Selective breeding applied to aquaculture is a strategic research area for Brazil, in view the unavailability of genetically improved native species. This study aims to characterize genetically pacu (Piaractus mesopotamicus) resistant to the Aeromonas hydrophila bacteria. The specific objectives are: 1) characterization of immune system genes, by RNA-seq technique, of susceptible and resistant individuals challenged with A. hydrophila infection; 2) characterization of QTL (Quantitative Trait Locus) associated with resistance to A. hydrophila, by sequencing / genotyping of SNPs (ddRAD-seq, double-digest restriction- site-associated DNA sequencing). In relation to RNA-seq experiment, after inoculation of A. hydrophila, analyses will be performed at the following times: T1 (early death of animals), fishes that show signs of infection, considered susceptibles; T2 (after mortality plateau), individuals considered resistant to A. hydrophila challenge; and both T1 and T2, control treatment individuals inoculated with saline solution. Bioinformatic analyses will be performed from de novo assembly of pacu transcriptome, comparing T1 x Control, T2 x Control and T1 x T2. Afterwards, sequencing / genotyping will be performed by ddRAD-seq technique (restriction enzymes SphI and MluCI), in order to realize molecular analysis of 10 pacu families challenged with A. hydrophila, which will allow the search for QTL and provide support for marker-assisted selection. The potential impact of this study is to make feasible technologies for production of improved fishes for the aquaculture industry.
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