Knowledge Bank

Date palm, Phoenix dactylifera L. (Arecaceae), is a globally important food crop. Date palms are dioecious perennials with pollen-producing and fruit-producing flowers located on separate individuals. Maximizing fruit yield requires farmers to maintain a high ratio of fruit producing (female) to pollen producing (male) plants. Flowers only appear once the plant is mature, which can take 5-8 years. The ability to quickly and accurately determine the sex of date palm seedlings would be beneficial for date palm agricultural practices. One method to determine the sex of seedlings that has shown great potential is to test for the presence of sex-specific molecular markers via Polymerase Chain Reaction (PCR). Several studies have developed date palm sex-specific PCR primers, but their efficacy has not been proven across cultivars and populations. The sex of date palm is determined by an X/Y chromosome system, with the male being heterozygous and female being homozygous for the sex determination region. In this study, primers were designed from two male-specific genes located on the Y chromosome: GPAT3 and CYP703. Previous sequencing of these genes across the genus revealed that they are present in the sex determination region of males in all 14 species of Phoenix. By designing primers that amplify male-specific DNA in the sex determining region of the Y chromosome, PCR can be used to determine the sex of date palms at the seedling stage. Seedlings from a Florida population of date palms were used in this study to test the efficacy of the molecular markers. The background of this population was unknown and potentially genetically distinct from available reference genomes. DNA extracted from leaf tissue of 5 samples, two of know sex and three of unknown sex, was used for PCR and was visualized using gel electrophoresis. The primers designed from GPAT3 and CYP703 selectively amplified DNA in the male samples. GPAT3 and CYP703 gene sequences from the male Florida samples were aligned with available GPAT3 and CYP703 reference sequences from species in the genus, Phoenix. Sequences from the Florida population shared the greatest identify with species P. sylvestris, P. paludosa, and P. canariensis. Notably not P. dactylifera. These results support that primers designed from gene sequences in P. dactylifera can accurately amplify male-specific DNA in species across the genus. The primers identified in this study will be beneficial in date palm food production systems, as it reduces the time and cost of plant sex determination from a minimum of 5 years to just one day in a laboratory.