Improving seedless kelp (Saccharina japonica) during its domestication by hybridizing gametophytes and seedling-raising from sporophytes

Abstract

Dongfang no.7 (Saccharina japonica) was bred and maintained by hybridizing gametophytes, self-crossing the best individuals, selecting the best self-crossing line and seedling-raising from yearly reconstructed sporophytes. It increased the air dry yield by 43.2% in average over 2 widely farmed controls. Dongfang no.7 was seedling-raised from bulked sporophytes reconstructed from its representative gametophyte clones. Such strategy ensured it against variety contamination due to possible cross fertilization and occasional mixing and inbred depletion due to self-crossing number-limited sporophytes year after year. It derived from an intraspecific hybrid through 4 rounds of self-crossing and selection and retained a certain degree of genetic heterozygosity, thus being immune to inbred depletion due to purification of unknown detrimental alleles. Most importantly, it can be farmed in currently available system as the seedlings for large scale culture can be raised from reconstructed Dongfang no.7 sporophytes. Breeding and maintaining Dongfang no.7 provided a model that other varieties of kelp (S. japonica) and brown algae may follow during their domestication.

The Environmental Risks Associated With the Development of Seaweed Farming in Europe - Prioritizing Key Knowledge Gaps

“…Cultivated seaweeds will most likely be characterized by a human imposed shift in their reproductive strategy (e.g., from outcrossing to self-fertilizing and from sexual reproduction to vegetative reproduction) introducing genetic bottlenecks that may narrow the genetic diversity of cultivated stands potentially making them more susceptible to environmental changes and disease as observed in vegetative propagation of domesticated Gracilaria (Leonardi et al, 2006;Valero et al, 2017). Studies have resulted in the production of improved varieties of kelps with respect to commercially valuable traits (e.g., stipe length, frond length, width and thickness, and iodine content) (Liu et al, 2014;Li et al, 2016) and these have been widely applied in cultivation activities (Li et al, 2007(Li et al, , 2008(Li et al, , 2016. The consequences of producing cultivars that are genetically and phenotypically distinct from natural populations is unknown but there is the potential for significant environmental effects through both direct competition with wild populations and hybridization with natural stands (Halling et al, 2013;Loureiro et al, 2015;Valero et al, 2017).…”

Macroalgal germplasm banking for conservation, food security, and industry

“…This stage is optimal for preservation because of its evolved traits that facilitate longterm dormancy in natural conditions (e.g., nutrient-rich endosperm, robust seed coat, specific germination requirements) [38]. Conversely, algal germplasm banking (referred to as biobanking elsewhere) more resembles methodology utilized for long-term storage of nonflowering land plants where either spores or haploid gametophytes are stored [39][40][41][42]. However, the cells or tissues targeted very much depend on the species, as the longevity of seaweed microscopic stages is related to the seaweed life strategy that will resume development when returned to adequate conditions [43].…”

“…Furthermore, the culturing techniques and hatchery methods have been well developed for a variety of species, particularly for economically important species (e.g., Chondracanthus chamissoi [49], Porphyra yezoensis [50], Saccharina spp. [40,51]), but long-term storage protocols are less commonly available. Thus, we recommend that liquid cultures held under dormancy conditions (e.g., reduced light and temperature) be prioritized for long-term germplasm preservation as a methodology that can be more quickly implemented given the current availability of algal preservation protocols.…”

“…Major challenges of documenting genetic diversity across distributions have included not only considerable collection costs but, historically, impeding sequencing costs as well. However, work done over the past 30 years with increasingly economical sequencing approaches has made important progress in our understanding of genome evolution, genetic diversity, population structure, and ecosystem dynamics in commercially and ecologically important macroalgae (e.g., Macrocystis [6,66,[85][86][87][88][89], Porphyra [62,[90][91][92][93][94], and Saccharina [40,51,95]). A well genotypically characterized germplasm bank can provide a wealth of information for macroalgal varieties, breeding lines, and has been developed for several strains in Asia and is currently underway at several facilities in North America and Europe [96].…”

Assessment of genetic and phenotypic diversity of the giant kelp, Macrocystis pyrifera, to support breeding programs

“…Under this scenario, seaweed farming requires the urgent development of breeding programs to increase yield and optimize other relevant agronomic traits [9,10]. There is a large amount of information on the development of macroalgal strains in red and brown algae [11,12,13]. However, the genetic science behind seaweed breeding and domestication is still in an initial phase, with little conceptual and empirical progress [14].…”