Polymorphism determination in two natural mezquite (Prosopis laevigata) populations using RAPD

A number of different markers (proteins, isoenzymes and RAPDs) have been used to settle taxonomic disputes and to assess genotype variability in populations of the genus Prosopis, in order to select highly productive phenotypes. In this study the genetic variability of two wild populations of Prosopis laevigata located in the Mexican states of Guanajuato (population 1) and Hidalgo (population 2), as well as that of reference specimens of P. glandulosa, P. juliflora and P. laevigata, were determined using RAPD. The dendrograms for the analysis of genetic similarity among populations and species were generated by cluster analysis using UPGMA and Jaccard’s similarity coefficient, based on 27 identified bands. The dendrograms show that the individuals from both populations of P. laevigata can be separated in two highly related groups A and B (similarity coefficient 0.938) . Five subgroups were identified in group A, and six subgroups in group B. A total of 11 different genotypes were identified, of which 6 are shared among both populations. The polymorphic profile of the reference specimen of P. laevigata (from the Botanical Garden) matched that of subgroup a, which included 47% of the individuals from population 1. The calculated similarity coefficient between P. laevigata and P. glandulosa was 0.79, whereas that of P. juliflora to the former was 0.63. Genotypic diversity was similar in both populations, differing in 5 genotypes and their relative abundance. These components of genotypic diversity are the result of a differential response to environmental conditions.