Haplotypes traceability and genetic variability of the breeding population of pacu (Piaractus mesopotamicus) revealed by mitochondrial DNA.

Milena V De Freitas,Milene E Hata,Diogo T Hashimoto,Gabriela V Villanova,Felipe Del Pazo,Fernando F Mendonça,Raquel B Ariede,Fábio Porto-Foresti,Vito A Mastrochirico-Filho

doi:10.1590/1678-4685-gmb-2020-0249

Abstract

The main objective of this study was to estimate the genetic diversity levels and haplotype traceability in pacu Piaractus mesopotamicus from the breeding program located in Brazil by analyses of the mitochondrial DNA control region (mtDNA). Moreover, broodstocks from eight commercial fish farms were used for comparative evaluation, four from Brazil (Br1-Br4) and four from Argentina (Ar1-Ar4). The descriptive results revealed 47 polymorphic sites and 51 mutations, which evidenced 34 haplotypes. Ten haplotypes were shared among fish farms and 24 were exclusive. The nucleotide diversity (π) ranged from 0.00031 to 0.01462 and haplotype diversity (Hd) from 0.125 to 0.868. The analysis of molecular variance (AMOVA) indicated high structure present in the analyzed stocks (F ST = 0.13356 and ФST = 0.52707). The genetic diversity was high in most of the commercial broodstocks, especially those from Brazil. We observed seven haplotypes in the genetic breeding population, of which four were exclusive and three shared among the commercial fish farms. The genetic diversity was moderate (π = 0.00265 and Hd = 0.424) and considered appropriated for this breeding population of pacu. Our results provide support for the genetic diversity maintenance and mtDNA traceability of pacu commercial broodstocks.

Highlights

The species Piaractus mesopotamicus, popularly known as pacu, is a Serrasalmidae fish of commercial importance distributed in the Paraná, Paraguay, and Uruguay River basins, mainly in the Pantanal plains (Petrere Jr, 1989)
The main objectives of this study were: 1) to assess the genetic diversity by mitochondrial DNA control region (mtDNA) in the breeding population of pacu from Caunesp (Aquaculture Center of the São Paulo State University, Brazil); 2) to identify unique haplotypes in this breeding population for traceability of products resultant from genetic improvement by mtDNA; 3) to compare farmed stocks from different Brazilian and Argentinian commercial fish farms by mtDNA in order to detect non-contemporary genetic differences of founder stocks and to understand the haplotype diversity and distribution between these countries
The main genetic problems arising from the inappropriate use of fish in breeding programs can be reduced and even avoided using the genetic profile of the individuals and proper genetic management practices, as it was performed to compose the base population of the breeding nucleus (CAUNESP) in pacu (Mastrochirico-Filho et al, 2019b; Freitas et al, 2020)

Summary

Introduction

The species Piaractus mesopotamicus, popularly known as pacu, is a Serrasalmidae fish of commercial importance distributed in the Paraná, Paraguay, and Uruguay River basins, mainly in the Pantanal plains (Petrere Jr, 1989). Pacu is one of the main farmed fish of the South American aquaculture, occupying the 6th position of production in Brazil, together with its hybrid patinga (obtained by crossing P. mesopotamicus and Piaractus brachypomus), with an estimated annual production of 13,276 tons (IBGE, 2015). The formation of inbred families and the use of breeding units with low genetic variability result in loss of genetic potential and inbreeding risks (Melo et al, 2006; Charlesworth and Willis, 2009). The characterization of genetic variability is a fundamental tool when initiating genetic breeding programs (Mastrochirico-Filho et al, 2019a), few studies have been developed in this scope

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