Distribution of five growth hormone gene haplogroups in wild and cultured tench, Tinca tinca L., populations

Abstract

Tench, Tinca tinca L., has a growth hormone (GH) gene of 1758–1763 bp in length with at least 13 different haplotypes and 14 polymorphic sites (PS). Fragment length analysis at PS 1 and 7 with indels, and PCR-RFLP analysis at PS 5 and 13 with single nucleotide polymorphisms (SNPs) distinguish five GH gene haplogroups (H1-H3 belonging to the Western, W, and H4-H5, to the Eastern, E, phylogroup). Using quick and inexpensive screening assays, the aim of the study was to determine the allelic and genotypic distribution of the five GH gene haplogroups across 16 wild and cultured tench populations originating from all major parts of its distribution range. The mean observed number of haplogroups per population was 3.125. The most frequent haplogroup was H5 (0.482); the least frequent was H4 (0.022). The W haplogroups were observed in 12 out of the 16 populations, but no population had only the W haplogroup. With two exceptions (Ital and Kowa), the E haplogroups were observed in most populations as well as unique in three populations (Chin, Bada and Turk). Hardy–Weinberg equilibrium tests revealed heterozygote excess (P < 0.05) in four populations (Felc, ML98, Ta98 and Vo98) whereas heterozygote deficiency was not observed. Overall F-statistics showed quite a high degree of differentiation (P < 0.01) of tench populations, as the global FST was 0.212. The pairwise FST values ranged from 0.0 to 0.726. Non-significant differences between pairs of populations were observed in 41 cases (36.6%). Nei's standard genetic distances displayed large variations, ranging from 0.0 (between Bada and Chin) to 2.572 (between Turk and Ital). In some cases, similarities between populations from distant countries and dissimilarities between populations from the same country were observed. The Neighbour-Joining tree based on Nei's standard genetic distances showed two major clades corresponding with the observed frequencies of haplogroups within populations.