DNA Barcoding and Intronic-ORF Structure Analyses of Cultivated <i>Pyropia yezoensis</i> in China: The Genetic Impact under Climate Change

<i>Pyropia yezoensis</i> is the most widely cultivated and economically important alga. Affected by climate change, the cultivation of <i>P. yezoensis</i> has gradually migrated to the northern coast of China, increasing from 6.8% in 2019 to 19.5% in 2023. To date, the genetic impact of northern migration on cultivation resources has not been assessed and analyzed extensively. Here, DNA barcoding (<i>rbc</i>L and <i>cox</i>1) and the presence/absence of intronic-ORFs in mitochondrial regions (<i>rnl</i> and <i>cox</i>1) were applied to investigate genetic diversity in 44 <i>P. yezoensis</i> specimens from 17 aquaculture farms in China, with comparisons to Korean and Japanese cultivated resources. The lower intraspecific variation was 0.31% for the <i>cox</i>1 gene and 0.14% for the <i>rbc</i>L gene, with three haplotypes, indicating that intensive selection and breeding during cultivation had narrowed the germplasm genetic variation. The intron structure of mitochondrial regions showed that the cultivated resources had 17 phenotypes, and the northern specimens shared 35.3% of genotypes with the southern specimens, indicating that the cultivated <i>P. yezoensis</i> is expanding its cultivation ranges through north migration. Even with lower genetic diversity, the northern area of cultivation had already developed 17.6% site-specific specimens. The genetic diversity of cultivated <i>P. yezoensis</i> from the Northwest Pacific is also discussed. Our work provides a preliminary framework for <i>P. yezoensis</i> breeding and cultivation under climate change.