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

Partial nucleotide sequences in the exonic region of a small subunit riboso mal RNB gene (ssr DNA) were analysed for nine commercially utilized species of Porphyra and eight lever cultivars in order to examine whether these se quences 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 an d insertions/deletions) among the nine species. The one nucleotide differen ce found between Porphyra yezoensis and P. tenera was authentic, confirmed by repetitive sequence analyses of ssr DNA exonic regions using thalli of t hese species collected from five different locations. The nucleotide sequen ces of eight laver cultivars were identical to each other and also identica l to field-collected P. yezoensis but not P. tenera. These results suggest that the nine Porphyra species can be distinguished from each other by comp arison of the partial nucleotide sequences of the ssr DNA exonic region, wh ile discrimination of laver cultivars is not possible by the comparison of only these sequences.