Morphological and Molecular Genetic Characterization of Soft Date Palm (Phoenix dactylifera L.) Cultivars in Egypt

Abstract

The fruits of the date palm (Phoenix dactylifera L.) are sweet berries with a sugar content of more than 50% (El-Sharabasy, 2009). The origin of the date palm is supposed to be in Middle East (Zohary and Speigel-Roy, 1975; Zo- hary and Hopf, 1988; and Amer, 2000). In Arab countries and in the Middle East the date palm is a staple food that can be pro- duced easily under unfavorable natural and economic conditions (El-Sharabasy,2009).
During the past decades, classical methods to evaluate genetic variation have been complemented by molecular techniques. The development of so-called "DNA markers" which are based on po- lymorphisms found in proteins or DNA has greatly facilitated research in a variety of many biological branches such as tax- onomy, phylogenetic relationships and genetics (Carlson et al., 1991; Halward et al., 1992 and Abdelsalam et al., 1998).
There are a number of molecular techniques available for characterization of the variation at the DNA level, e.g. RAPD (Random Amplified Polymorphic DNA), AFLP (Amplified Fragment Length Polymorphism) and ISSR (Inter Simple Sequence Repeats). Furthermore, these techniques are able to reveal a vir- tually unlimited number of markers. For genetic diversity studies, the RAPD tech- nique shows some important advantages (Williams et al., 1990). The ISSR strategy was therefore performed to access the DNA diversity among crop genotypes (Zehdi et al., 2004). Soliman et al. (2003) used RAPD markers to study three males and four females date accessions from Egypt. Soliman et al. (2006) identify the genetic polymorphism for semi-dry date palm in Egypt using RAPD and ISSR markers.
The genetic improvement of a crop species depends on the ability to select promising plant material. To facilitate the selection process, molecular markers that are associated with important traits can be used as selection tools. The markers can
then be used to establish genetic maps, which in turn are important tools for more refined marker-assisted selection in breed- ing programs as well as for in-depth ge- netic and systematic analyses (Soliman et al., 2006). Cleary, an integrated approach is needed incorporating morphological and genetic studies to improve the know- ledge of date palm taxonomy and diversi- ty. Proteins or/and DNA attributes can be used successfully for variety identifica- tion, source of information of date palm gene bank and for studying the genetic diversity of cultivars. So, date palm can be promoted best through better characte- rization and evaluation (Soliman et al., 2006).
The objective of the present study was simplified over view framework on the identification, characterization, evalu- ation and documentation the genetic di- versity of soft date palm (Phoenix dactyli- fera L.) cultivars in Egypt. Genetic diver- sity of nine soft date palm cultivars grow- ing in Egypt was addressed to identify and describe DNA markers and morpho- logical important traits as well as molecu- lar genetic characterization relationships were examined. The achieved results have been utilized for establishing genetic markers in order to discriminate among the date palm cultivars in Egypt.