Sex Determination in Date Palm
The date palm (Phoenix dactylifera L.), 2n=36, is a dioecious long-lived monocotyledonous plant, with separate male and female trees. The dioecy represents the major challenge in development of breeding programs as it is impossible to distinguish tree gander till they flower approximately five to eight years after planting. Date palm is an important economic crop in Egypt where the world’s largest producer over the last two years is Egypt with 1,470,000 mt. To date, sex-differentiation mechanism is still uncertain and there is no reliable way to determine the sex of date palm plants before reproductive age across all cultivars.
Research Team : Prof. Dr. Sami S. Adawy , Dr. Mohamed Atia Omar
1- Sex-Differentiation Based on Fluorescence In Situ Hybridization (FISH) with 5S and 45S rDNA of Egyptian Date Palm Trees
This study aimed to develop a sex-specific fluorescence in situ hybridization (FISH) markers with 5S and 45S rDNA in Egyptian date palm trees (cv. Zaghloul and Siwi).The results successfully revealed clear differences between males and females belonging to both cv. Zaghloul and Siwi by using 45S rDNA FISH. The fluorescence in situ hybridization (FISH) with 45S rDNA localized two clear telomeric intermediate-signals in female trees belonging to cv. Zaghloul and Siwi. While, it exhibited three clear telomeric intermediate-signals in male trees belonging to cv. Zaghloul and Siwi. On the other hand, results of fluorescence in situ hybridization (FISH) with 5S rDNA didn’t reveal any clear differences between males and females belonging to cv. Siwi. Based on the above results, we hypothesize that the third signal (unpaired signal) of 45S rDNA probe characterized in both Siwi and Zaghloul males is located on a male chromosome (Y chromosome). This finding can be utilized and used as cytological marker to differentiate between male and female trees in Egyptian date palm at an early stage.
2- Novel Set of Sex-Specific PCR-Based Markers Reveals New Hypothesis of Sex Differentiation in Date Palm
This study employed three effective gene-targeting marker approaches (SCoT, CDDP and ITAP) in additions to AFLP, in an attempt to develop a novel set of reliable sex-specific PCR-based markers can helping in early gender determination in Egyptian date palm trees. Four SCoT, two CDDP, one ITAP and one AFLP primer/primer combination exhibited differential bands between males and females under study. These differential bands were sequenced. BLAST analysis results indicated that the eleven sequences generated from different gene-targeting marker systems (SCoT, CDDP and ITAP) revealed main similarity with master transcription factors, transcriptional activators/repressors and regulatory proteins involved in plant hormone signal transduction pathways, plant development and biosynthesis of secondary metabolites in date palm or oil palm. We speculated that kind of similarity is not just a coincidence. These results revealed hypothesis that sex differentiation is a complex but well-organized process that involves endogenous and exogenous factors regulate and control the changes in gene expression, physiology, metabolism and architecture of the plant. These results indicate that sex-differentiation process have to be addressed at system biology level for deep and better understanding.