Genetic Structure of Edible Tiger Nut Accessions (Cyperus esculentus L, 1753) in Côte d’Ivoire: Implication in Improvment and Conservation Strategy

Abstract

Cyperus esculentus represents an important source of income for the vulnerable Ivorian population, particularly women. Its low productivity in agroecosystems justifies the implementation of a genetic improvement program, requiring knowledge of the genetic diversity of locally cultivated accessions. Thus, this study evaluated the molecular diversity of 39 accessions of African edible tiger nut collected from eight localities in Côte d'Ivoire using SSR molecular markers. To achieve this Franco-objective, DNA from young leaves of these accessions was extracted using the CTAB method and amplified using five microsatellite markers. From the electrophoregrams and with the help of four software programs (GenAlEx 6.5, MEGA 12.0.9, adegenet (R 3.5.1), and STRUCTURE 2.3.4), the parameters of intra- and inter-population genetic diversity (Na, Ne, Ho, He, I, P, FIS, FIT, FST, Nm), genetic structure (AMOVA), and spatial structuring (Neighbor-Joining dendrogram, PCoA, DAPC, STRUCTURE) were determined. The result of the statistical analyzes indicates a very high polymorphism (P=0.975%) of the loci and an average allelic richness of three alleles confirmed by the number of effective alleles (Ne = 2.269) and the Shannon index (I = 0.871). The studied populations show an observed heterozygosity value of (Ho=0.100) against an expected heterozygosity of (He=0.516) and an inbreeding rate of (FIS = 0.787). Also, the analysis of the genetic structure indicates that 74% of the genetic variability is found within the populations, compared to 12% between the populations. Moreover, the spatial structuring revealed three main genetic groups. These results suggest a marked genetic structuring, modulated by human exchanges of material and clonal reproduction. Additional controls  are recommended to exclude potential genotyping biases before concluding on inbreeding. These data nevertheless provide a useful basis for the conservation and improvement of tiger nuts in  Côte d'Ivoire.