Genotyping‐by‐sequencing for construction of a new genetic linkage map and QTL analysis of growth‐related traits in Pacific bluefin tuna

Pacific bluefin tuna ( Thunnus orientalis ) has high market value, but its wild populations have decreased in recent years. The broodstock of Pacific bluefin tuna that were hatched artificially and reared under aquaculture conditions is beginning to be used for production. The creation of broodstock with commercially valuable traits, such as rapid growth, is therefore of great interest. Genetic linkage map‐based identification of markers associated with quantitative trait loci ( QTL s) facilitates marker‐assisted selection ( MAS ) breeding and allows efficient genetic improvement of broodstock. Single nucleotide polymorphism ( SNP )‐based genetic linkage map construction using the genotyping‐by‐sequencing method can expand the number of mapped markers and help identify growth‐related QTL s. In this study, we constructed sex‐specific maps for 24 linkage groups consisting of 677 SNP and 651 microsatellite markers. The total lengths of 93 progenies in the mapping population followed normal distribution, with an average length of 9.4 mm. We performed composite interval mapping in the mapping population. QTL analysis revealed one significant QTL in LG 10 on the female linkage map. The genetic linkage map—the second such map generated for Pacific bluefin tuna—and the growth‐related QTL s detected in this study will be useful for tuna aquaculture MAS programs.