Genetic diversity has been defined as ‘any measure that quantifies the magnitude of genetic variability within a population’ (Hughes et al., 2008). The degree of genetic variation is the occurrence of different genetic variants, i.e. the number of polymorphic loci (with more than two alleles) and their frequency distributions in a given population. Genetic diversity can be evaluated at different levels: among species, breeds, between lines within a breed, and even among individuals (Toro and Caballero, 2005).