Maturation and Germination of Date Palm (Phoenix dactylifera L.) Somatic Embryos

Mouaad Amine Mazri,Reda Meziani,Boutaïna Mokhless,Ilham Belkoura,Saida Elmaataoui,Souad Nour

doi:10.15835/nsb11110403

Abstract

Maturation and germination of somatic embryos are two crucial steps in the somatic embryogenesis process. Herein, we evaluated the effects of several factors on the maturation and germination of date palm somatic embryos. Globular somatic embryos of cv. ‘Najda’ were cultured on Murashige and Skoog medium at full strength (MS), half strength (1/2MS), and one-third strength (1/3MS), with or without agar, and supplemented with various concentrations of mannitol, sorbitol, polyethylene glycol (PEG, MW 8000) and abscisic acid (ABA). Our results showed that culture medium strength and texture (liquid or semi-solid), osmotic agents, and the concentration and time of exposure to ABA influence somatic embryo maturation. The highest mean number of mature somatic embryos (106.4 per 100 mg fresh weight callus) was obtained after 3 weeks of culture on full-strength liquid MS medium supplemented with 30 g L-1 PEG and 40 µM ABA, followed by 9 weeks of culture on the same medium but without ABA. Somatic embryo germination was achieved by transferring mature embryos to MS medium containing various combinations of 1-naphthalene acetic acid (NAA), 6-benzylaminopurine (BAP) and gibberellic acid (GA3). The highest germination rate (68%) of somatic embryos occurred in the presence of 0.5 mg L-1 NAA. However, there was no significant difference with the other germination media (54-66%). Plantlet acclimatization was successfully accomplished, and the survival rate was 80% after 6 months in the glasshouse. The findings of the present study open new prospects for massive propagation of this bayoud-resistant date palm cultivar.

Highlights

Date palm (Phoenix dactylifera L.) is one of the most important fruit species in the Middle East and North Africa
When cultured in liquid state, the mean number of mature somatic embryos produced per 100 mg fresh weight (FW) callus ranged from 29.6 to 41.6, depending on medium strength (Table 1)
Our results showed that culturing embryogenic calli in an abscisic acid (ABA)-containing medium for 12 weeks hampered somatic embryo maturation (15.623.1 mature somatic embryos per 100 mg FW callus)

Summary

Introduction

Date palm (Phoenix dactylifera L.) is one of the most important fruit species in the Middle East and North Africa. In the arid and semi-arid regions of Morocco, date palm plays a major role in food providing, ecosystem preservation and agricultural economy (Sedra, 2015). This species is threatened by bayoud, a serious disease caused by the fungus Fusarium oxysporum f. The only feasible way to fight bayoud is the large-scale propagation of resistant cultivars (Ferry, 2011) Along this line, several resistant cultivars were selected by the National Institute of Agricultural Research of Morocco (INRA), including ‘Najda’, which is characterized by high fruit quality (Ferry, 2011; Sedra, 2011). Rapid and large-scale propagation of date palm can be successfully achieved through either direct organogenesis or somatic embryogenesis (Mazri and Meziani, 2015). The somatic embryogenesis process involves the induction of embryogenic calli, somatic embryo

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