Phenomenon of cell breakdown and phenotypic observation on surviving blades in inter-species hybridization progeny between pigment mutants of Pyropia haitanensis and P. acanthophora (Bangiales, Rhodophyta)

Abstract

Pyropia haitanensis is a species of red algae native to China. Its meiosis occurs during the first two divisions of germinating conchospores and a tetrad with different genotypes is formed in the second division. Then each cell continues to undergo mitosis and finally, the conchosporeling develops into a genotype chimeric blade. Conchospores were formed from the inter-species hybridization between a red-type pigmentation mutant of P. haitanensis and a green-type pigmentation mutant of Pyropia acanthophora, among which, a phenomenon of serious cell breakdown occurred in the early developmental stage of germination. The phenomenon of cell breakdown occurred not only in the direct products of meiosis (conchosporelings containing 2–4 cells), but also in conchosporelings whose cell number was more than four, but large-scale cell breakdown occurred in conchosporelings containing 3–4 cells. After 35 days in culture, 99.2% of conchosporelings was unable to form thallus due to the heavy breaking down of somatic cells and only about 0.8% of the conchosporelings could form thallus, but most of them could not develop from the complete tetrads but just developed from 1 to 2 surviving tetrad cells. The F1 gametophytic blades developed from conchospores showed two parental colors (R and G) and four new colors (R’, redder in color than R; G’, lighter in color than G; T, tawny in color; W, light brown in color). The results confirmed that the hybrid breakdown of Pyropia could not only be used to assist in the more accurate identification of species; but also could be used to select new strains with recombination advantage from the surviving offspring.