Salwa Zehdi

Male‐specific DNA markers provide genetic evidence of an XY chromosome system, a recombination arrest and allow the tracing of paternal lineages in date palm

Whether sex chromosomes are differentiated is an important aspect of our knowledge of dioecious plants, such as date palm (Phoenix dactylifera). In this crop plant, the female individuals produce dates, and are thus the more valuable sex. However, there is no way to identify the sex of date palm plants before reproductive age, and the sex-determining mechanism is still unclear. To identify sex-linked microsatellite markers, we surveyed a set of 52 male and 55 female genotypes representing the geographical diversity of the species. We found three genetically linked loci that are heterozygous only in males. Male-specific alleles allowed us to identify the gender in 100% of individuals. These results confirm the existence of an XY chromosomal system with a nonrecombining XY-like region in the date palm genome. The distribution of Y haplotypes in western and eastern haplogroups allowed us to trace two male ancestral paternal lineages that account for all known Y diversity in date palm. The very low diversity associated with Y haplotypes is consistent with clonal paternal transmission of a nonrecombining male-determining region. Our results establish the date palm as a biological model with one of the most ancient sex chromosomes in flowering plants.

Molecular characterization of Mauritanian date palm cultivars using plasmid-like DNAs markers

Mauritanian date palm cultivars and progenies of two controlled crosses were analyzed according to the identity of mitochondrial plasmid-like DNAs. Starting from total genomic DNA and appropriate primers, polymerase chain reaction was designed to amplify either a 373-bp or a 265-bp fragments corresponding to the S and the R-plasmid respectively. Data proved that 5 cultivars out of 10 studied have exhibited the R-plasmid suggesting their resistance to the fusariosis. The existence of intra-cultivar variability has also been revealed in the cv. Ahmar. In addition, analysis throughout progenies of two controlled crosses suggested the strict maternal transmission of the date palms’ mitochondrial genome.