Morphological and AFLP variation of Porphyra yezoensis Ueda form, narawaensis Miura (Bangiales, Rhodophyta)

Detailed morphological observations were made on two strains of cultivated Porphyra: HG‐1 (pure line isolated from Dai‐1) and Noriken‐4 (parental strain of a pure line HG‐4). The two strains were identified as P. yezoensis f. narawaensis based on their macroscopic and microscopic features, such as long linear or oblanceolate blades up to 50 cm in maximum length, division formulae of spermatangia and zygotosporangia, shape of trichogynes and carpogonia, and the second transverse divisional plane formed at the division from c/2 to c/4 in zygotosporangia. Gametophytic blades from two completely homozygous conchocelis strains isolated in this study (HG‐1 and HG‐4) were cultured under the same conditions and compared to confirm whether the differences in their shapes are genetically determined. The shape of blades from both of conchospores and monospores was always more slender in HG‐4 than in HG‐1 at the same blade age, suggesting that the difference in the blade shape between the two pure lines is due to genetic variation. To estimate the level of genetic variation the two pure lines were subjected to amplified fragment length polymorphism fingerprint analysis. A total of 230 bands were detected in HG‐1 and HG‐4 using eight selective primer pairs, and the number of polymorphic bands was only two in HG‐1. These results indicate that the two pure lines certainly show genetic variation, which is, however, at an extremely low level. The importance of pure‐line breeding and the origin of currently cultivated Porphyra are discussed. This is the first report to identify currently cultivated Porphyra strains in Japan based on combined results of detailed morphological observations and molecular analysis.