Genetic analysis of the gametophytes of Undaria pinnatifida (Phaeophyceae) with ISSR method

Inter-simple sequence repeat (ISSR) analysis was used to assess eleven pairs of Undaria pinnatifida (Harv.) Suringar male and female gametophytes. After screening fifty primers, 18 ISSR primers were selected for final analysis. A total of 104 loci were obtained, of which 77 were polymorphic among the gametophytes studied. Genetic relationships were analyzed with simple matching (S), Jaccard's (J) and Dice's (D) distance coefficients. Little genetic variations were found among the selected Undaria gametophytes, for instance, the genetic distances ranging from 0.010 to 0.125 with Dice coefficients. UPGMA dendrograms showed that 11 pairs of Undaria gametophytes were distributed into five groups. Most Undaria strains cultivated in China exhibited closely genetic relationships with the strains from Japan. However, gametophytes from Qingdao appeared as distinct clades from other Undaria strains with all three distance coefficients used. Mantel test showed that the three distance measurements generated congruent clustering patterns on the same data. Our results demonstrated the feasibility of applying ISSR markers for genetic analysis of Undaria gametophytes.