Construction of a genome-wide linkage map and QTL mapping for growth and hypoxia tolerance traits in Chinese longsnout catfish (Leiocassis longirostris)

The Chinese longsnout catfish (Leiocassis longirostris) is an important freshwater aquaculture species, and the selective breeding of fast-growth and hypoxia tolerance population will have a positive impact on its industry. In order to promote the breeding process of Chinese longsnout catfish, construction of the genetic linkage map and identification of molecular markers associated with fast-growth and hypoxia tolerance is critical for the marker-assisted selection (MAS) of Chinese longsnout catfish. In the present study, whole-genome resequencing was used to construct a high-density genetic linkage map of the Chinese longsnout catfish. The map containing 2946 bin markers was distributed over 26 linkage groups (LGs) with a total genetic coverage of 1980.76 cM and an average density of 0.67 cM. Based on the genetic map, quantitative trait locus (QTL) mapping results suggested that 17 QTLs associated with growth traits and 1 QTL associated with hypoxia tolerance were identified in eight LGs with the phenotypic variability explained (PVE) ranged from 5.1 % to 9.3 %. Four SNP loci from these QTLs were associated with the phenotypic traits validated by Kompetitive Allele Specific PCR or Sanger sequencing. In addition, the expression of three candidate genes for growth traits and five candidate genes for hypoxia tolerance was examined in different growth speed populations and the process of hypoxia exposure and reoxygenation, respectively. The high-density genetic linkage map and QTLs for growth traits and hypoxia tolerance obtained in the present study could further provide the basis for genetic breeding and molecular marker-assisted breeding of Chinese longsnout catfish.