Genetic diversity and population structure among cultivars of Saccharina japonica currently farmed in northern China

Abstract

Close to 50% of the annual production of the brown alga Saccharina japonica, about 2 million tons (fresh weight), is produced through farming in Shandong province, China, principally around Rongcheng. Under artificial selection for phenotypic traits (e.g. color, blade length) cultivated strains (cultivars) face the problems of inbreeding depression, which can be caused by the close relationships of the parental plants. Hence, in an attempt to evaluate genetic variations and relationships among cultivars, 15 major farmed cultivars were selected and sampled from seven major hatcheries and analyzed using 15 microsatellite markers. A total of 94 alleles were found across all samples, with allele numbers ranging from three to 17 per locus. All of the cultivars exhibited relatively high levels of genetic diversity, with mean Nei's genetic diversity (H) and the Shannon's information index (I) of 0.466 and 0.862, respectively. A UPGMA dendrogram grouped all cultivars into three main clusters. However, two of the most commonly farmed cultivars (DB and BN) from different hatcheries failed to cluster together. Instead, differently named cultivars from the same hatchery tended to group together, implying that their high similarities is partly due to the presence of genetic mixing among cultivars within a hatchery or misuse of cultivar's names. Genetic analysis performed by Bayesian model-based clustering revealed clear differentiation of three major subgroups (LJ-202 and LJ-205; LJ-C033; XS-2 and XS-BN) and one admixed group (the remaining ten cultivars). Our results revealed ambiguous genetic relationships among certain cultivars of S. japonica farmed in northern China. A more stringent and prudent regulation should be applied during breeding and production process in the future.

Assessment of the Genetic Connectivity Between Farmed Populations on a Typical Kelp Farm and Adjacent Spontaneous Populations of Saccharina japonica (Phaeophyceae, Laminariales) in China

“…The genetic diversity of the farmed and spontaneous populations was consistent with those detected in the previous studies (Li et al, 2017;Shan et al, 2017;Zhang et al, 2017). Interestingly, the subtidal spontaneous populations exhibited lower genetic diversity than the farmed populations.…”

“…Meanwhile, the three farmed cultivars were demonstrated to be genetically close to each other. As was suggested and revealed in our previous studies, mixing among different cultivars were most likely caused by sharing of refrigerated seawaters during seedling production in the hatchery (Shan et al, 2011;Li et al, 2017). The result was the homogenization of genetic composition and agronomical features of the cultivars.…”

Genome-Wide SNP Markers Based on SLAF-Seq Uncover Genetic Diversity of Saccharina Cultivars in Shandong, China

“…Across the 13 Saccharina cultivars examined in this study, we observed that the highest He and Ho value is 0.295, which is lower than natural kelp population in Japan and Russia (Zhang et al, 2017). However, another study showed that the genetic diversity of cultivars group was higher than the natural kelp populations (Li et al, 2017). The AFLP analysis of cultured and wild population of kelp in Dalian coast showed that the level of genetic variation of two kinds of population has no significant difference (Wang, 2009).…”

Underpinning the Development of Seaweed Biotechnology: Cryopreservation of Brown Algae (Saccharina latissima) Gametophytes

“…[8][9][10] However, several Asian cultivars suffer from inbreeding depression, due to continuous ''selfing'' and limited crossbreeds from a restricted germplasm base. 11 There is a general trend of decreasing abundance of several native kelp species, including S. latissima, at their southern distributional range limits and increasing abundance in other parts of their distribution, mainly northward. 4,12,13 The founder effect of postglacial colonization in northern S. latissima populations suggests a lower intraspecific genetic diversity compared with populations from the southern range of distribution.…”