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Genetic diversity of Tunisian male date palm (Phoenix dactylifera L.) genotypes using morphological descriptors and molecular markers

El Kadri, Nabila, Mimoun, Mehdi Ben, Hormaza, José Ignacio
Scientia horticulturae 2019 v.253 pp. 24-34
Phoenix dactylifera, alleles, genetic distance, genetic markers, genetic variation, heterozygosity, loci, males, microsatellite repeats, pollinators, provenance, quantitative traits, seeds, Tunisia
Twenty-eight morphological characters (consisting of 15 quantitative and 13 qualitative traits) and eight SSR loci were used to study morphological and genetic diversity of 24 male date palm genotypes from Southern Tunisia. The results revealed that fourteen of the fifteen quantitative characters studied showed a high discriminating power to distinguish male date palm trees. UPGMA clustering based on morphological data classified the samples studied in five clusters. The eight SSR loci used showed polymorphism resulting in a total of 42 alleles in the samples analyzed. The number of alleles per locus varied from 3 (mPdCIR35 and mPdCIR63) to 7 (mPdCIR 25 and mPdCIR 32) with a mean of 5.4 alleles per locus. The average of observed heterozygosity (Ho), ranged between 0.13 (mPdCIR78) and 0.79 (mPdCIR25), with a mean of 0.54. The average of expected heterozygosity (He) ranged between 0.32 (mPdCIR78) and 0.74 (mPdCIR57 and mPdCIR63) with a mean of 0.61. Fis values were negative for all the markers excepted for mPdCIR015, mPdCIR035 and mPdCIR078. Fst values varied between 0.04 (mPdCIR015 and mPdCIR063) to 0.29 (mPdCIR063). The dendrogram constructed based on the data from the eight SSR primers revealed 3 clusters. No correlation (r= -0,106, p = 0.075) was obtained between distances based on quantitative morphological traits and genetic distances using the Mantel test. Results indicate a high degree of genetic diversity among date palm pollinizers in southern Tunisia, but the accessions do not group according to geographical origin due probably to the exchange of plant material and seeds among different regions of the country.