GENETIC DIVERSITY ASSOCIATED WITH MICROSATELLITE MARKERS IN GROWTH HORMONE GENE AND NEUTRAL LOCI OF THE NILE TILAPIA (Oreochromis niloticus)

DIAS, M.A.D.; DE FREITAS, R. T. F. .; ARRANZ, S.E.; VILLANOVA, G.V.; HILSDORF, A.W.S.

Santiago de Compostela

Simposio; INTERNATIONAL SYMPOSIUM ON GENETICS IN AQUACULTURE XII; 2015

ISGA

Understand the genetic basis of variation in traits related to growth in Oreochromis niloticus is important to the aquaculture industry. The Growth Hormone gene is considered a highly conserved and crucial growth-regulating gene in species and strains of Nile tilapia found worldwide. To successfully use them in breeding programs, they first need to be genetically characterized. In this study, regions on GH1 gene of O.niloticus were genotyped, aligned and compared across four strains (UFLA, GIFT, Chitralada and Red-Stirling). Two microsatellites (STR) were identified in the putative promoter (position -693 / -679, called STR-Promoter, motif (ATTCT) 8) and intron 1 (position +140/+168, called STR-Intron, motif (CTGT)7) regions. The strains were genetically characterized using 10 noncoding microsatellite loci (UNH828, UNH829, UNH009, UNH005, UNH103, UNH104, UNH123, UNH203, UNH866, and GM672) and two microsatellites located in the promoter and first intron of the GH1. The STR-Promoter (6 alleles) and STR-Intron (3 alleles) loci were polymorphic in the four studied strains. A total of 88 alleles with high polymorphism among the studied strains were identified by analysis of 10 noncoding STR loci, except for the UNH-005 locus (with allele 159, private in UFLA and GIFT strains) and the UNH-866 locus (with allele 167, private in the Red-Stirling strain, and with alleles 171 and 177, private in the UFLA and Chitralada strains, respectively). Genetic diversity was measured as mean expected heterozygosity and numbers of alleles, which were 4 and 0.60 (GIFT), 3.5 and 0.71 (UFLA), 4.5 and 0.57 (Chitralada), and 2.5 and 0.42 (Red-Stirling), respectively. The UFLA and GIFT strains are less genetically divergent (DEST = 0.10) and have similar structure in relation to Chitralada and Red-Stirling strains (DEST = 0.32 and 0.33; 0.45 and 0.47, respectively), with the latter being the most distant (DEST = 0.59). UFLA strain was genetically characterized and presented as an important source of variability adapted to regions with mild temperatures. Validation and association studies with performance char¬acteristics of STR-Promoter and STR-Intron loci should be performed to confirm the poten¬tial of these loci as possible quantitative trait locus on marker-assisted selection programs.