Molecular and morphological identification of some elite varieties of datepalms grown in Saudi Arabia

Abstract

Date palm (Phoenix dactylifera L.), is a highly out breeding, dioecious plant species of enormous geneticdiversity. Genotype identification of date palm is an intricate empirical exercise based on morphologicalcharacters. In date palms most of the female cultivars are recognised by their fruit characteristics such as size,shape, colour and taste. Morphological characters of the tree are also taken into consideration for cultivaridentification. However some date palms have similar or narrow distinguishing morphological characters thatcomplicate cultivar identification and require genetic evidence to prove phylogenetic relationships. RAPDanalysis has been successfully applied for cultivar identification of date palms. The objectives of the presentstudy were to characterize some elite cultivars of date palms using morphological characters of fruits and tocorrelate the results with RAPD markers. A total of 14 well-known cultivars of date palm (Barhy, Deglet Noor,Hilaliah, Hilwa, Khalas, Makhtomi, Moneifi, Nabtet Ali, Omal Khashab, Rothana, Sabbaka, Shagra, Sukkary,Wannanah) were selected from Saudi Arabia. Analysis of the morphological data of fruits revealed a high levelof diversity in length-width ratio, colour, shape of the fruit, fruit-base and in the percentage of area covered bythe fruit cap. The length-width ratio of these 14 cultivars ranged from 1.1 to 2.62, indicating a great variation intheir shape. Correlation of morphologic characters with genomic similarity using RAPD markers showed thatthe fruit shape is one of the characteristics most influenced by genetic variation. Wherever there wasinsignificant length-width ratio among cultivars, more genomic similarity was observed. Genetic variations atthe molecular level have resulted in the production of many elite date palm cultivars which are highly variablein fruit size, shape, colour, texture, sugar and protein content. The methodology followed in this study can beextended to other cultivars, which may ultimately result in the compilation of an authentic manual describingthe diagnostic characters of date palm cultivars with their existing synonyms. The RAPD analysis will help toresolve the ambiguity regarding the identity of narrowly-distinguishable cultivars and to assess genetic diversityfor the conservation of date palm germplasm in Saudi Arabia.