Marker-assisted sex differentiation in date palm using simple sequence repeats

Microsatellite markers containing simple sequence repeats (SSRs) are a valuable tool for genetic analysis. Our objective was to identify microsatellite markers that could be used to differentiate between male and female date palm (Phoenix dactylifera). The date palm is a dioecious plant whose sex cannot be determined until it reaches a reproductive age between 5 and 10 years. An early selection and/or differentiation of young seedlings into males and females could enhance breeding and assist research programs for genetic improvements of the date palm. Here, we report on the use of microsatellites for determining the sex of immature date palm. Using 14 microsatellite primer pairs with 129 date palm leaves and tissue culture samples from 34 cultivars which represent the major date palm diversity of Qatar, 254 microsatellite loci were detected, of these, 22 microsatellite loci could be used to identify 9 out of 12 male date palm samples (75%). The data also indicated that the heterozygous allele with the size 160/190 produced by the primer mPdCIR048 reoccurred 4 times exclusively in the 12 individual male samples but not in any of the 117 female date palm samples tested, and hence it is a promising candidate marker to detect male sex in date palm. Principal coordinate analysis (PCoA) of 12 male samples with 7 female Khasab cultivars produced 2 autonomous groups of males and females and similar results were observed with 13 female Shishi cultivars. Our results suggest that the SSR markers described here have potential in sex identification of date palm.