Introgressive crossbreeding between Red-Stirling and Chitralada tilapia was carried out to assess the association of STR loci polymorphisms located in the growth hormone (GH1) promoter and intron-I with growth performance. The growth of seven genetic groups was assessed using a mixed linear model. We considered sex, age, and initial weight class of each animal as fixed effects, while genetic group, STR-promoter, and STR-intron were considered as random effects. We found six alleles in the STR-promoter, which were arranged in 18 of the 21 genotypic possible combinations. Alleles 191 and 196 of the STR-promoter correspond to 80% of the assessed individuals’ total alleles, and genotypes 196/196, 191/196, and 196/201 were the most frequent. We found only three alleles in the STR-intron. The loci STR-promoter showed a significant association with the animals’ weight. Genotypes 181/181, 181/191, and 196/206 showed better average performance, and genotypes 196/201, 201/201, and 191/196 showed the worst performance. The polymorphism in the STR-intron was not associated with fish weight. The proposed approach is unprecedented for STR found in the GH1 gene. The observed association indicates that GH1 gene polymorphism could be used as a tool in tilapia breeding programs.

Introgressive crossbreeding between Red-Stirling and Chitralada tilapia was carried out to assess the association of STR loci polymorphisms located in the growth hormone (GH1) promoter and intron-I with growth performance. The growth of seven genetic groups was assessed using a mixed linear model. We considered sex, age, and initial weight class of each animal as fixed effects, while genetic group, STR-promoter, and STR-intron were considered as random effects. We found six alleles in the STR-promoter, which were arranged in 18 of the 21 genotypic possible combinations. Alleles 191 and 196 of the STRpromoter correspond to 80% of the assessed individuals' total alleles, and genotypes 196/196, 191/196, and 196/201 were the most frequent. We found only three alleles in the STR-intron. The loci STR-promoter showed a significant association with the animals' weight. Genotypes 181/181, 181/191, and 196/206 showed better average performance, and genotypes 196/201, 201/201, and 191/196 showed the worst performance. The polymorphism in the STR-intron was not associated with fish weight. The proposed approach is unprecedented for STR found in the GH1 gene. The observed association indicates that GH1 gene polymorphism could be used as a tool in tilapia breeding programs.PeerJ Preprints | https://doi.org/10.7287/peerj.preprints.26592v1 | CC BY 4.0 Open Access | rec: