Existence of an intact male life cycle offers a novel way in pure-line crossbreeding in the brown alga Undaria pinnatifida

Hermaphroditic gametophyte production and an intact male life cycle were investigated in Undaria pinnatifida. Zoospore-derived hermaphroditic gametophyte could give rise to male sporophytes which showed the same morphological appearance but with smaller biomass than normal cultivated sporophytes. Male sporophytes were shown to discharge only male zoospores. In this investigation, male spores derived from the male sporophytes and female spores derived from female parthenosporophytes were crossed to produce the hybrid sporophytic offspring. The latter contained both alleles of homozygous parental sporophytes when analyzed by use of eight polymorphic microsatellite markers, further confirming the success of cross. Thus, line crossing by use of unisexual sporophytes will be expected to replace unisexual gametophyte line crossing in breeding practice in the future in this commercially farmed seaweed.