In the present study onGracilaria sjoestedtii, 41 mutants (40 pigmentation and 1 morphological) were isolated. These were characterized in a Mendelian analysis, which showed that 26 of the pigmentation variants are recessive nuclear mutations. The remaining 14 are cytoplasmic mutants having maternal inheritance and no detectable transmission through spermatia. A partial complementation analysis identified seven cistrons among the nuclear pigmentation mutants. Multiple alleles were encountered at five loci and apparent intragenic recombination was observed. No linkage between cistrons was found in recombination tests conducted thus far. Mitotic recombination leading to diploid gametes on tetrasporophytes was observed and used to construct triploid tetrasporophytes. The chromosome number of a wild-type clone ofG.sjoestedtiiwas determined at meiosis asnensp;=ensp;29ndash;30. Trivalent chromosomes were observed during meiosis in tetrasporophytes obtained by crossing female plants with tetrasporophytes. In culture tanks with flowing seawater, female gametophytes grew faster and appeared more suitable for vegetative propagation than male gametophytes and tetrasporophytes.
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