Analysis of Tunisian date palm germplasm using simple sequence repeat primers

Inter Simple Sequence Repeat (ISSR) markers involve polymerase chain reaction (PCR) amplification of DNA using a single primer composed of a microsatellite sequence. ISSR technology rapidly reveals high polymorphic fingerprints and determines genetic diversity. We used genetic markers generated from selected ISSR primers to assess genetic diversity among a set of Tunisian date palm varieties. Seven primers were used to cluster 12 date palm varieties and 77 polymorphic markers were sufficient to identify all of the varieties. These discrete molecular markers were used to estimate genetic distances among the 12 accessions and to examine their genetic relationships. Data analysis identified phenetic groups that were in agreement with those obtained according to agronomic traits and random amplified polymorphic DNA (RAPD) markers. Among the 12 simple sequence repeat (SSR) motifs tested, the most abundant were AG. Key Words: Genetic diversity; ISSR polymorphisms; date palm; Pheonix dactylifera. African Journal of Biotechnology Vol. 3 (4), 2004: 215-21

Analysis of Tunisian date palm germplasm using simple sequence repeat primers

Inter Simple Sequence Repeat (ISSR) markers involve polymerase chain reaction (PCR) amplification of DNA using a single primer composed of a microsatellite sequence. ISSR technology rapidly reveals high polymorphic fingerprints and determines genetic diversity. We used genetic markers generated from selected ISSR primers to assess genetic diversity among a set of Tunisian date palm varieties. Seven primers were used to cluster 12 date palm varieties and 77 polymorphic markers were sufficient to identify all of the varieties. These discrete molecular markers were used to estimate genetic distances among the 12 accessions and to examine their genetic relationships. Data analysis identified phenetic groups that were in agreement with those obtained according to agronomic traits and random amplified polymorphic DNA (RAPD) markers. Among the 12 simple sequence repeat (SSR) motifs tested, the most abundant were AG

Integration of ethnobotany and population genetics uncovers the agrobiodiversity of date palms of Siwa Oasis (Egypt) and their importance to the evolutionary history of the species

Crop diversity is shaped by biological and social processes interacting at different spatiotemporal scales. Here we combined population genetics and ethnobotany to investigate date palm (Phoenix dactylifera L.) diversity in Siwa Oasis, Egypt. Based on interviews with farmers and observation of practices in the field, we collected 149 date palms from Siwa Oasis and 27 uncultivated date palms from abandoned oases in the surrounding desert. Using genotyping data from 18 nuclear and plastid microsatellite loci, we confirmed that some named types each constitute a clonal line, i.e. a true-to-type cultivar. We also found that others are collections of clonal lines, i.e. ethnovarieties, or even unrelated samples, i.e. local categories. This alters current assessments of agrobiodiversity, which are visibly underestimated, and uncovers the impact of low-intensity, but highly effective, farming practices on biodiversity. These hardly observable practices, hypothesized by ethnographic survey and confirmed by genetic analysis, are enabled by the way Isiwans conceive and classify living beings in their oasis, which do not quite match the way biologists do: a classic disparity of etic vs. emic categorizations. In addition, we established that Siwa date palms represent a unique and highly diverse genetic cluster, rather than a subset of North African and Middle Eastern palm diversity. As previously shown, North African date palms display evidence of introgression by the wild relative Phoenix theophrasti, and we found that the uncultivated date palms from the abandoned oases share even more alleles with this species than cultivated palms in this region. The study of Siwa date palms could hence be a key to the understanding of date palm diversification in North Africa. Integration of ethnography and population genetics promoted the understanding of the interplay between diversity management in the oasis (short-time scale), and the origins and dynamic of diversity through domestication and diversification (long-time scale)

Evolution of sex chromosomes prior to speciation in the dioecious Phoenix species

International audienceUnderstanding the driving forces and molecular processes underlying dioecy and sex chromosome evolution, leading from hermaphroditism to the occurrence of male and female individuals, is of considerable interest in fundamental and applied research. The genus Phoenix, belonging to the Arecaceae family, consists uniquely of dioecious species. Phylogenetic data suggest that the genus Phoenix has diverged from a hermaphroditic ancestor which is also shared with its closest relatives. We have investigated the cessation of recombination in the sex-determination region within the genus Phoenix as a whole by extending the analysis of P. dactylifera SSR sex-related loci to eight other species within the genus. Phylogenetic analysis of a date palm sex-linked PdMYB1 gene in these species has revealed that sex-linked alleles have not clustered in a species-dependent way but rather in X and Y-allele clusters. Our data show that sex chromosomes evolved from a common autosomal origin before the diversification of the extant dioecious species

Endemic insular and coastal Tunisian date palm genetic diversity

The breeding of crop species relies on the valorisation of ancestral or wild varieties to enrich the cultivated germplasm. The Tunisian date palm genetic patrimony is being threatened by diversity loss and global climate change. We have conducted a genetic study to evaluate the potential of spontaneous coastal resources to improve the currently exploited Tunisian date palm genetic pool. Eighteen microsatellite loci of Phoenix dactylifera L. were used to compare the genetic diversity of coastal accessions from Kerkennah, Djerba, GabSs and continental date palm accessions from Tozeur. A collection of 105 date palms from the four regions was analysed. This study has provided us with an extensive understanding of the local genetic diversity and its distribution. The coastal date palm genotypes exhibit a high and specific genetic diversity. These genotypes are certainly an untapped reservoir of agronomically important genes to improve cultivated germplasm in continental date palm