A research team led by Prof. PANG Shaojun from the Institute of Oceanology of the Chinese Academy of Sciences (IOCAS), along with collaborators, has reported on the challenges of genetic homogeneity in aquaculture of the kelp Saccharina japonica.

Their study, published in Aquaculture Reports, highlights a significant issue of genetic homogeneity among farmed cultivars of Saccharina japonica across China. This problem was first identified in Rongcheng, Shandong Province, a major region for kelp cultivation. Over a decade, the researchers conducted follow-up investigations and found that among the six main kelp cultivars analyzed, five exhibited persistent genetic uniformity. Only one hybrid cultivar displayed substantial genetic diversity.

Using molecular marker technologies and conducting open-sea cultivation trials, the team identified standardized parental selection and uniform seedling production processes as key factors contributing to this genetic uniformity. However, they discovered that introducing genetically distinct external germplasm through targeted hybridization breeding significantly improved genetic diversity and productivity. Notably, a newly developed cultivar, "205–24," demonstrated enhanced resistance to early sporulation, reducing sori formation rates from 70% to 28% at harvest, which greatly enhances its economic value.

The researchers underscored that genetic uniformity increases the susceptibility of kelp to diseases and environmental stress. This was evident during a severe kelp mortality event in Rongcheng between 2021 and 2022, where only a few hybrid cultivars survived. This situation highlights the urgent need to maintain genetic diversity in kelp aquaculture.

Prof. PANG stated, "We suggest that kelp farming enterprises establish independent, sustainable breeding systems and effective parental management processes, enhance genetic monitoring, and strategically introduce diverse external germplasm." These measures can help mitigate the risks of genetic drift and inbreeding, ensuring the long-term sustainable development of China's kelp industry.

Full stage-covered Saccharina seedlings and cultivation production cycle in China. (Image by IOCAS)