Aeromonas hydrophila is a gram-negative bacterium considered a harmful pathogen to human health and to fish from freshwater environments. In Brazil, aeromoniosis causes high mortality rates in several fish species, including tambaqui (Colossoma macropomum). This study aims to perform a genome-wide association study for resistance to A. hydrophila in tambaqui. The specific objectives are: 1) to develop a dense linkage map using data from ddRAD-seq (double-digest restriction site associated DNA sequencing) in tambaqui; 2) to characterize genomic regions of QTL (quantitative trait locus) associated with resistance to A. hydrophila in tambaqui. Sequencing/genotyping by ddRAD-seq will be characterized in 18 families of tambaqui challenged with A. hydrophila, which will allow assessing thousands of SNPs (single nucleotide polymorphisms). The traits evaluated for disease resistance will be survival rate and time of death. Initially, a medium density linkage map (~15K SNPs) will be constructed for tambaqui, which will serve for downstream analyses of genomic association. Next, statistical models for SNP/traits association will be applied to perform genome-wide association study and to detect QTL. SNPs that have significant association will be functionally annotated by comparisons with genomes of nearby species. The expected result is to generate a significant advance for breeding studies on native fish, particularly for a better understanding of genomic regions associated with disease resistance traits. The potential impact of this study is to make viable technologies for the production of improved fish for the aquaculture industry.
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