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Genetic diversity and demographic evolution of baobab (Adansonia digitata L., Bombacoideae, Malvaceae) populations in Senegalese Sahelian areas

African Journal of Biotechnology. Vol. 12(38), pp. 5627-5639, 18 September, 2013.
Amadou Lamine NDOYE1, Toffène DIOME2,3, Mame Codou GUEYE4, Mbacké SEMBENE2,3 and
Mame Ourèye SY1*

SummaryThis study evaluated the spatial genetic structure of baobab (Adansonia digitata L.) populations from
three agroecological sites located in sahelian zone of Senegal using ITS1, 5.8S rDNA and ITS2 gene
sequences. To determine the extent of isolation, gene sequences were analyzed between and among
three sahelian baobab populations. At least 25 haplotypes of baobab (A. digitata L.) were revealed in
Senegal (6, 9 and 10, respectively in Dakar, Bandia and Widou Thiengoly). Private haplotypes found in
each locality show that there is an adaptation of the plant to environmental conditions prevailing in
each site. Indeed, nucleotide diversity was more important in Dakar (0.00527) ; it ranges from 0.00483 to
0.00060 for Bandia and Widou populations, respectively. Curves of mismatch distribution show that the
population of Ferlo has undergone a recent demographic expansion. Although Bandia and Dakar
populations were polyphyletic ; each shows a balanced expansion. Fst values ranging from 0.62946 to
0.90712 correlates a strong genetic differentiation between sites. A correlation between geographic and
genetic distances was not highlighted by the Mantel’s test but phylogenetic trees of maximum
likelihood and Bayesian inference have assigned two clades demonstrating that population of Ferlo
(Widou) form a different ecotype from those of Bandia and Dakar.

Key words : ITS1, 5.8S, ITS2, Adansonia digitata, haplotype, genetic diversity, demographic evolution.