Comparative analysis of morphometric traits of farmed sugar kelp and skinny kelp, Saccharina spp., strains from the Northwest Atlantic

Our team has initiated a selective breeding program forregional strains of sugar kelp,Saccharina latissima, toimprove the competitiveness of kelp farming in the UnitedStates. Within our breeding program, we also include anendemic putative species,Saccharina angustissima, locallyreferred to as skinny kelp. We crossed uniclonal gameto-phyte cultures derived from 37 wild-collected blades rep-resenting five sugar kelp strains and one skinny kelp strainto produce 104 unique crosses. Each cross was outplantedon a near-shore research farm located in the Gulf of Maine(GOM). After the first farming season, our results indicatedthat sugar kelp and skinny kelp were interfertile, and pro-duced mature and reproductively viable sporophytes. Mor-phological traits of individual blades varied depending onthe parental contribution (sugar vs. skinny), with significantdifferences found in progeny blade length, width, thickness,and in stipe length and diameter. Despite these differences,wet weight and blade density per plot showed no statisticaldifferences regardless of the cross. Given their publishedgenetic similarity and their interfertility shown here,S. angustissimaandS. latissimamay not be different species, and may each contribute genetic diversity to breeding pro-grams aimed at meeting ocean farming and market needs.