Exploration and growth characteristics of allopolyploids derived from interspecific hybridization between Neopyropia yezoensis and Neopyropia tenera (Bangiales, Rhodophyta) in natural populations of eastern Japan

Abstract

We investigated the distribution of allopolyploids of the red algal genus Neopyropia (referred to as nori) in natural populations of eastern Japan and compared the growth characteristics of allopolyploids and ancestral species under laboratory culture. To detect hybrids between Neopyropia yezoensis and Neopyropia tenera, 99 samples collected from 7 localities were examined by sequence analysis of the chloroplast RUBISCO spacer region and DNA marker analyses of two nuclear genes. The results indicated that 20 samples were hybrids derived from interspecific hybridization between the two species. Using 5 conchocelis strains among the hybrids, the blades that developed from both conchospores and archeospores were obtained under laboratory culture and were examined by nuclear DNA marker analyses to confirm allopolyploidy. As a result, the five strains were confirmed as allopolyploids derived from interspecific hybridization between N. yezoensis as the maternal strain and N. tenera as the paternal strain. Furthermore, from two of the five strains, the allopolyploid strains TUYTA-7 and TUYTA-8 were established via self-fertilization of the blade from an archeospore, and the blade growth and photosynthetic pigments of the two strains were compared with those of the strain UM-T55 of the ancestral species N. tenera collected from the same origin site as the two strains. In the allopolyploid strains, the TUYTA-8 blades exhibited superior characteristics, such as a long and linear shape, rapid elongation, low fertility and high pigment content. These results imply the importance of exploring and isolating more allopolyploid strains in bladed Bangiales. Moreover, it is possible that polyploid breeding due to interspecific hybridization in the bladed Bangiales will become more popular as a practical method for developing new cultivars of nori.