Comparisons and genetic assessments of WSSV resistance and growth in strain cross of Litopenaeus vannamei

Abstract

To explore the performance differences among offspring obtained by the intra- and inter-strain crosses, strain A with outstanding WSSV resistance and strain B with outstanding growth of Litopenaeus vannamei were used to construct four experimental groups in a complete diallel cross. 27 growth-related phenotypic traits and WSSV resistance represented by the surviving hours post-infection were obtained via the growth and the virus challenge test. Mixed linear model along with physical pedigree were utilized to calculate the least squares means, correlations, heritability and heterosis. The results showed that crossbreeding can realize character complementation of advantage strain. The performance of WSSV resistance was ranked AA> BA> AB> BB, and the reciprocal crosses performed significantly better than intra-strain group BB. Most growth-related traits in two reciprocal cross groups were also significantly better than those in AA group. Comparisons between the two reciprocal crosses showed that BA cross was better than AB in terms of WSSV resistance and growth. Heterosis of WSSV resistance in BA cross was 5.74∼10.18% greater than that in AB, meanwhile the absolute weight gain rate of BA cross was 4.83% higher than that of AB. The heritability estimates of body length and body weight were 0.0278 and 0.339, both of which reached medium level. The genetic and phenotypic correlations among growth-related traits were from 0.36 to 0.99 and 0.32 to 0.99, respectively. In term of WSSV resistance, the heritability estimate was 0.135 ± 0.082. The genetic and phenotypic correlations between WSSV resistance and growth-related traits were from − 0.034 to − 0.573 and − 0.001 to − 0.202, respectively. The results showed that hybrid offspring obtained by crossing female parents with outstanding WSSV resistance and male parents with outstanding growth culminated in a superior heterosis in both traits. This study provides basic reference data for L. vannamei breeding of new strains that are disease resistant and fast-growing.