Comparison of partial nucleotide sequences in the exonic region of a small subunit ribosomal RNA gene for discrimination of laver (Porphyra) species and cultivars

Partial nucleotide sequences in the exonic region of a small subunit ribosomal RNB gene (ssr DNA) were analysed for nine commercially utilized species of Porphyra and eight lever cultivars in order to examine whether these sequences can be used to identify and discriminate between these species and cultivars. Pairwise comparisons of a total of 555 nucleotides revealed that there were from one to ninety-one nucleotide differences (substitutions and insertions/deletions) among the nine species. The one nucleotide difference found between Porphyra yezoensis and P. tenera was authentic, confirmed by repetitive sequence analyses of ssr DNA exonic regions using thalli of these species collected from five different locations. The nucleotide sequences of eight laver cultivars were identical to each other and also identical to field-collected P. yezoensis but not P. tenera. These results suggest that the nine Porphyra species can be distinguished from each other by comparison of the partial nucleotide sequences of the ssr DNA exonic region, while discrimination of laver cultivars is not possible by the comparison of only these sequences.