Molecular genetic approaches to the study of fish resistance to diseases

The purpose of the review is to summarize current information about viral, bacterial and parasitic fish diseases, for which molecular markers are currently being investigated for resistance. The advantages of conducting experimental studies on individuals included in genome-wide associative studies in combination with a comparative analysis of immune genes expression in affected fish, affected asymptomatic and control fish that do not exposed to the pathogen. Methods used: comparative analysis of modern literature data, deconstruction method: careful selecting studies that reflect the main points of the data on the immune response of fish studied to date. The review results in structured data on studies of the immune response of fish to various pathogens. Importance: aquaculture is facing an increasing number of pathogenic microorganisms affecting cultivated fish from year to year. The fishing industry needs more efficient and faster breeding methods. Traditional breeding approaches aimed at increasing the natural resistance of fish to diseases require decades, which is associated with a long time to reach sexual maturity of fish. The use of genome-wide association studies (GWAS), as well as the registration of markers such as microsatellites and single nucleotide polymorphisms (SNPs), allows for selection using marker methods. Research shows that these technical approaches can identify quantitative trait loci (QTL) and identify individuals with high natural resistance to diseases. Comparative analysis of SNPs in surviving and dead fish makes it possible to detect specific genetic markers associated with resistance and accurately determine their location in the genome. The data obtained are the basis for the selection of parental genotyped individuals for breeding generations of fish with increased resistance in a relatively short time.