Genetic variability in Tunisian populations of faba bean (Vicia faba L. var. major) assessed by morphological and SSR markers

The genetic diversity of 21 faba bean populations was examined using morphological and molecular markers. DNA was extracted from 189 individuals and 8 microsatellite markers were genotyped individually in these 21 populations. A total of 53 alleles were obtained in all populations, with an average of 6.62 alleles per locus. The expected and observed heterozygosity was 0.38 and 0.62 respectively. The average polymorphism index content of SSR markers was 0.61, ranging from 0.31 to 0.81. The unweighted pair group method with arithmetic mean dendrogram clustered all the populations into two groups, each for them subdivided into 3 sub-groups according to geographical origin. Morphological variation showed that the populations were not grouped according to their geographical origin. Therefore, patterns of differentiation of morphological traits did not coincide with molecular differentiation, indicating that morphological variation does not reflect genetic subdivision in studied faba bean populations. Analysis of molecular variance revealed high levels of genetic variation (83%) within population and provides a good base for designing genetic improvement programs. The result of Principal Component Analysis (PCA) revealed that three dimensional principal components (PC1, PC2 and PC3) contributed 40.56% of the total variability and accounted with values of 20.64, 11.22 and 8.70%, respectively. Cluster analysis based on PCA indicated three separate groups of populations. The genetic relationships found between the 21 populations samples were the same in both the PCA and STRUCTURE analysis which support the results observed. These data may serve as a foundation for the development of faba bean breeding programs.