Abstract:To breed the Litopenaeus vannamei that could resist low temperature during production cycle, this study investigated the heterosis advantage in breeding program and compareds the growth performance and genetic diversity between two populations under the low temperature conditions. One population, namely the Selected Population (SP), was bred for three consecutive years in our aquatic laboratory, whereas the other one, the Hybrid Population (HP), came from the hybridization of the Selected Population and the Introduced Population. The results showed that the growth performance of HP was significantly higher than SP. The average body weight of HP and SP shrimps were (13.18±3.65) g and (12.20±3.14) g respectively, and the coefficient of variation were 27.69% and 25.74%, respectively. The average body weight and other measurable traits in HP were higher than those in SP. The results of One-way ANOVA indicated that there were significant differences (P<0.001) between HP and SP in both body weight and TASW. The specific growth rate (SGR) and absolute growth rate (AGR) in HP were (5.09±0.61) %/d and (0.26±0.60) g/d, respectively. By comparison, in SP group, the SGR was (4.94±0.57) %/d and the AGR was (0.24±0.63) g/d, significantly lower (P<0.01) than the HP group. The results of genetic diversity analysis showed that the Na of HP (Na=7.9) was slightly higher than SP (Na=7.6). The average polymorphic information content (PIC) of HP and SP was similar as 0.63 and 0.62, respectively, both belong to the relatively high polymorphism level. The average observed heterozygosity (Ho) of HP and SP was 0.492 and 0.483, respectively, and the expected heterozygosity (He) was 0.675 and 0.663, respectively. Both Ho and He in HP were higher than that in SP, suggesting that HP had higher genetic diversity abundant compared to the SP. The analysis of genetic differentiation indicated that the genetic differentiation was significant between HP and SP, with the genetic differentiation index (Fst) between HP and SP was 0.1556. The results of this study provides a genetic background and production experience of L. vannamei for breeding low temperature breed and crossbreeding technique.
