Genetic control of morphogenesis in two varieties of Antithamnion plumula (Rhodophyceae, Ceramiales)

Abstract

Two morphologically distinct varieties of Antithamnion plumula have been studied in culture. The alga has a diplo-haplontic life history of the Polysiphonia type. The two varieties, var. plumula and var. bebbii which differ in the arrangement of branches, are interfertile, and the variation in F1and F2hybrids was studied to reveal the genetic control of branching. Progeny were studied by tetrad analysis and by random sampling of spore germlings. The heterozygous tetrasporophytes are always of the var. plumula phenotype. By meiosis in the tetrasporangium initials the two varieties are produced in equal numbers. The results are explained by assuming that a single gene is involved, represented by the dominant allele in var. plumula and by the recessive allele in var. bebbii.