Genetic additive variance for IHHNV susceptibility and prevalence, and its genetic relationship with growth and survival traits in Pacific white shrimp (Penaeus vannamei) from Ecuador's PMG-BIOGEMAR® breeding program

In the industrial farming of P. vannamei, disease is a major cause of economic loss, and infectious hypodermal and hematopoietic necrosis virus (IHHNV) is one of the diseases of P. vannamei that affects many populations worldwide. This study aimed to estimate the heritability and genetic correlations of the following traits: IHHNV diagnostic parameters (IHHNV threshold cycle [Ct] values, copy number [viral load] by quantitative PCR [qPCR, TaqMan probes], and survival) from naturally infected animals, growth (weight, length, and condition factor), and morphology (cephalothorax length and first segment width) in P. vannamei from the PMG-BIOGEMAR (R) breeding program for growth under industrial production conditions in Ecuador. A total of 11,457 shrimp from 120 full-sibling families were reared in an intensive culturing system (tank) (BIOGEMAR, San Pablo, Ecuador) and evaluated for genetic parameters at harvest size. Low-medium (0.12-0.30) heritability was found for growth and morphological traits, as well as for IHHNV Ct values, copy number, and survival (0.01-0.18). The genetic correlation between weight and IHHNV Ct values and copy number was very low (0.01 and 0.05, respectively), and low for weight and survival (0.29). Furthermore, the genetic correlation between IHHNV copy number and survival was low and negative (-0.35), indicating that genetic selection for weight does not affect survival or susceptibility to IHHNV infection and that IHHNV infection does not affect survival in the population from the PMG-BIOGEMAR (R) breeding program of the Ecuadorian industrial sector.