Diversidade genética de três linhagens de tilápia do Nilo (Oreochromis niloticus) submetidas à seleção massal

Abstract

Reproductive management practices carried out in the aquaculture production systems may inadvertently decrease the genetic variability of populations due to the use of small groups of players. This characteristic of this type of system can lead to an increase in inbreeding and consequently a significant decrease in the growth and affect other factors of interest. All these factors can negatively affect the system and jeopardize its sustainability. The objective of this research was to analyze the genetic diversity through microsatellite markers from three strains of Nile tilapia in two generations undergoing mass selection. The locus were used: UNH160, UNH178, UNH222, ISPMS01, PRMS01 and PRMS02. From these loci were obtained, number of alleles, observed and expected heterozygosity, the test of Hardy- Weinberg equilibrium, the coefficient of inbreeding and population differentiation, genetic diversity and allele frequencies. The average number of alleles per locus in each pedigree showed no loss of alleles between one and the next generation evidencing that the mass selection had no negative effect on the number of alleles. High indices of inbreeding were observed in the initial and filial generation of strains under study, demonstrating the importance of analysis provided the initial populations. The coefficient of population differentiation of strains identified homogenization throughout the processes of selection and these little variation with respect to their future generations, indicating nonexistent effects of mass selection on allele frequencies. The study results showed no negative effects of mass selection on genetic diversity in the three tilapia strains studied in the initial generation and affiliate.