The wild relatives of the cultivated Saccharina japonica belong to the genus Saccharina, with S. cichorioides serving as an essential source of wild germplasm for kelp breeding due to its superior tolerance and higher polysaccharide content. However, the limited understanding of its population structure and genetic diversity often results in increased operational costs and longer breeding processes.

To address this issue, a research team led by Prof. DUAN Delin from the Institute of Oceanology of the Chinese Academy of Sciences (IOCAS), in collaboration with researchers from Japan and Russia, investigated the genetic background of this important wild crop relative.

The findings were published in the journal Aquaculture.

In this study, 13 populations of S. cichorioides, combined with five other species from the Saccharina genus, were used to assess genetic diversity, population structure, and evolutionary history. The analysis was based on the mitochondrial marker COI and nine microsatellite markers.

The researchers identified that S. cichorioides can be divided into two distinct groups, which show significant genetic differentiation and limited gene flow. Populations along the coast of the Sea of Japan (the JPS group) exhibit high levels of genetic diversity, while populations from the east coast of Sakhalin Island (the OKS group) represent ancient populations.

Among the six species studied, S. cichorioides showed the highest haplotype and nucleotide diversity, indicating significant genetic differentiation among these wild relatives.

Gene flow analysis revealed no gene introgression between the JPS and OKS groups. The researchers inferred that the Soya Strait may serve as a barrier, limiting genetic exchange between the populations of S. cichorioides.

Furthermore, it was found that the highest levels of genetic diversity were predominantly in populations located along the shoreline of the Sea of Japan.

This study enhances our understanding of the population patterns of S. cichorioides and may provide guidance for the collection of wild germplasm and the protection of resources.

Relationship and geographical distribution of S. cichorioides and its closely related species. (Image by IOCAS)