Genetic Structure of Some Iranian, New and Old Worlds Linum Usitatissimum L. Populations

In current evaluation, the genetic structure and diversity were investigated in ten linseed populations collected from five countries belong to two continents (America and Eurasia) to find different genotypes for introducing them for genetic breeding programs. We selected these populations, because they belong to different regions of Holarctic and Paleotropical phytogeographic kingdoms. For this purpose, the nuclear DNA was extracted using the CTAB-modified method and amplified using 32 ISSR primers. Genetic diversity parameters and polymorphism indexes widely varied among the evaluated populations. Moreover, the results of the analysis of variance test proved the significant genetic differences, which its great part belonged to inter-population rather than intra-population. These findings were consistent with the high G(ST) and H-T levels and small amounts of H-S and populations grouping in MDS plot, which revealed low amount of within population's diversity, except those for Arak and Masal populations. In addition, low amount of Nm, indicating a flat rate of gene flow and strong population differentiation. According to the STRUCTURE analysis and UPGMA tree of Nei's genetic distance, six genotypes were recognized among the studied populations. In the detected genotypes, populations with long geographical distances have the same genetic structure. It seems that the populations with the similar genetic structures have been originated from the same genetic diversity center. Hence, we assume that there are at least six centers of genetic diversity for flax in the world; however, evidences of ancestral gene flow were detected in genetic structure. These findings are consistent with the theory that there are several centers for flax genetic diversity around the world. Due to the high intraspecific diversity in Masal and Arak populations, individuals of these populations have great importance for genetic breeding programs of this species.