Direct somatic embryogenesis from cotyledon and cotyledonary node explants in bishop's weed Trachyspermum ammi (L.) sprague

A three-stage procedure for embryogenesis in Trachyspermum ammi was developed from cotyledon and cotyledonary node explants cultured in Murashige and Skoog (MS) liquid medium supplemented with 0.2 mg 1(-1) 2,4-dichlorophenoxyacetic acid (2,4-D). Globular somatic embryos without intervening callus phase developed in 4 wk. The development of embryos to heart and torpedo stages required second-stage subculture of the explants (along with developing embryos) in liquid medium with lower concentrations of 2,4-D. Further development of embryos required a third-stage subculture in hormone-free liquid medium supplemented with 100 mg 1(-1) casein hydrolysate. Regeneration of complete plantlets occurred after the fully developed somatic embryos were transferred to solidified half-strength MS medium supplemented with 1 mg 1(-1) gibberellic acid.