Mapping of quantitative trait loci for growth traits around the first overwintering period in Songpu mirror carp (Cyprinus carpio L.) cultured in Northeast China

QTL mapping studies of growth traits based on high-density linkage maps in Northeast China has great significance for local enterprises in achieving MAS and improving the selection accuracy of parent fish. Here, we constructed a high-density genetic linkage map with 11,445 single nucleotide polymorphism (SNP) markers in a full-sib F1 family consisting of 120 progenies in Songpu mirror carp (Cyprinus carpio) reared in Northeast China. The consensus map covered 5471.93 centimorgans (cM) across the 50 linkage groups with an average resolution of 0.54 cM. Around the first overwintering period, a total of 15 QTLs for growth traits were identified on five LGs (LG7, LG8, LG14, LG30, and LG41). All of them were responsible for body weight (BW) at both 150 (before overwintering) and 350 (after overwintering) days, explaining 9.8-17.9 % of the phenotypic variation (PV). Two major-effect QTLs were detected on LG30, which explained 16.5 % and 16.4 % (qTL9-30), and 15.8 % and 17.9 % (qTL10-30) of the PV at 150 and 350 days, respectively. In addition, 15 loci were identified for 4 growth traits other than BW at both time points, including 6 loci for body length (BL), 7 loci for body height (BH), 3 loci for body thickness (BT) and 5 loci for head length (HL). These loci explained PV ranging from 15.9 % to 21.2 % for BL, 9.3-19.6 % for BH, 9.6-15.5 % for BT, and 10.6-18.1 % for HL. Nine candidate genes (IGF1b, LEPb, PACAP1a, GHSR1a, PPSS2, IRS1, APOAIb, IRS2b and ADSS1) were identified, five of which were directly related to growth hormone (GH), including IGF1b, PACAP1a, GHSR1a, PPSS2 and IRS1. Notably, three genes (GHSR1a, PPSS2 and IRS1) were derived from two major-effect QTLs (qTL9-30 and qTL10-30). In conclusion, these novel findings may shed light on early selection of growth traits of common carp cultured in Northeast China and other relatively high-latitude regions.

Automated summary

QTL mapping studies of growth traits based on high-density linkage maps in Northeast China are of great significance for local enterprises. A high-density genetic linkage map was constructed, and 15 QTLs for growth traits were identified, which explained 9.8-17.9% of the phenotypic variation. Two major-effect QTLs were found, along with 15 loci for other growth traits. Nine candidate genes, including five genes related to growth hormone, were identified. These findings provide insights into early selection of growth traits in common carp cultured in Northeast China and other high-latitude regions.