Identification, growth, and pigment content of a spontaneous green mutant of Pyropia kinositae (Bangiales, Rhodophyta)

Abstract

A green-colored gametophytic blade of wild Pyropia was found in a natural population in the estuary area of the Naruse River, northeast Japan. To identify the isolated green mutant strain K-G1 and the wild-type strain K-1 derived from the same population, we carried out morphological observations and molecular analysis of the RUBISCO spacer region and the rbcL gene. As a result, the two strains were identified as Pyropia kinositae, which is a species closely related to the marine crop Pyropia yezoensis. Under the same laboratory culture, the growth and pigment contents of the green mutant K-G1 were compared with those of the wild-type K-1. The growth of the conchocelis and gametophytic blade tended to be slower in the green mutant than in the wild type, although differences in their growth were not apparent in some of the temperature conditions examined. Maturation of the conchocelis and blade in the two strains was fastest at 20 °C among the temperature conditions examined (5–25 °C). The phycoerythrin content was significantly lower in the green mutant than in the wild type. Additionally, the color phenotype of the green mutant was genetically stable in both the sporophytic conchocelis and gametophytic phases. Because the color of a pigmentation mutant facilitates cross-confirmation as a genetic marker in monoecious Pyropia species, these results suggest that the green mutant of P. kinositae will contribute as new breeding material for cross-breeding and polyploidy breeding in Pyropia.