Induction and isolation of pigmentation mutants in Pyropia suborbiculata Kjellman (Bangiales, Rhodophyta)

In order to obtain the artificial pigmentation mutants, a certain dose of ultraviolet ray was used to irradiate the gametophytic blades developed from conchospores of the wild-type strain in Pyropia suborbiculata. Color-mutated cells of showing light green yellow, olive, green, green brown, yellow brown, light brown, dark purple red and light purple red and other mutated colors appeared in the UV-irradiated blades after being cultured of 7 to 14 d. These color-mutated cells grew to form different color cell-clusters after being cultured for an additional 2 to 3 weeks. The frequency of appearing color-mutated cell-clusters on the gametophytic blades increased with increasing intensity of ultraviolet irradiation from 0-80 μW/cm². However, as the radiation intensity increased to 100 μW/cm², the frequency of appearing color-mutant cell-clusters decreased on gametophytic blades. These results indicate that 80 μW/cm² is most effictive intensity of ultraviolet irradiation for inducing mutations of gametophytic blades in Pyropia suborbiculata. The color-mutated cell-clusters were cutted, placed in aerating culture bottle and cultured, until they released monospores. The nylon cotton thread was placed into aerating culture bottle and used for monospores adhering matrix. Monospores on the cotton thread were cultured, and germinated into blades. From the blades arising from germination of monospores, yellow brown, olive, red, brown red, and other single-colored mutant blades were selected. Subsequently, the respective genetic homozygous conchocelis (strains) were obtained using the gametophytic blades parthenogenesis. Their colors were relatively stable in both F₁ gametophytic blade and conchocelis phases. The F₁ gametophytic blades of each mutant strains from conchospores are the same color as the respective parent blades, indicating that the color is stably inherited. In vivo absorption spectra and contents of chlorophyll a, phycoerythrin and phycocyanin of F₁ gametophytic blades from conchospores of pigmentation mutant strains and the wild-type strain in Pyropia suborbiculata were measured. The results show that, compared with wild-type strains, the growth rate, the in vivo absorption spectrum, the contents of the three main photosynthetic pigments and pigment proteins, and their ratios to each other are changed significantly in the F₁ gametophytic blades of each pigmentation mutant strains.