Investigation of genetic variation in Tunisian date palm (Phoenix dactylifera L.) cultivars using ISSR marker systems and their relation with fruit characteristics

Phoenix dactylifera L. was introduced in Tunisia a very long time ago and plays an important socioeconomic role, especially in the south of the country. Genetic diversity and relationships among 26 cultivars were assessed with 7 ISSR primers. A total of 43 amplified bands were obtained. Principal component analyses based on Nei genetic distances showed no geographical separation with the exception of the Dhahbi cultivar, which has a limited geographical distribution. A group of cultivars that are also phonetically clustered was distinguished. These cultivars have a common maturity period and a common fruit consistency. The Mantel test emphasizes a significant correlation between genetic distance and fruit consistency (r = -0.120; P = 0.026). A significant differentiation was observed between the soft and dry subpopulations (PhiPT = 0.126; P = 0.007). Discriminant analyses highlight the association of markers with fruit consistency groups. Fruit consistency is an economically important feature. In the future, these findings may be utilized for improving management strategies in Tunisia and other countries where date palms are economically significant.