Date Palm Genetic Diversity Analysis Using Microsatellite Polymorphism.

Date palm (Phoenix dactylifera L.) is considered one of the great socioeconomic resources in the Middle East and the Arab regions. The tree has been and still is at the center of the comprehensive agricultural development. The number of known date palm cultivars, distributed worldwide, is approximately 3000. The success of genetic diversity conservation or any breeding program depends on an understanding of the amount and distribution of the genetic variation already in existence in the genetic pool. Development of suitable DNA molecular markers for this tree may allow researchers to estimate genetic diversity, which will ultimately lead to the genetic conservation of date palm. Simple sequence repeats (SSRs) are DNA strands, consisting of tandemly repeated mono-, di-, tri-, tetra-, or penta-nucleotide units that are arranged throughout the genomes of most eukaryotic species. Microsatellite markers, developed from genomic libraries, belong to either the transcribed region or the non-transcribed region of the genome, and there is rarely available information on their functions. Microsatellite sequences are especially suited to distinguish closely related genotypes due to a high degree of variability making them ideally suitable in population studies and the identification of closely related cultivars. This chapter focuses on the methods employed to characterize date palm genotypes using SSR markers.

NAA-Induced Direct Organogenesis from Female Immature Inflorescence Explants of Date Palm.

Micropropagation has great potential for the multiplication of female and male date palms of commercially grown cultivars by using inflorescences. This approach is simple, convenient, and much faster than the conventional method of using shoot-tip explants. We describe here a stepwise micropropagation procedure using inflorescence explants of Iraqi date palm cultivar Maktoom. Cultured explants were derived from 0.5-cm-long spike segments excised from 8 to 10-cm-long spathes. About 70% formed adventitious buds on Murashige and Skoog (MS) medium supplemented with 2 mg/L naphthalene acetic acid (NAA), 4 mg/L benzylaminopurine (BAP), and 40 g/L sucrose and maintained in the dark for 16 weeks before transferring to normal light conditions. The best multiplication rate was achieved with 3 mg/L 2ip and 2 mg/L; for shoot elongation, the best medium is MS containing 0.5 mg/L BAP, 0.5 mg/L 2ip, and 1 mg/L GA3. Well-developed shoots were cultured for rooting in half MS medium amended with 1 mg/L NAA and 45 g/L sucrose. Plantlets with well-developed roots were successfully hardened in the greenhouse. Inflorescence explants proved to be a promising alternative explant source for micropropagation of date palm cultivars.