Interactive effects of genotype x environment on the live weight of GIFT Nile tilapias

ABSTRACT In this paper, the existence of a genotype x environment interaction for the average daily weight in GIFT Nile tilapia (Oreochromis niloticus) in different regions in the state of Paraná (Brazil) was analyzed. The heritability results were high in the uni-characteristic analysis: 0.71, 0.72 and 0.67 for the cities of Palotina (PL), Floriano (FL) and Diamond North (DN), respectively. Genetic correlations estimated in bivariate analyzes were weak with values between 0.12 for PL-FL, 0.06 for PL and 0.23 for DN-FL-DN. The Spearman correlation values were low, which indicated a change in ranking in the selection of animals in different environments in the study. There was heterogeneity in the phenotypic variance among the three regions and heterogeneity in the residual variance between PL and DN. The direct genetic gain was greater for the region with a DN value gain of 198.24 g/generation, followed by FL (98.73 g/generation) and finally PL (98.73 g/generation). The indirect genetic gains were lower than 0.37 and greater than 0.02 g/generation. The evidence of the genotype x environment interaction was verified, which indicated the phenotypic heterogeneity of the variances among the three regions, weak genetic correlation and modified rankings in the different environments.摘要 本研究针对巴西巴拉那州不同养殖区域的吉富品系尼罗罗非鱼（GIFT Nile tilapia，*Oreochromis niloticus*）的平均日增重开展基因型-环境互作（genotype × environment interaction）分析。单性状分析所得遗传力数值较高：帕洛蒂纳（Palotina, PL）、弗洛里亚诺（Floriano, FL）和北钻石（Diamond North, DN）三地分别为0.71、0.72和0.67。双性状分析估算的遗传相关较弱，PL与FL间为0.12、PL与DN间为0.06、DN与FL间为0.23。斯皮尔曼相关系数数值偏低，表明本研究不同环境下的选育动物排名发生改变。三地的表型方差存在异质性，PL与DN间的残差方差亦存在异质性。直接遗传增益以DN区域最高，每世代可提升198.24 g，其次为FL（98.73 g/世代）与PL（98.73 g/世代）。间接遗传增益介于0.02~0.37 g/世代之间。本研究验证了基因型-环境互作的存在，具体表现为三地间方差的表型异质性、较弱的遗传相关以及不同环境下的选育排名改变。