Genetic relationships and population structure of the 407 flax accessions of the core collection. (a) Phylogenetic tree created using the Neighbor-joining (NJ) algorithm  and information from 414 neutral SSRs. Colored clusters represent the sub-groups within major groups. The scale bar indicates the Nei  minimum genetic distance. (b) Bayesian clustering (STRUCTURE K = 2). Sub-groups within groups are distributed according to the clustering obtained by the NJ analysis. Accessions with a membership coefficient Q < 0.7 were classified as admixture Group 2. (c) Average log-likelihood values (mean lnP(D) ± SD for 10 iterations) and ad-hoc statistic ΔK for K values ranging from 1 to 12.