| Litopenaeus vannamei is one of the important marine shrimp species in China.After solving the problem of artificial breeding,it has become the major species in the shrimp culture industry in China,and it is one of the main aquatic products to earn foreign exchange and increase farmers’income.The culture technology of L.vannamei in China is becoming more and more mature and popularized inland,the culture model also tends to be diversified,however,in recent years,there are some germplasm degradation phenomena such as slow growth,low desalination survival rate and frequent diseases in freshwater aquaculture,and the benefit of freshwater culture is seriously damaged.L.vannamei(Xinghai No.1)is a national instance variety that is led by our school,and is currently undergoing subsequent breeding and promotion.There are abundant resources of high salt water area in the north of China,so the high salt environment culture of L.vannamei has great promotion potential.Therefore,the cultivation of a new strain of L.vannamei which are resistant to high salt stress can not only promote the development of high salt shrimp,but also has reaching significance in alleviating the depletion of fresh water resources and new variety promotion.At the same time,in view of the current diversified culture environment,exploring the G×E effect and growth pattern of Litopenaeus vannamei in multi-environment can provide theoretical support for the popularization and culture demonstration of parent shrimp in China.The main results are as follows:(1)Analysis of combining ability and heterosis on growth and high salt tolerance traits of different Litopenaeus vannamei populationsIn this study,we bred ten inbred populations and hybridized F1 population for L.vannamei"Xinghai No.1"population(XH),Thai breeding strain population(D、Z)and American population(S、P)by incomplete diallel cross.After 60 days of culture in the same environment,the growth measurement and high salt stress experiment were carried out,and then evaluated the general combining ability(GCA)and specific combining ability(SCA)in growth and high salt tolerance traits with mixed and generalized linear models.The results showed that the general combining ability effect value was small in the growth traits of the five strains,and the growth traits were mainly affected by the special combining ability under the experimental environment.For high salt tolerance traits,the general combining ability effect values of American strains(P、S)were higher,which were 0.83 and 0.53,respectively.The analysis of special combining ability showed that the self-crossing combination Z♂×Z♀growth character SCA effect value was the largest,which was the optimal combination for growth character.The hybrid P♂×XH has the highest special combining ability for high salt tolerance traits,which is the best combination for high salt tolerance traits and can be used as a candidate material for further family breeding.P♂×XH♀combination has obvious heterosis in growth And high salt tolerance traits,therefore,ought to strengthen the selection and breeding in this group.(2)Estimation of genetic parameters for growth-related traits and resistance to high salt in Litopenaeus vannameiIn this experiment,50 full-sib families were constructed with 6 core breeding populations and 4 introduced populations as parents.After all the shrimp were cultured in the common environment for 60 days,the high salinity stress experiment was carried out,the growth traits were measured,and the genetic parameters of growth and high salt resistance of the selected population of L.vannamei were estimated.The results showed that the heritability of high salt tolerance of L.vannamei was 0.032±0.031,which was not significant,and the heritability of growth-related traits was 0.194-0.242(P<0.01).The genetic correlation and phenotypic correlation among different growth traits showed significant positive correlation(P<0.05),and the genetic correlation between growth traits and high salt tolerance traits was0.072-0.141,showing a low linear positive correlation.(3)Heritability and genotype by environment interactions for growth in Litopenaeus vannamei at indoor and outdoor cultureIn this experiment,using 50 families established in experiment two were carried out in indoor cement pools and outdoor ponds to analyze G×E effects of growth traits.The heredities of the two test groups were 0.155 to 0.190 and 0.180 to 0.220,respectively,all of which were medium genetic powers(P<0.05),and the genetic powers of the growth traits of the outdoor group were higher than the indoor group.The environment is used as a fixed effect,and the heritage of the growth traits is comprehensively assessing between 0.098±0.031 to 0.122±0.032,which is a low heritage level(h~2<0.15).The genetic correlation between the two test groups was(-0.012±0.187)～(-0.067±0.185)was less than 0.8,and the test was not significant(P>0.05).The correlation coefficient of each family of domestic growth is substantially 0,indicating a significant reorder effect.The top 30 offspring in the rank of comprehensive estimated breeding values derived from different families in two different environments,indicating that the different families performed differently across the different rearing sites.The families G17 and G08 performed better in factory system,while the G58 was most excellent families in pond system.(5)Study on the growth and development of Litopenaeus vannamei under different culture modesIn order to compare the growth rules of L.vannamei in different culture modes,model fitting method was used to study the growth rules of L.vannamei in the whole culture-cycle under the factory and pond culture modes,and the quantitative relationship between body length and body weight was analyzed.The results indicate that the three growth equations(Logistic、Bertalanffy and Gompertz)have high fitting accuracy(R~2>0.99),Logistic equation is the best model to describe the growth process of L.vannamei under the two modes;The relationship between body length and body weight fit power function(R~2>0.99),and the growth relationship between them is allometric growth.The growth rules of body length and body weight of L.vannamei were different between the two culture modes,the inflection points of body length and body weight in factory culture were 127.97d and 174.01d,respectively,the inflection points of body length and body weight in pond culture were 101.38d and159.62d;under pond culture mode,the time point of entering the fast growth interval was earlier than that of the factory culture mode,and the time point of body length entering the fast growth interval was earlier than that of body weight in the same culture mode.The absolute growth rate of the growth traits of L.vannamei under two modes was analyzed.The growth rate of the pond culture mode was higher than that of the factory culture mode in the middle and early stage of culture,which have a promotion potential(the mean growth limit was larger).This study can provide a reference for parent prawn rearing,healthy aquaculture and selective breeding of L.vannamei. |
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