Prospects for Genetic Improvement in Objective Measurements of Body Colour in Pacific Whiteleg Shrimp (Litopenaeus vannamei)

Body colour, together with growth and survival, are traits of commercial importance in Pacific whiteleg shrimp (Litopenaeus vannamei). However, heritability estimates for objective measurements of body colour are not available in Whiteleg shrimp species, including L. vannamei. Further, the effect of genotype by environment interactions (G × E) on this trait (i.e., the objective measures of body colour) and its genetic associations with growth are not known in this species. The present study presented the first attempt at understanding the genetic architecture of this complex character (body colour) that is of economic significance to the shrimp aquaculture sector world-wide. Specifically, we investigated the quantitative genetic basis of shrimp colour, while using the measurement tool (colorimeter) for a Whiteleg shrimp population reared in two contrasting environments. A total of 5464 shrimp had the objective measurements of body colour (lightness, yellowness, and redness) and growth trait records (weight, length and width). They were the offspring of 204 dams and 197 sires. The restricted maximum likelihood mixed model analysis showed that there were heritable additive genetic components for all of the measurements of shrimp colour, with the heritability (h2) ranging from 0.11–0.55. The h2 estimates for redness and yellowness traits differed between the two environments (h2 = 0.66–0.82 in Khanhhoa vs. 0.00–0.03 in Haiphong). However, the heritability for colour traits was moderate (0.11–0.55) when the two environments were combined. There is existence of (co)-genetic variances between the studied traits. The genetic correlations of body traits with redness or yellowness colour of the shrimp were moderate and positive (a*: 0.13–0.32 for redness and b*: 0.19–0.40 for yellowness). The effect of G × E interactions on shrimp colours could be important, as the genetic correlations for these traits between the two environments were low (−0.41 to 0.16). Our results showed that the genetic improvement for body colour can be achieved through direct selection and the increased redness colour is also expected to have favorable impacts on growth traits. Breeding programs to improve shrimp colour should account for the effects of environmental factors.