Evaluation of a commercial SPF Litopenaeus vannamei shrimp breeding program: Resistance to infectious myonecrosis virus (IMNV), Taura syndrome virus (TSV), and white spot syndrome virus (WSSV) from laboratory challenges

Litopenaeus vannamei is the most widely cultured shrimp species in the world and has been impacted by the emergence of various diseases over the course of its history. Infectious myonecrosis virus (IMNV), Taura syndrome virus (TSV), and white spot syndrome virus (WSSV) are three primary pathogens having caused financial losses for shrimp farmers. The purpose of this post hoc study was to evaluate the effectiveness of laboratory viral challenges for resistance to IMNV, TSV, and WSSV for a commercial breeding population of L. vannamei. Phenotypic records for viral challenges from 20 batches, including 442 full-sib families over approximately 2.3 generations were included in the study. Independent challenges for each virus were conducted with late-stage post larvae (PLs) inoculated with viral suspensions. Binary survival data was analyzed with both logistic regression and linear animal models. Heritability estimates were low for the logistic regression models on both the underlying liability scale (0.15 to 0.17) and the observed scale (0.08 to 0.11) for resistance to the three viruses and low (0.23) to moderate (0.39) for the linear animal models for TSV and IMNV, respectively, indicating resistance as defined during challenges is under some level of additive genetic control. Heritability estimates for the linear animal model were not obtained for WSSV resistance due to non-convergence of the model. Estimated breeding values (EBVs) from the logistic regression models were regressed against time, showing significant positive genetic trends, equating to 18.7, 3.0, and 27.4% average genetic gains per generation for IMNV, TSV, and WSSV resistance, respectively. Genetic correlations between viral-resistance traits were weak (0.135 to 0.204), but positive and significant (p < 0.01).