Análise genética na investigação de origem da tilápia (Oreochromis niloticus) em cultivos comerciais

Abstract

The development of genetically improved tilapia strains was an important step in world aquaculture, considering growth, reproduction, weight gain, fillet yield and greater rusticity of the selected individuals. Acquiring improved seeds is the first step to shortening production time, however, the fish farmer should provide adequate conditions and structure to achieve optimal maximum performance. In biphasic tilapiculture systems in excavated nurseries, it is common for the nursery phase to occur in a different location than the fattening phase. In this case study, one producer purchased improved fingerlings from a tilapia breeding company “A” and sent them to company “B” to conduct the nursery phase. However, when such the producer received the “B” tilapia juveniles and fattened them, they did not show the expected zootechnical performance. The objective of this study was to detect if the tilapia of "A" and "B" had the same genetic origin. Were used genetic markers such as microsatellites and mitochondrial DNA control region (D-loop). A total of 79 samples were collected, of which 40 were from “A” and 39 from “B”. The samples had their total DNA extracted and were genotyped for the UNH104, UNH106, UNH160 and UNH208 microsatellite markers. Then, the samples had the control region haplotypes identified by sequencing. The genetic diversity of microsatellites was analyzed to correctly attribute that the origin of "B" came from "A". The alignment and editing of the D-loop also revealed a haplotype network with equitable stakes of "A" and "B" confirming that the groups belonged to the GIFT lineage. The techniques used show that the different zootechnical performance should be associated with issues related to the adopted management and stocking density during the nursery phase.