Aquaculture America 2024

February 18 - 21, 2024

San Antonio, Texas

GENOMIC EVALUATION AND GENETIC PARAMETERS FOR ACUTE HEPATOPANCREATIC NECROSIS DISEASE (AHPND) RESISTANCE IN Penaeus vannamei (PACIFIC WHITE SHRIMP): INSIGHTS FROM CONTROLLED CHALLENGE EXPERIMENTS AND POPULATION GENOMICS

Issabelle Ampofo1*, Hung N. Mai2, Arun K. Dhar2, Daniel Grevers3, Harris Wright3, Breno O. Fragomeni1

1University of Connecticut, Storrs, Mansfield CT 06626

 



This study aims to evaluate the feasibility of a genomic evaluation program for Acute hepatopancreatic necrosis disease (AHPND) resistance in a commercial population of P enaeus 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 genomic selection program. To investigate the genetic parameters for AHPND resistance,  two controlled  challenge experiments were performed at the Shrimp Improvement System biosafety laboratory in Miami, Florida . In the first experiment ,  an immersion challenge protocol  was followed where  2400  Specific Pathogen Free (SPF) P. vannamei post larvae from 40 families were challenged with VpAHPND . Each family consisted of 60 animals, with half of the families representing a fast-growth (FG) line and the remaining half representing a slow-growth (SG) line .  The bioassay was terminated at 3 days post-challenge.  In the second experiment , individuals from the best and worst  performing  families (N=20 families each) were selected and challenged with the same bacteria. In both challenges, s urvival was recorded as a binary of dead or alive at the end of the three-day challenge experiment.  In each challenge, 30 animals in each family were kept for a growth control test.  Variance components  and breeding values were estimated under an animal threshold binary model using a Gibbs sampler. Population structure analysis was conducted using data on 1, 024 shrimps  from the control population. Animals  were genotyped on a  commercial shrimp Single Nucleotide Polymorphism (SNP) with 50k markers (Center for Aquaculture Technologies, San Diego, CA).  Estimation of genetic parameters was done within lines and by combining all data records.   In the first challenge,  the FG line mortality was 40%, and the SG line mortality was 20%. The average hazard risk ratio (HRR) of survival was 80% greater for the FG line than the SG line (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.  In the second challenge,  the SG and FG mortality  averaged at 65% and 78%, respectively. T he SG line had a 38% reduced risk of mortality compared to the FG line (P<0.05) with a 71% mortality rate combining all data records. The posterior mean estimates of heritabilities were 0.23(±0.08) for FG, 0.47(±0.13) for SG, and 0.34(±0.06), combining all records. Population structure analysis using  genotyped individuals revealed distinct, non-overlapping ancestry between the two genetic lines. The results suggest that a breeding program for AHPND resistance is feasible. Moreover, the heritabilities suggest that both lines will respond to selection due to the presence of additive genetic variation for APHND-survivability. The next step of this project is to use  the phenotypes and  genomic information  on the challenged animals to implement  a genomic selection program .  Additionally,  high throughput laboratory results and histopathology scores  will be introduced as correlated traits in the genetic evaluation.