Genetic polymorphism within Porphyra yezoensis (Bangiales, Rhodophyta) and related species from Japan and Korea detected by cleaved amplified polymorphic sequence analysis

We investigated genetic diversity in 10 strains of Porphyra yezoensis and related species, collected from Japan and Korea, in order to identify an appropriate crossing partner for use in various genetic analyses. Firstly, the phylogenetic relationships among the 10 strains were examined using SSU rDNA sequences. All five Japanese strains (TU-1, TU-2, TUH-25, JHS and JHU) and two of the Korean strains (KGJ and KPH) were identified as P. yezoensis while the other three Korean strains (KTY1, KTY2 and KTY3) were identified as P. tenera. Using cleaved amplified polymorphic sequence analysis, genetic polymorphisms lying in five regions of four genes (beta-tubulin, TOP2, EF-1 alpha and V-ATPase) were examined. Twenty out of 34 restriction endonucleases revealed genetic polymorphisms between the seven strains of P. yezoensis and the three strains of P. tenera in all five regions tested. Furthermore, when they were employed to digest the fragments of TOP2 and V-ATPase, 14 enzymes discriminated the two Korean strains of P. yezoensis (KGJ and KPH) from the five Japanese strains of this species. The level of polymorphism was much higher in the amplified fragment of V-ATPase (including four introns) than in that of TOP2 without an intron. The gene regions with detected polymorphisms would be useful molecular markers for confirmation of cross-fertilization in sporophytic thalli and for construction of a linkage map. A suitable combination of the strains in the cross experiment is discussed.