Date palm (Phoenix dactylifera L.) is an important fruit crop in many arid areas and understanding the relatedness among genotypes is important for effective date palm improvement. Inter-primer binding site (iPBS) markers were used to assess the molecular variation and genetic diversity of 54 and 12 date palm (Phoenix dactylifera L.) genotypes collected from Australia and Iraq, respectively. The main objectives were to survey genetic diversity and to determine varietal differences among the collected date palm germplasm. The PCR of five iPBS primers (dominant markers) selected from an initial 60 produced a total of 111 bands ranging from 180 to 3500 bp. The PIC value for these five primers ranged from 0.2135 to 0.3289 with a mean value 0.2816. The mean expected heterozygosity (0.218), mean unbiased expected heterozygosity (0.229) and Shannon's information index (0.33) indicated a high level of inbreeding among the accessions tested. Ordination and cluster analysis showed that the genetic relationships among all accessions could be separated into geographic origin; specifically Iraqi female cultivars, exotic female cultivars collected in Australia and male accessions also collected in Australia, with a few exceptions. Date palm accessions collected in Australia and Iraq are highly divergent and the abundant genetic diversity observed provides a beginning platform for date palm improvement in Australia. The iPBS PCR-based genome fingerprinting technology used in this study is low-cost and effectively differentiated accessions of date palm and their related species.

Understanding genetic relatedness in date palm (Phoenix dactylifera L.) germplasm is important for effective plant improvement. Microsatellite (SSR) markers were used to assess the molecular variation and population structure of 60 Australian locally selected and exotic genotypes (24 female, 30 male and 6 related species), 12 Iraqi female cultivars and 10 female cultivars from Jordan. The main objectives were to survey genetic diversity and determine population structure in this core date palm collection which includes the most important and widely distributed cultivars in Australia. These Australian accessions were then compared to those originating from the date palm center of origin in the Middle East. PCR of 17 SSR primers (co-dominant markers) produced a total of 313 alleles ranging from 5 to 31 with an average of 18.4 alleles per locus. The PIC value for these 17 primers ranged from 0.4771 to 0.8199 with a mean of 0.670. The mean expected heterozygosity (0.841), mean observed heterozygosity (0.946) and Shannon's information index (2.067) indicated a high level of genetic diversity among the accessions. Multi-locus DNA fingerprints based on the 17 SSR loci unambiguously differentiated all accessions and revealed an absence of duplicated samples. Ordination and cluster analyses showed that the Australian accessions did not group together geographically; instead separate male and female groups differentiated among the six clusters. A Bayesian cluster analysis also partitioned the accessions into six groups and this result was largely compatible with the result of ordination analysis. The Australian date palm germplasm is highly diverse and thus provides an effective platform for plant improvement, enhancement of date production and the conservation of genetic resources.

Rapid and efficient propagation methods that avoid the use of mutagenic growth regulators are required for date palm breeding and cultivation. The effects of different growth regulators on micropropagation of six female cultivars of date palm including Barhee, Medjool, Khalas, Khadrawi, Nemeishi and River Gem and the male cultivar Jarvis were invstigated. The experiments were conducted in vitro using floral explants of female and male mature inflorescences. Embryogenic callus induction and proliferation were significantly higher (93%) in the woody plant nutrient culture medium (WPM) supplemented with 5mg l-1 Thidiazuron (TDZ). The addition of zeatin to the medium was most effective for shoot regeneration from callus and this enhanced regeneration frequency and the average number of shoots obtained per explant. The highest number of shoots/explant (16) was obtained using 2 mg l-1 zeatin in WPM and WPM with 0.5 mg l-1 GA 3 and 2 mg l-1 zeatin enhanced shoot length significantly. Bud initiation and adventitious shoot formation 16 weeks after flower culture was enhanced by WPM supplemented with 1.5 mg l-1 2,4-D and 5 mg l-1 2ip. Sub-culturing of formed buds on a multiplication medium supplemented with 3.0 mg l-1 zeatin and 0.3 mg l-1 NAA produced the highest average number of buds. Adventitious shoot elongation (up to 7.64 cm) was maximized using a WPM medium with 0.5 mg l-1 GA 3 and 3 mg l-1 zeatin. Optimum rooting (81%) was achieved when shoots were transferred to a medium with 0.2 mg l-1 NAA. The survival rate was 80% and the plants were subsequently transferred to bigger pots and acclimatized for field planting. No phenotypic differences were observed among the regenerants. This observation was validated using a set of five highly polymorphic iPBS and SSR markers.

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