The activity of picloram analogs triclopyr and clopyralid was evaluated in semisolid MS medium. At maturation and germination, picloram-derived calli and somatic embryos isolated from triclopyr-grown cultures were first transferred to pre-maturation medium and, after 30 days, to basal MS or MS medium supplemented with either 5 µM abscisic acid or 0.53 µM 1-naphthaleneacetic acid plus 12.3 µM 2-isopentenyladenine. Finally, somatic embryos with root protrusions were transferred to MS medium devoid of sucrose for 30 days and then acclimatized ex vitro. Scanning, transmission, and atomic force microscopy revealed that picloram was superior to 2,4-D but less effective than triclopyr (100 µM) in inducing embryogenesis. Maturation and germination of somatic embryos in E. edulis can be maximized by 5 µM abscisic acid, and selecting calli via atomic force microscopy. Highlight This work opens novel roads for embryogenic induction, using a new and more efficient inducer than the usual ones, and an innovative evaluation technique based on AFM.