Early Sex Determination in Date Palm (Phoenix dactylifera L.) Through Fluorescent Labeling of Sex-Specific DNA Markers

Sex determination in Phoenix dactylifera L. (Date palm) remains a critical issue for breeders due to the lack of visible sexual dimorphism in early developmental stages. This study integrates cytogenetic and molecular techniques to identify sex-linked DNA markers and their chromosomal localization in three Pakistani date palm cultivars: Medjool, Gulistan, and Dedhi in in six-month-old seedlings. Sixteen DNA markers were screened, three—SCAR, SRY, and the newly developed DP-2—effectively differentiated male and female genotypes. The SCAR marker amplified distinct bands (406 bp in females and 354 bp in males), while the SRY and DP-2 markers showed male- and female-specific sequences, respectively. Fluorescent in situ hybridization (FISH) was used to physically map these sequences on chromosomes, confirming their association with a homomorphic XY sex-determination system. The 45S rDNA marker showed differential signal patterns, supporting chromosomal differences between sexes. These results demonstrate the potential of molecular cytogenetic tools for early sex identification, offering practical benefits for commercial propagation, breeding efficiency, and conservation of date palm genetic resources.