No abstract

Somatic embryogenesis is one of the most important technologies for plant regeneration of elite date palm cultivars. Recently, considerable progress has been made in the development and optimization of this technique from embryogenic cell suspension cultures. This chapter describes a procedure for the rapid development of a large number of somatic embryos from embryogenic cell suspension cultures. An efficient plant regeneration protocol via somatic embryogenesis from cell suspension cultures starting with shoot-tip explants to plantlet acclimatization also is fully described. Low concentrations of 6-benzylaminopurine (BAP) to 0.3 mg/L and high rate of subcultures each 7 days lead to improve the establishment and multiplication of somatic embryos in suspension cultures by limiting oxidative browning, associated with high total phenols and peroxidase activities. The detailed morphological observations have revealed the cells destined to become somatic embryos. Activated charcoal (AC) at 0.15 g/L has a positive effect on growth rate of somatic embryos by reducing tissue and medium browning, phenolics, and peroxidase activity.

All studies in date palm somatic embryogenesis focused on the germination of light and neglected the darkness effect on germination. Study of the effect of light and darkness incubation on germination of date palm somatic embryos led to the developing of an efficient new and simple procedure for inducing the direct date palm somatic embryos germination and conversion into plantlets. In vitro germination in darkness played a critical role in direct converting date palm somatic embryos into plantlets. Direct somatic embryos germinated in the darkness exhibit continuous growth leading to forming etiolation longitudinal stems and thin leaves, while somatic embryos germinated in the light show inhibition of longitudinal growth with the formation of short stems and green wide leaves. Darkness germination process had decreased significantly the conversion period of direct somatic embryos into plantlets to less than 12 weeks. Darkness incubation led to germination and elongation in one stage, while the incubation in the light required two stages the embryo germination stage then the elongation stage. Somatic embryos grown in darkness had more protein and less phenolic compounds than embryos grown in the light. These results had led to significantly decrease in the protocol period and modified the protocol stages of date palm somatic embryos germination and conversion into plantlets, ending with better germination and reduction of time and costs.