Insights into isogenic clonal fish line development using high-throughput sequencing technologies

Isogenic clonal fish lines are a powerful resource for aquaculture-related research. Fully inbred individuals, clone founders, can be produced either through mitotic gynogenesis or androgenesis and a further generation from those propagates fully inbred clonal lines. Despite rapid generation, as opposed to successive generation of sibling mating as in mice, the production of such lines may be hampered due to (i) potential residual contribution from irradiated gametes associated with poorly optimised protocols, (ii) reduced survival of clone founders and (iii) spontaneous arisal of meiotic gynogenetics with varying degree of heterozygosity, contaminating fully homozygous progenies. This research set out to address challenges and gain insights into isogenic clonal fish lines development by using double-digest RADseq (ddRADseq) to generate large numbers of genetic markers covering the genome of interest. Analysis of potential contribution from irradiated sperm indicated successful uniparental inheritance in meiotic and mitotic gynogenetics European seabass. Exclusive transmission of maternal alleles was detected in G1 progeny of Atlantic salmon (with a duplicated genome), while G2 progenies presented varying levels of sire contribution suggesting sub-optimal UV irradiation which was undetected previously with 27 microsatellite markers. Identification of telomeric markers in European seabass, with higher recombination frequencies for efficient differentiation of meiotic and mitotic gynogenetics was successful, and a genetic linkage map was generated from this data. One clear case of a spontaneous meiotic gynogenetic fish was detected among 18 putative DH fish in European seabass, despite earlier screening for isogenicity using 11 microsatellite markers. An unidentified larval DNA restriction digestion inhibition mechanism observed in Nile tilapia prevented the construction of SNP-based genetic linkage map. In summary, this study provides strong evidence on efficacy of NGS technologies for the development and verification of isogenic clonal fish lines. Reliable establishment of isogenic clonal fish lines is critical for their utility as a research tool.