Direct Organogenesis and Indirect Somatic Embryogenesis by In Vitro Reversion of Mature Female Floral Buds to a Vegetative State.

This protocol describes in vitro plant regeneration from mature female inflorescence explants of date palm (Phoenix dactylifera L.) by reversion of floral state (reproductive phase) to the vegetative state. The mature female inflorescence (fully developed) is cultured on MS induction medium containing 10 mg/L 2,4-dichlorophenoxyacetic acid (2,4-D), 3 mg/L 2-isopentenyladenine (2iP), and 2 mg/L paclobutrazol (PBZ) or 2 mg/L abscisic acid (ABA). The basal part of the petals has meristematic cells, which can be induced to initiate callus or direct shoot formation depending on the plant growth regulator amendments. Callus forms on the induction medium supplemented with PBZ after 12 weeks, whereas it differentiates into somatic embryos on a medium containing 0.1 mg/L naphthaleneacetic acid (NAA). Direct shoots are regenerated on the induction medium amended with ABA after 24 weeks. Procedures for plant regeneration from mature female inflorescence explants are described, and histological changes which occur during the reversion process are presented.

Histological Evidence of Indirect Somatic Embryogenesis from Immature Female Date Palm Inflorescences.

Rapid production of somatic embryogenesis and date palm regeneration is achieved by culturing immature female inflorescence explants. Inflorescence explants are soft, creamy in color, average 6-7 cm in length, and cultured on Murashige and Skoog (MS) medium containing 1 mg/L thidiazuron (TDZ). Callus induction occurs after 4-5 weeks of culture on the callus induction medium. Subsequently, callus develops embryogenic calli on MS medium supplemented with 0.1 mg/L naphthalene acetic acid (NAA). Histological samples were collected successively at the culturing time and during morphogenetic changes throughout the developmental stages of somatic embryos. Initiation of callus and different successive developmental stages for somatic embryos including two-celled, four-celled, globular, bipolar, and fully developed cotyledonary somatic embryos were observed. Mature somatic embryos develop within 10-12 weeks after culture establishment.