The Selective Breeding Research On The Growth, Reproduction And High Ammonia Nitrogen Tolerance In Litopenaeus Vannamei

Pacific white shrimp, Litopenaeus vannamei, has become the Chinese largest of farming area and highest yield shrimp species in recent years. But, this broodstocks of the shrimp for china need to introduce alien germplasm from aboard company, such as CP(Charoen Pokphand Group), SIS(Shrimp Improvement Systems) and Kona Bay Marine Resource, germplasm bred by china lack of competitiveness. Breeding the high quality germplasm of this shrimp with good growth performance, reproductive and environment factor tolerance, is a useful way to developing the competitiveness. Therefore, the selective breeding research for development the growth performance, reproductive and environment factors tolerance is being carried out, which was through the introduction good germplasm form domestic and foreign, and combing group breeding, cross breeding and pedigree breeding. The main research is as follows:1. A comparative study of hypoxia and high-ammonia resistance among Litopenaeus vannamei inbred and hybrid offspring at different stages at G1We conducted a comparative study of hypoxia and high-ammonia resistance in Litopenaeus vannamei after 48 hours of stress in different mating combinations of the G1 generation at the juvenile and adult stages. We set up eight mating combinations of inbred and hybrid L. vannamei with six different genetic backgrounds. The results show that the difference between different mating combination in the same growth stage for hypoxia and high-ammonia resistance are significant, selecting 3 mating combinations as candidates for hypoxia-resistant breeding and selecting 4 mating combinations as candidates for ammonia-resistant breeding. Hypoxia and high ammonia resistance of the HD♀× YH♂mating combination was high, but the correlation between hypoxia and high-ammonia resistance in the different mating combinations was not significant. We found that if a female parent originated from the YH group, its offspring were also hypoxia resistant,suggesting that the hypoxia resistance trait is a maternal dominant genetic trait. Hypoxic resistance decreased during the growth and development of the shrimp. The correlation between mating combinations of juvenile and adult shrimp for hypoxic stress and high-ammonia stress was highly significant(P < 0.01). These results suggest that the hypoxia and high-ammonia resistance traits of L. vannamei should be evaluated at the juvenile stage.2. Genetic parameters for growth-related traits and survival in Pacific White Shrimp,Litopenaeus vannamei at G2 under conditions of high ammonia-N concentrationsIn this experiment, set up 40 whole families by 8 mating combinations in G1 with avoiding inbreeding mating. Estimates of the genetic parameters in Litopenaeus vannamei for growth-related traits(body weight, body length, abdominal segment length, carapace length) at 7 and 14 weeks of age and examined survival at 96 hours under conditions of high ammonia-N concentrations during each growth stage. The heritability estimates for growth-related traits at different growth stages were moderate, ranging from 0.24 to 0.30 at7 weeks and 0.26 to 0.31 at 14 weeks, respectively. The heritability estimates for survival under conditions of high ammonia-N concentrations were 0.13(P>0.05) at 14 weeks and0.17 at 21 weeks, respectively. Genetic correlations between growth-related traits within age cohorts were generally high(ranging from 0.74 to 0.89); genetic correlations between body weight and survival under conditions of high ammonia-N concentrations were0.31±0.11,(P<0.05). Our results suggest that selection to improve any single body trait would likely produce correlated responses in the other traits examined and that selecting for growth will cause a positive correlated response in terms of survival under conditions of high ammonia-N concentrations.3. A comparative study of reproductive traits among different Litopenaeus vannamei families at G2We conducted a comparative study of reproductive traits of 15 Litopenaeus vannamei seed families in G2 for 60 days, and analysis the correlation between each reproductive trait. The results show that the fecundity of F413 was most(265.2 thousand). The shortest intervals of spawning consecutive families were F407 and F401, respectively with5.03 days and 5.07 days. The correlation coefficient between spawning weight and fecundity, between fecundity and fertilization rate and between fecundity and hatch rate,respectively were 0.260, 0.155 and 0.239, which were all high significant correlated(P<0.01). However, the correlation coefficient between spawning consecutive and hatching rate and between interval of spawning consecutive and fecundity respectively were-0.121 with significant correlated(P<0.05) and-0.078 with high significant correlated(P<0.01).Studies have shown that L.vannamei females reproductive performance with a larger family selection potential and the fecundity and intervals of spawning consecutive should be the goal traits for high reproductive L.vannamer stain breeding.4. Estimates of heritability and response for growth related traits and high ammonia tolerance in Litopenaeus vannamei families at G3The establishment of 20 half-sib families and 75 full-sib families by 15 the G2 seed families with avoiding inbreeding, which was selected by index selection. Estimates of the genetic parameters in Litopenaeus vannamei for growth-related traits(body weight, body length, abdominal segment length, carapace length) at 14 weeks of age and examined survival at 96 hours under conditions of high ammonia-N concentrations. The heritability estimates for growth-related traits at different growth stages were moderate, ranging from0.216 to 0.284 at 14 weeks a. The heritability estimates for survival under conditions of high ammonia-N concentrations was 0.028±0.026(P>0.05). Genetic correlations between growth-related traits within age cohorts were generally high(ranging from 0.841 to 0.948);genetic correlations between body weight and survival under conditions of high ammonia-N concentrations were 0.18 ± 0.032,(P<0.05). The response for body weight were ranged from 0.542 to1.039. The response of survival under conditions of high ammonia-N concentrations were ranged from 0.028 to 0.046. The results showed that the growth related traits was improved significant at G3, but high ammonia tolerance made small genetic progress.5. The effect of different inbreeding families at G3 degree on the growth related traits,survival, hypoxia and high-ammonia toleranceThe establishment of 4 highly inbred families, 4 moderately inbred families and 4non-inbred pedigree by the G2 seed family. We conducted a comparative study of the growth related traits, survival, hypoxia and high-ammonia tolerance among different inbred families. The results showed that the body weight of 75% inbred families expressed inbreeding depressing, but a moderately inbred family Z2 have a heaviest body weight than non-inbred group body weight. all non-inbred families.The body weight of highly inbred group was significant less than non-inbred group group,s(P>0.05).The survival of 50%inbred families expressed inbreeding depressing, but a highly inbred family G3 have a highest survival than all non-inbred families. The hypoxia of 62.5% inbred families expressed inbreeding depressing.Those suggested that inbreed depressing is prevalence in breeding, but rational use of inbred also can speed up the process of genetic improvement.