     Investigation on molecular phylogeny of some date palm (Phoenix dactylifra L.) cultivars by protein, RAPD and ISSR markers in Saudi Arabia Munshi Abdulla and Osman Gamal* Biology Department, Faculty of Applied Sciences, Umm AL-Qura University, Makka Al Mukarramah, 21955, PO Box 715 - Kingdom of Saudi Arabia *Corresponding author : geosman@uqu.edu.sa Abstract Date palm (Phoenix dactylifra L.) is one of the most important fruit crops in the Middle East. Kingdom of Saudi Arabia lies among the largest date palm fruit producer worldwide. However, little knowledge is currently available about the molecular characterization of date palm cultivars in this country. Determination of genetic variability and cultivar identification in date palm are two major importance in breeding programs, characterization of germplasm, and conservation purposes. Three types of markers such as protein, RAPD-PCR, and ISSR were applied on four important cultivars in Saudi Arabia (Med300l b1, Sugay1 b1, Khalas b1 and Sukkarib1). Intervarietal variations were investigated using five RAPD and five ISSR markers. Most of the studied markers showed intervarietal polymorphism. Protein markers were also applied to assess the genetic polymorphism. Cluster analysis by UPGMA showed two main clusters. Cultivar Sukkarib1 was located on the cluster A, with Nei and Li's coefficient equal to 0.55. Cluster B consisted of 3 other cultivars, Med300lb1, Sugayb1and Khalasb1 with 0.66-0.85 Nei and Li's similarity range. Sugay b1 and Khalas b1 were the two most closely related cultivars among the four cultivars with the highest value in the similarity for Nei and Li's coefficient 0.85. Med 300l b1 was also closely related to Sugay b1 and Khalas b1 with second highest value in the similarity matrix 0.66. The average similarity among the four cultivars was a bit more than 55%. Most of cultivars had the narrow genetic diversity as already expected. The result of the analysis can be used for the selection of possible parents to generate mapping populations. Keywords: Date palm, RAPD-PCR, protein, ISSR, SDS-PAGE, diversity, conservation Introduction The green revolution was mainly based on use of high yielding varieties. Date palm has been domesticated for at least 5000 years in the Middle East region as a most important fruit crop and represents a big source of income to oases and creates the favorable condition for improving secondary crop cultures like barely, Alfa Alfa and cloves as forage. The numbers of known date palm varieties that are distributed all over the world are approximately 5000 out of which about 450 are found only in Saudi Arabia (Bashah 1996). The average number of date palm trees in Arab countries is estimated to be about 62 million trees. In 1996 Saudi Arabia produced 570.000 tons of date worth 203 million US$ (FAO 1996). There are three main types of date based on fruit moisture, content, etc. such as soft, semidry and dry cultivars. Dates (Phoenix dactylifra L.) are dioecious perennial, monocotyledon fruit trees that belong to the family of Arecaceae and its heterogeneous genetic form makes its progeny strongly heterogeneous and variable (Fakir and Munier 1992). Multiplication of date palm is mainly done vegetatively. Therefore, individuals with economically important traits are easily cloned. Clonally propagation of elite cultivars with known high perfor- mance is highly diseried in Saudi Arabia. The main limitation for this type of propagation is the minimal production of offshoots some of which will die when separated from the mother plants. Over years many varieties have been transplanted to the areas other than original regions, and they may have been adapted and cultivated with different names. As a result, a variety may have a different name in different plantation areas or even two genetically varieties may have the same name (Torres and Tisserat 1980). This matter also reduces the genetic diversity of the cultivars, making them vulnerable to biotic and abiotic stresses. The morphological markers such as fruit characteristics have been used to describe the varieties, but these markers are significantly affected by the environment. In general, identification and evaluation of genetic diversity between cultivars based on morphological markers are very difficult and time