Regeneration of Cladrastis lutea (Fabaceae) via somatic embryogenesis

Immature embryos from 5 Cladrastis lutea (Michx.) K. Koch (yellowwood) trees were initially cultured on modified Schenk and Hildebrandt medium (SH) containing either 4.5, 9.0, 13.5 or 23 μM 2,4-D. One-third of the explants were transferred to SH medium supplemented with 25.0 μM NAA after 2 and 3 weeks respectively. The remaining explants were incubated on the initial 2,4-D containing media for 6 weeks. Groups of somatic embryos formed directly only at the proximal end of cotyledons; only a few formed as single embryos. The greatest numbers were formed from zygotic embryos explanted from 6-8 weeks post-anthesis and initially cultured on medium containing 9 or 13 μM 2,4-D. However, all treatments supported somatic embryogenesis. In the second year, explants were initially cultured on SH medium containing either 9.0, 13.5, or 23 μM 2,4-D and then transferred to SH medium containing 4.0 μM ABA after 2 or 3 weeks. ABA did not affect the development of somatic embryos. Six of 21 somatic embryos germinated on half-strength SH medium without growth regulators. Three entire plantlets were formed, but only one was established in soil.