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SUMMARY We conducted a morphological observation and molecular phylogenetic analyses on bladed Bangiales collected from natural populations on Shikinejima Island and Hachijojima Island of the Izu Islands, southern central Japan. The morphological features of the gametophytic blades such as the blade shape, blade margin and reproductive cell divisions were extremely similar to those parameters of Neoporphyra haitanensis, a species cultivated in southern China, and Neoporphyra dentata. However, the blades collected from the two islands were thicker than the blades of N. dentata; this feature was the same as that of N. haitanensis. The chloroplast RUBISCO spacer sequences of present samples were identical to the sequences of N. haitanensis from China. Moreover, phylogenetic positions of three conchocelis strains isolated from the blades on the two islands were examined based on concatenated sequences of the chloroplast rbcL gene and nuclear 18S rRNA. The results showed that the strains were resolved in a clade including N. haitanensis; however, the strains were separated from N. haitanensis in China. Therefore, the bladed Bangiales from the two islands were identified as N. haitanensis. The present study is the first record of N. haitanensis in natural populations in Japan. [ABSTRACT FROM AUTHOR]

In the marine crop Pyropia yezoensis, a cross-fertilization experiment between a cultivated strain and cryptic species was carried out to investigate the possibility of polyploidy breeding using cryptic species. To perform the cross-fertilization, we isolated a green mutant strain (IBYC-G1) of the cryptic species by heavy-ion beam irradiation. The green mutant was crossed with a wildtype strain (HG-4) of P. yezoensis f. narawaensis. The F1 heterozygous conchocelis developed normally and released numerous conchospores. However, almost all the conchospore germlings did not survive past the four-cell stage or thereabout, and a few germlings developed into gametophytic blades. These results indicated that reproductive isolation occurred during meiosis and that P. yezoensis and cryptic species were different species using the biological species concept. Almost all the archeospores that were released from the surviving F1 blades developed into normal gametophytic blades. The result of nuclear DNA marker analysis revealed that the F1 blades that developed from both conchospores and archeospores were allodiploids in the haploid gametophytic phase. Although their F1 blades were extremely slender, their blade color was a deeper reddish brown as compared with that of P. yezoensis f. narawaensis, and the rate of blade length increase was remarkably higher in the blades of F1 than in those of the cryptic species. These results suggested that polyploidy breeding in the marine crop will attract more attention as a breeding method for further development of new cultivars. [ABSTRACT FROM AUTHOR]