Genetic variation within 'Medjool' and 'Deglet Noor' date (Phoenix dactylifera L.) cultivars in California detected by fluorescent-AFLP markers

Date palm (Phoenix dactylifera L.) is one of the most important fruit crops of the and climate region in countries of North Africa and Middle East and there is limited production in California. All date palms in California have always been propagated by offshoots, a vegetative propagation. Throughout the world and in California, two of the most important, widely grown date cultivars are 'Medjool' and 'Deglet Noor'. In the past, it has been difficult to identify date palm cultivars based on morphological characteristics, and even more difficult to identify genetic strains of commercial cultivars. To identify the date cultivars in California, we developed a PCR based amplified fragment length polymorphism (AFLP) analysis with near infrared fluorescence labelled primers. The AFLP markers generate large number of polymorphic bands among different date cultivars and facilitate easy identification of each cultivar. Using four AFLP primer sets (IRD700 E+TA/M+CAG, IRD800 E+AC/M+CAG, IRD700 E+TG/M+CAT, and IRD800 E+AG/ M+CAT), we evaluated the genetic variation within twenty-three 'Medjool' and thirty-three 'Deglet Noor' date accessions in California. We were able to identify large intra-varietal variation within 'Medjool' and almost none in 'Deglet Noor' using AFLP markers. These accessions of 'Medjool' date in California are representatives of the genetic constituents of 'Medjool' date from its origin. 'Medjool' dates most likely exist as a landrace variety at its location of origin, the Tafilalt region of Morocco. Another possibility is that 'Medjool' date may have a very high mutation rate. The identification of genetic variation of date cultivars using fluorescent-AFLP markers will change the direction of future germplasm collection and preservation effort of dates. The information also will be useful in future date breeding and improvement. This study demonstrated the utility of fluorescent-AFLP markers in detecting polymorphism and estimating, genetic diversity among date cultivars and accessions.