Date Palm Cultivar Identification through Simple Sequence Repeats (SSRs): A Practical Approach for Next-generation Commercial Date Palm Micropropagation Production

Considerable effort is required to accurately identify specific cultivars of date palm (Phoenix dactylifera L.). Large-scale commercial facilities that practice clonal propagation of date palm require a reliable method for quality control in its production during in vitro propagation, greenhouse growth and field nursery maintenance. The recent sequencing of the date palm genome has placed increasing pressure for absolute genotyping of date palm cultivars through the development of SNP microarrays. The use of a tailored simple sequence repeat (SSR) panel, using existing microsatellites in multiplex PCR, was used in date palm cultivar identification. A population of 56 of the most important date palm cultivars in the world were evaluated with sufficient genotypic polymorphism detected to distinguish 54 of the 56. The SSR panel of existing microsatellites could not confirm 18 of the 56 cultivars. This suggests that much greater intra-varietal diversity exists within the population. This in turn correlates with the fact that selection is much less stringent on male varieties, which have fewer identifiable morphological characteristics, whereas female varieties are traditionally and strictly propagated clonally in addition to being more easily identifiable by their fruit characteristics. The remaining 38 (33 females and 5 males) were evaluated in triplicate to confirm their successful fingerprinting. Further microsatellite markers will be required to fingerprint the remaining 18. These results demonstrate that routine date palm cultivar identification of in vitro plantlets, greenhouse grown and nursery plants are possible from the point of sale and beyond.