125 Implementing a Genetic Evaluation Program for Acute Hepatopancreatic Necrosis Disease Resistance in Penaeus Vannamei (Pacific White Shrimp)

Abstract

Abstract This study aims to evaluate the feasibility of a genomic evaluation program for Acute hepatopancreatic necrosis disease (AHPND) resistance in a commercial population of Penaeus vannamei. AHPND is caused by a strain of Vibrio parahaemolyticus (VpAHPND) producing a binary toxin. It is a World Organization for Animal Health (WOAH, Paris, France)-listed bacterial disease that has caused severe economic losses to the shrimp industry worldwide in recent years. The working hypothesis of this study is that the genetic variation in a commercial P. vannamei population allows an efficient genetic and genomic selection program. To investigate the genetic parameters for AHPND resistance, a controlled challenge experiment was performed at the Shrimp Improvement System biosafety laboratory in Miami, Florida, following an immersion challenge protocol using 4.95 × 107 CFU/ mL bacteria and Specific Pathogen Free (SPF) P. vannamei post larvae (n = 2,400) representing 40 selected families. The bioassay was terminated at 3 days post-challenge. Each family consisted of 60 animals, with one-half of the families (n = 20) representing a fast-growth (FG) line and the remaining one-half (n = 20) representing a slow-growth (SG) line. Survival was recorded as a binary of dead or alive at the end of the three days challenge experiment. Variance components were estimated under an animal threshold binary model using a Gibbs sampler. Estimation of genetic parameters was done within lines and by combining all data records. The average hazard risk ratio (HRR) of survival was 80% greater for the FG line (average mortality 40%) than the SG line (average mortality 20%, P < 0.05) based on survival analysis with a 31% mortality rate combining all data records. The posterior mean estimates of heritabilities were 0.14 (± 0.06) for FG, 0.16 (± 0.07) for SG, and 0.38 (± 0.08), combining all records. Estimated breeding values (EBVs) based on the animal threshold binary model ranged from -0.76 to 1.01 on the liability scale. Spearmans’ rank correlation coefficient between the average EBV of parents and the average mortality rates of corresponding families was 0.98. The results suggest that a breeding program for AHPND resistance is feasible. Moreover, the heritabilities suggest that both lines will respond to mass selection due to the presence of additive genetic variation for APHND-survivability. The next step of this project is to genotype animals from every family and implement a genomic selection program. Additionally, high throughput laboratory results and histopathology scores will be introduced in the genetic evaluation as correlated traits.