Patterns of subspecies genetic diversity among oilseed Brassica rapa as revealed by agro-morphological traits and SSR markers
Assessment of genetic diversity is an essential component in germplasm characterization and utilization. Molecular markers serve as a valuable tool to assess the genetic variation and germplasm identification, which play a key role for faba (Vicia faba L.) bean breeding. In this study, we analyzed the genetic diversity of faba bean accessions based on simple sequence repeats (SSRs) and morphological traits. Forty-six faba bean accessions, originating from different countries and from the ICARDA breeding program, were evaluated by using 15 morphological and agronomic traits and 17 simple sequence repeat (SSR) loci. Significant differences among accessions for the 15 morphological descriptors were observed. Analysis by SSR markers showed a high genetic diversity among the accessions: All SSRs showed polymorphism, and 101 alleles were revealed for all accessions. The number of alleles at each locus ranged from 2 to 10, with an average of 5.94 alleles per marker, and the polymorphic information content (PIC) values ranged from 0.38 to 0.84 with a mean of 0.69. Expected heterozygosity (He), observed heterozygosity (Ho), unbiased expected heterozygosity (UHe), and Shannon’s information index (I) showed existence of high genetic variation between accessions from different pedigree. Analyses of genetic distance of the accessions separated the accessions into two groups and seven and five subgroups according to morphological and SSR analysis, respectively. Principal component analysis (PCA) of the SSR markers showed that the first two principal components (PCs) explained a total of 43.90 % of the genetic variation and allowed to distinguish three groups of accessions. Regardless of the method of analysis, Tunisian cultivars are grouped together. For the rest of the accessions, the geographical origin did not seem to be the main factor for structuring the variability of the studied accessions. Elite accessions from the ICARDA faba bean program differed from others and clustered together. The results obtained suggested that the faba bean microsatellite markers can be used to efficiently distinguish faba bean genotypes and to estimate their genetic diversity.