GENETIC ANALYSIS OF FARM STOCKS FOR PACÚ (PIARACTUS MESOPOTAMICUS) AQUACULTURE, A GROWING ACTIVITY IN THE REGION.

DEL PAZO F.; VIEIRA DE FREITAS M.; SCIARA, ANDRÉS A.; HASHIMOTO D.T.; ARRANZ S.E.; VILLANOVA, G.VANINA

Cairns

Simposio; ISGA XIII International Symposium of Genetics in Aquaculture; 2018

International Association for Genetics in Aquaculture (IAGA)

The pacú, Piaractus mesopotamicus, is a neotropical fish widely distributed in the Plata basin and its aquaculture is successfully carried out in Argentina and Brazil. In Argentina it is the main product of aquaculture, and in Brazil it reaches the sixth place in production value. However,  breeding programs have not been started and production is based on breeders without pedigree records. In this work, genetic diversity and population structure of 7 breeding populations of Brazil and 8 of Argentina was analysed using 8 microsatellite markers. A reference wild population was included for comparison. High levels of polymorphism were observed at microsatellite loci in both wild and farm populations. The number of alleles varied from 42 to 16, the expected and observed heterozygosity values ​​ranged between 0.423-0.596 and 0.379-0.572 respectively, and allelic richness varied between 2 and 3.74. Private alleles were found in wild population, as well as in five farms. Although the highest values ​​in diversity parameters were found for wild population, no significant differences were observed in the observed (Ho) and expected (He) heterozygosity between the  farms and wild population (P<0.00625). In addition, similar degrees of inbreeding were detected. Departures from the Hardy-Weinberg equilibrium were observed in farms, caused by both deficits and excesses of heterozygotes. Bottleneck test showed a reduction in the population size in one of the fish farms.Genetic variation was found among different farms populations through AMOVA analysis. Pairwise FST values ​​indicated on average, a moderate and significant genetic differentiation (Global FST=0.095). Two farms populations presented higher FST values that suggested high levels of genetic differentiation. Dendrogram and FCA supported this result. The same two farms showed the highest percentage of related individuals using the TrioML Rxy estimator. Structure analysis  revealed three genetic groups (k=3) homogeneously distributed in all the populations, which suggested absence of genetic structure. These results provide useful information for the genetic monitoring of aquaculture populations of P. mesopotamicus, for future genetic improvement programme and selective breeding.