Genetic stability among date palm plantlets regenerated from petiole explants
The regeneration capacity between the shoot tip and petiole explants that excised from two date palm (Phoenix dactylifera L.) cutivar namely Unknown and Ferhi was compared. It was noted that the shoot tip explants started to swill after several subculture when placed on Murashige and Skoog (MS) medium supplemented with 100 mg l-1 2, 4-D, 3 mg l-1 6-Benzyladenine (BA) and 3 g l-1 activated charcoal while embryogenic calli was induced by culturing the petiole explants on MS medium supplemented with 1 mgl-1 2, 4-D. The data indicate that callus induction efficiency decreased with increasing 2, 4-D in the culture media. The embryonic calli were transferred into shoot inducing medium containing 1 mgl-1 BA and 1 mgl-1 naphthaleneacetic acid (NAA). The developed protocol for plant regeneration using petiole explant is repeatable and takes less time (four months) compared with the shoot tips as explants which take much time (3 years). Genetic similarity between the mother plants of the Unknown and Ferhi cultivars and several plants regenerated in vitro from both cultivars were examined by random amplification polymorphic DNA (RAPD) analysis using 10 random primers. Each primer generated a unique set of amplification products ranging in size from 200-2600 bp. The data indicate that the regenerated plants from the Unknown and Ferhi cultivars showed 36.2 and 37.8 % polymorphism and sharing 63.8 and 62.2% of similarities, respectively with their mother plants. The level of genetic similarity between regenerated plants and their mother plants as revealed by RAPD analysis indicate that this regeneration protocol is promising and can be used to produce transgenic date palm plants expressing economically important genes.
Key words: Date palm, somatic embryogenesis, genetic stability, RAPD anaysis.