A major hurdle in the path of economically feasible kelp farming, at the scales needed to reshape crop markets, is the environmental concerns raised by the possibility of invasive species and trans gene flow; offshore farms are often close to marine protected areas, recreational areas and shipping channels. Trans gene flow is associated with many of our current terrestrial crops which are essentially non-native (e.g. wheat), being originally domesticated and improved in one region and then transplanted across the globe. New crops, including aquaculture crops, are held to more stringent standards to minimize the risks from invasive species and trans gene flow in order to protect native plants, and treasured natural or heritage populations. What potential solutions might allow domesticated genomically improved strains of kelp to be grown safely in natural areas? We propose to establish kelp strains with a completely sterile sporophyte stage. The haplodiplontic life cycle of kelp makes them remarkably well-suited for this kind of manipulation. The large sporophyte fronds are the generation that is harvested as a crop, but the microscopic haploid kelp gametophyte generation may be vegetatively propagated indefinitely in culture. We will identify natural alleles, i.e. recessive mutations (loss-of-function) in genes required for meiosis. Male and female gametophytes with these recessive sterile mutations can still produce gametes that can be crossed to produce fully sterile sporophytes (because gametes are produced by mitosis in the gametophyte generation, not meiosis). This allows for the fast, targeted selection of immortalized gametophytes.