Variation in the numbers of silver-stained nucleolar organizer regions (Ag-NORS) were examined in 36 breeds of domestic pig of different geographic origins and five subspecies of wild boar. The relationship between Ag-NORs and evolution of domestic pigs was investigated. In all pigs observed, Ag-NORs were localized on the secondary constriction of chromosomes 10 and 8. The mean Ag-NOR numbers varied from 2.0-4.0, and decreased gradually with the different geographical distribution from south to north in China and from east to west in Europe. This regular change was caused mainly by the differences of frequency in chromosome 8 Ag-NOR type and was closely related to the evolution of domestic pig breeds.

Neopyropia yezoensis is a typical intertidal seaweed and a major mariculture crops in China. The culture area of N. yezoensis has been largely increasing in the past decade. Whether large-scale cultivation of N. yezoensis has a genetic impact on wild populations remains unknown. Here, eleven polymorphic microsatellite markers were developed and applied for the genetic structure analysis of 22 N. yezoensis populations from along the coast of China. The populations were divided into 4 groups based on the Bayesian model-based structure analysis. A significant genetic structure difference was present between the cultivated populations and the wild ones. The 13 wild populations were divided into two distinct groups, with no obvious correlation between the inter-population genetic variation and geographical distance within each group. The average polymorphism of 9 cultured N. yezoensis populations was higher than that of the wild populations, and the percentage of polymorphic loci of the most cultivated populations was at a high level (P=90.91%). It indicated that the germplasm of cultivated N. yezoensis in China are diversified. The genetic differentiation between the cultivated populations and the wild populations decreased with the increasing cultivation time. But the gene flow between the cultivated populations and the wild ones was asymmetric, exhibiting a trend from wild population to cultured population. The result indicated that even if there is a genetic impact of N. yezoensis aquaculture on wild resource, it is a long-term and slow process. This research provided useful insights for future germplasm resource evaluation and genetic breeding of N. yezoensis.

The purpose of this study was to develop stable microsatellite markers and evaluate the genetic background of cultivated Sargassum fusiforme. Based on the transcriptome data obtained by high-throughput sequencing, eleven polymorphic microsatellite markers were developed using four S. fusiforme populations from China. One cultivated population was from Dongtou (DT) and three wild populations were from Muye Island (MY), Pingyu Island (PY) and Nanji Island (NJ). The cultivated S. fusiforme had the highest genetic diversity, with 90.91% polymorphic loci and Shannon’s information index (I) of 0.606, which were much higher than those of the wild populations (I = 0.425). The four populations were divided into two groups through a structure analysis. DT, PY and NJ were clustered into a group, and MY was an almost completely separate group. Both the structure and principal coordinates analysis showed that DT and PY had the lowest genetic differentiation, suggesting that the parents of the breeding population in Dongtou partly come from Pingyu Island. The observed heterozygosity of NJ was much higher than expected, indicating that the NJ wild resource was greatly affected by the environment. These eleven microsatellite markers could provide additional markers for germplasm resource evaluations and facilitate genetic analyses of the S. fusiforme population.

Neopyropia yezoensis is a typical intertidal seaweed and an indispensable species for conservation of seaweed resources. As one of the most important marine vegetables, the cultivation area of N. yezoensis has been largely increasing in the past decade and ranked the second highest among all the farmed seaweeds in China. It remains unknown whether large-scale cultivation of N. yezoensis has a genetic impact on wild populations. In this study, SSR markers and 18S rDNA were applied for diversity and genetic structure analysis of 22 N. yezoensis populations from North China. Twenty-two haplotypes were generated from 352 18S rDNA sequences and only three haplotypes were shared by both cultivated and wild populations. Based on 11 polymorphic SSR markers developed, the average polymorphism of the cultivated N. yezoensis populations was higher than that of the wild populations, with the percentage of polymorphic loci being 90.91% in most cultivated populations. The cultivated populations were clustered separately from the wild ones based on the population phylogenetic tree. This indicates that cultivated N. yezoensis populations are diverse and divergent from wild populations in China. However, there were cultivated individuals mixed with the wild ones based on the individual phylogenetic tree and STRUCTURE analysis. The genetic differentiation between cultivated and wild populations decreased with increasing cultivation time, suggesting a possible long-term and slow process of genetic introgression between cultivated N. yezoensis and the wild resource. The wild populations were grouped into two distinct clades by SSRs, with one distributed around the intersection between the Yellow Sea and the Bohai Sea, where the populations were characterized by a specific 18S rDNA haplotype. These findings provide useful insights into germplasm conservation, genetic breeding and improvement of N. yezoensis farming practices.