Analysis of genetic diversity and population structure in drought tolerant flax (Linum usitatissimum) cultivars based on SSR-markers

Flax (Linum usitatissimum L.) is an annual herb that can be divided into oilseed flax and fibre flax during evolution. In order to clarify the genetic relationship of typical drought tolerant flax cultivars we systematically studied the genetic diversity of 29 drought-resistant flax cultivars by SSR molecular markers. The results showed that 30 pairs of SSR primers amplified 330 bands from 29 drought-resistant flax cultivars, of which 307 bands were polymorphic, with a polymorphism ratio of 93.01%. Each pair of primers had an average of 10.2 polymorphic loci, and the average polymorphism information content (PIC) of primers was 0.9254. The effective alleles (Ne) ranged from 1.2622 to 1.6399, the Nei's index (H) ranged from 0.1833 to 0.3777, and Shannon's index (I) ranged from 0.3146 to 0.5612. UPGMA clustering analysis showed that 29 drought-resistant flax cultivars were divided into A and B categories at the genetic similarity coefficient of 0.41. The results of population structure analysis show that when K=2, 29 drought-resistant flax cultivars can be divided into 2 subgroups. The results of principal coordinate analysis showed that the two populations are relatively far apart on axis PCoA1 and can be significantly separated. The population structure analysis, cluster analysis and principal coordinate analysis results were highly consistent, and it was concluded that the drought-resistant flax varieties had a high degree of genetic diversity, and it was most appropriate to divide the 29 drought-resistant flax varieties into 2 subgroups according to the analysis results.