To explore the population structure of our sample population, Discriminant Analysis of Principal Components (DAPC) was applied to 506 individuals and 5838 SNPs. DAPC revealed three genetic clusters (Additional file 6A) using 40 principal components (PCs), maximum numbers of clusters and discovery clusters limited to 40 and 7, respectively and 6 discriminants. In addition, we employed a genomic control to assure for population structure by estimating an inflation factor λ (genomic control measures). Significant inflation was detected based on a QQ-plot of association p-values, which displayed systematic deviation from the expectation (Additional file 6B).