Abstract

In the date palm, a dioecious mode (separatemale and female individuals) and the late initial reproductiveage (5–10 years) are major practical constraintsfor genetic improvement. Early selection on young seedlingscould enhance breeding programmes and generateexperimental male and female genetic stocks, but no cytogeneticprotocol exists for sex determination in an immaturedate palm. Here we describe a cytological methodbased on chromomycin staining which demonstratesthe occurrence of sexual chromosomes carrying distinctivenucleolar heterochromatin and thus offers, for thefirst time, the possibility of identifying male and femaleindividuals by simple analysis of root meristems. Thisobservation has been extended by in situ rDNA hybridization,confocal microscopy and dual-label flow cytometry of nuclei.