AN EFFICIENT NOVEL PATHWAY DISCOVERED IN DATE PALM MICROPROPAGATION

Abstract

Direct somatic embryos of date palm (Phoenix dactylifera L.), '' Medjool '' spontaneously developed on the individually proliferated axillary buds. Axillary bud proliferation was occurred from shoot tips explant under dark condition after 3 recultures on modified MS (Murashige and Skoog 1962) medium supplemented with 2iP (1.0 mg/L), Kin (1.0 mg/L), BA (1.0 mg/L), NOA (0.5 mg/L) and solidified with gelrite (2.0 g/L). When buds were transferred under light condition onto the same medium contained putrescine (150 mg/L), some of them (55.56 %) showed direct embryos formation (3.78) at the surface of the buds after 8 weeks of culture incubation. When these embryos were soon removed after they became visible, they survived by transferring to a fresh medium, whereas they destroyed if left intact with the bud. Embryos cultured on the previous medium omitted BA in addition to putrescine (100 mg/L) recorded the highest significant values of multiplication rate and growth value after 6 weeks of incubation. Individual shoots cultured on basal MS medium in addition to IBA (1.0 mg/L), sucrose (30 g/L) and solidified with phytoagar (6.0 g/L) recorded the highest significant values of roots number and roots length after 8 weeks of incubation. Finally, using of mixture containing compost and perlite (1:1, v/v) recorded the highest significant percentage values of plantlets survival (80 %) and number of leaves/plantlet (3.67) as well as the highest values of leaf length (17.1 cm) after 3 months in acclimatization. Phenotypically, plantlets showed similarity in the greenhouse. INTRODUCTION Date Palm (Phoenix dactylifera L.) is dioecious perennial species (2n=36) of the Arecaceae and is one of the most important liliopsidaous fruit crop in Arab countries. The family Arecaceae comprises about 200 genera and 2500 species distributed through tropical and subtropical regions around the world (FAO statistics 2008). Date palm propagated either by seeds but the resulted seedlings differ considerably in fruit quality, harvesting time and production potential or by offshoots, but this method of propagation has been faced by the fact that date palm produce relatively few offshoots suitable for transplanting in its lifetime ( Zaid and De Wet, 2002). Rapid propagation of date palm through tissue culture is the most promising technique for production of sufficient plant materials with high quality (Sane et al., 2006). In reviewing date palm micropropagation, several reports have been published. The early attempts via zygotic embryos have been done by Schroeder (1970). However, various explants tissues have been examined i.e. shoot tip (El-Bellaj et al., 2000 and Al-Khayri, 2001), leaf primordial (Beauchesne et al., 1986; Ibrahim and Hegazy, 1998, 1999, 2001; Hegazy et al., 2009), axillary bud (Sharma et al., 1984; Zaid and Tisserat, 1983a), root (Zaid and Tisserat, 1983b) and finally inflorescence ( Drira and Benbadis, 1985; Hegazy, 2008). Organogenesis and somatic embryogenesis are the two techniques currently used in various laboratories in the world for in vitro mass propagation of date palm (Al Kaabi et al., 2007). Organogenesis in date