Genetic analysis of artificial green and red mutants of Porphyra yezoensis Ueda (Bangiales, Rhodophyta)

Two artificial pigmentation mutants of Porphyra yezoensis, the green mutant IBY-G1 and the red mutant IBY-R1, were genetically characterized based on the results of cross experiments. The cross between the green mutant and the wild-type HG-511 and the cross between the red mutant and the wild type respectively produced the wild-type heterozygous conchocelis. Zygotospores from the heterozygous conchocelis developed into sectored F1 gametophytic blades (chimeras) in high frequency composed of parental color sectors in both crosses. The segregation ratios of the wild-type sectors and the mutant (green or red) sectors were approximately 1:1. These results suggest that both the green mutant and the red mutant are controlled by a single recessive nuclear gene. The reciprocal cross between the green mutant and the red mutant also produced the wild-type heterozygous conchocelis that is considered to be a dihybrid resulting from complementation of the green mutant gene and the red mutant gene. Zygotospores from the heterozygous conchocelis also produced sectored F1 gametophytic blades in high frequency composed of parental color (green and red) sectors and non-parental color (wild-type and yellowish green) sectors. The segregation ratios of parental color sectors and non-parental color sectors were approximately 1:1. Therefore, it is inferred that the green mutant gene and the red mutant gene are on different chromosomes, and that the wild-type and the yellowish green color sectors are produced by chromosome recombination. These genetic analyses demonstrate that the two artificial mutants are useful as genetic markers for cross breeding of cultivated Porphyra.