About the project

Breed4Kelp2Feed aims to initiate breeding of sugar kelp (Saccharina latissima, a marine brown macroalgae) designed for sustainable production of high yields. In addition to providing food, feed and highly valued chemicals, cultivation of kelp contributes to carbon binding in the oceans.

• Background

  Cultivation of kelp is rapidly expanding worldwide, and Norway, with its extremely long coastline and well-established aquaculture industry, has a huge potential for value creation from kelp cultivation. Currently, only natural populations of kelp is cultivated in Norway, and there is a great potential to exploit genetic variation to produce material with improved characteristics from a cultivation and usage point of view, such as higher growth rate and biomass production, higher protein content, resistance to epiphytes or pathogenic organisms, low content of iodine or other minerals.

  Genetic improvement has been instrumental for establishing a cost-effective salmon industry in Norway, and breeding of kelp is likely to play a similar role for the future aquaculture industry. Kelps are important habitat-forming species in marine ecosystems, and measures to prevent any harmful effects of kelp cultivation on natural kelp populations must be considered and implemented if required. One such measure may be the development and cultivation of sterile, non-reproductive kelp that cannot hybridize with natural populations. 

• Objectives

  Our goals are to: 1) develop triploid and sterile sporophytes of S. latissima, 2) identify the most optimal breeding program for kelp, 3) test the feasibility and outcome of a simple breeding program based on local populations, and 4) obtain knowledge on the genetics of S. latissima. 

• More about the project

  Breed4Kelp2Feed is linked to the Centre of Research-based Innovation (SFI) Foods of Norway, based at NMBU. We are collaborating with Sintef Ocean, Seaweed Solutions and Flanders Research Institute on Agriculture, Fisheries and Food (ILVO) on this project.

• Final report

  Summary:

  Breed4Kelp2Feed aimed to lay the foundation for breeding of sugar kelp (Saccharina latissima, a marine brown macroalgae). In addition to providing food, feed, bioplastics, highly valued chemicals and more, cultivation of kelp contributes to binding of carbon and excess nutrients in the oceans. Cultivation of macroalgae is rapidly expanding worldwide, and Norway, with its long coastline, has a huge potential for value creation from cultivation. Currently, only natural populations of kelp are cultivated in Norway, and there is a great potential to exploit genetic variation to improve characteristics such as growth rate and biomass production and content of iodine or toxic minerals. Genetic improvement has been instrumental for establishing a salmon industry in Norway, and breeding may play a similar role for the future aquaculture industry. Kelps are important habitat-forming species in marine ecosystems, and measures to prevent harmful effects of kelp cultivation on natural kelp populations must be considered and implemented if required. One such measure may be the development and cultivation of sterile, non-reproductive kelp that cannot hybridize with natural populations. The project has brought us an important step towards realizing genetic breeding of kelp.

  We have studied published methods that have been used in genetic improvement of kelp in Asia and used one of these, mixed hybridization and mass selection, in a selection experiment over three generations. We studied the population genetics of the wild population forming the basis for the selection experiment. The population displayed high genetic diversity and a significant level of outbreeding. There was limited but significant genetic differentiation between several pairs of subpopulations separated by less than 2 km. Physical distance combined with information about ocean currents explained ~27% of the genetic variation. The molecular markers and methods developed in this work may be used in the future to monitor genetic changes in wild populations due to introgression from cultivated kelp or due to climate change, pollution or human activities in the ocean. 

  We studied the degree of selfing, apomixis (a form of asexual reproduction) and variation in reproductive success in the selection experiment. We conducted parentage analysis based on genomic information and discovered that in our experiment (i) some parents were unintentionally and strongly selected and were therefore overrepresented among the offspring, and (ii) there was a large proportion of highly inbred individuals, due to high rates of selfing and apomixis. Additionally, inbreeding had a strong negative effect on the size of offspring sporophytes. Firstly, these results suggest that some genotypes have higher fitness in the gametophyte-hybridization-establishment phase. These traits are interesting in themselves, however, if selecting for them in a breeding program, care must be taken to maintain sufficient genetic variation and to control for potential negative correlations with other traits of interest. Secondly, strategies to reduce the level of selfing and apomixis should be developed with regards to breeding programs building on mixed hybridization, although these phenomena may be utilized with success in other breeding strategies. Thirdly, selfing and apomixis may negatively affect the outcome of commercial propagation of seeding material.

  We have also conducted a thorough quantitative genetic analysis of the selection experiment, including genomic prediction of fresh weight, blade length, blade width and stipe length. Prediction accuracies were moderate (0.3-0.5) and bias very low. Narrow sense heritability estimates varied among the observed traits, with blade length and blade width exhibiting low heritability (0.2–0.3), while stipe length was highly heritable (0.5). Fresh weight showed no significant heritability but was strongly genetically correlated with blade length and blade width (r=0.8-0.9), which may therefore be used as a proxy for fresh weight in breeding. Despite selection for longer individuals, the average estimated breeding value for blade length did not increase, possibly due to strong unintended selection in the mixed hybridization set-up.

  We attempted to generate triploid sterile kelp through chromosome doubling of gametophyte cultures with colchicine. Triploidy has been used to produce sterile organisms before, and it may represent an important tool in kelp breeding aiming to avoid spreading to wild populations. While we did not succeed with this, we have gained useful knowledge and experience that we can use in the future. We established a method for determining nuclear DNA content in sugar kelp and documented that there is a lot of variation in DNA content during the life stages of kelps, especially within female gametophytes, and apparently also between individual gametophytes. In addition, there is variation among different tissue types in sporophytes.

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