A novel diplotype in the GH gene associated with body weight traits around the first overwintering period in common carp (Cyprinus carpio L.) cultured in Northeast China

Common carp cultured in Northeast China need at least 3 or 4 years to become sexually mature. Consequently, in regard to local seed production enterprises, increasing selection accuracy with excellent growth potential has vital significance for lowing the cost of culturing and maintaining parent fish. In this study, a single nucleotide polymorphism (SNP) (g.1597C > A) and a 4-bp insertion-deletion (indel) (g.1609-1612, CTTC) in intron 3, and three synonymous SNPs (g.1630A > T, g.1669A > T and g.1672C > T) in exon 4 were identified in the growth hormone (GH) gene of common carp. Furthermore, a polymerase chain reaction-single strand conformation (PCR-SSCP) approach was constructed. Four haplotypes (H1, H2, H3 and H4) and ten diplotypes (H1H1, H2H2, H3H3, H4H4, H1H2, H1H3, H1H4, H2H3, H2H4 and H3H4) were detected in three carp breeds, including Heilongjiang carp Cyprinus carpio haematopterus (YL), a selective strain of German mirror carp Cyprinus carpio L. mirror (JL), and a cold-resistant strain of Purse red carp Cyprinus carpio var. wuyuanensis (HL). To reveal the associations of each diplotype with growth traits around the first overwintering period, a total of 747 individuals from YL (n = 263), JL(n = 229), and HL (n = 255) were genotyped. We found that fish with the H2H2 diplotype exhibited higher body weight (BW) (135, 325, 385 and 445 d) and net weight (NW) (445 d) than those with the H1H1, H1H2 and H2H3 diplotypes in YL (P < .05). In HL, there was a significantly lower overwintering weight loss rate (WLR) at 325 d and higher BW385, BW445 and NW445 in fish with the H2H2 diplotype than in those with the H1H2, H1H3, H2H3, H2H4, H3H3 and H4H4 diplotypes (P < .05). Taken together, these data unravel a novel H2H2 diplotype with positive effects on body weight traits around the first overwintering period, which should be used as a potential marker to improve accuracy of selection in common carp in Northeast China.