Analysis Of Resistance To Generations And Establishment Of F4 Generation Family Of Disease Resistance For Edwardsiella Tarda In Japanese Flounder(Paralichthys Olivaceus)

Paralichthys olivaceus is one of the important maricultural fish in northern China.In recent years,the large-scale industrialized breeding of Paralichthys olivaceus has developed rapidly,which has led to the economic development in many regions.The high density of factory farming and inbreeding leads to flounder germplasm degradation,frequent occurrence of diseases,the decline in output,seriously hamper the long-term sustainable development of the industry of flounder.Flounder disease are usually treated with antibiotics,but the extensive use of antibiotics can lead to drug residues in fish,lead to bacterial resistance increased,water pollution and other issues,and potential safety hazards to the health of consumers.Therefore,the use of advanced biotechnology means,a variety of advanced breeding techniques and traditional breeding methods combined to develop their own strong resistance to disease flounder varieties,help to reduce pollution,improve the survival rate of Japanese flounder culture,Increase economic efficiency.In this study,we used the methods of family selection and nuclear development,used Japanese flounder group,Korean flounder group,2009,2010,2012,2013,2014 flounder family as parent.In 2016,28 families of F4 generation of Paralichthys olivaceus were bred,including F3 generation 4 families,F4 generation 23 families and 1 contrast family.After 60 days of growth traits,the daily body length growth rate of the first 20% families in the F4 generation was defined as a rapid growing family with a total of 6,include F1639,F1621,F1661,F1606,F1648,F1647,the average daily body length growth rate is 0.166 cm/d.The daily body length growth rate of the last 30% families in the F4 generation was defined as a slow growing family with a total of 9,the average daily body length growth rate is 0.142 cm/d.The rest of the family defined as the general growing family with a total of 13,the average daily body length growth rate is 0.151cm/d.After artificial infection experiment,the survival rate of F4 generation of all families was 15.24%-77.23%,and the average survival rate was 44.48%.The survival rate of the first 20% families in the F4 generation was defined as disease resistance high family with a total of 6,include F1639,F1601,F1633,F1635,F1657,F1606,the average survival rate is 72.14%.The survival rate of the last 30% families in the F4 generation was defined as disease resistance low family with a total of 9,the average survival rate is 22.38%.The rest of the family defined as disease resistance general family with a total of 13,the average daily body length growth rate is 47.01%.Pearson correlation analysis of growth traits and disease resistance traits in F4 generation flounder family.Survival rate was positively correlated with body length,body weight and body length,correlation coefficient are length 0.496,daily body length growth rate 0.301,reweight 0.432.The results showed that there was a moderate correlation between survival rate and body length,body length and body weight.After 60 days of growth trait assay and artificial bacterial infection,F1639 was screened for F4 resistance and fast-growing families.According to the family pedigree of the generation can be seen,F1639 family of parents for the F1421,F0927,F0750,are resistant to strong families.F1639,F1421 for the resistance to Edwardsiella family,the survival rate of Edwardsiella infection in F1639 family was 77.23%,which was 32.75% higher than that of F4 on average survival rate of 44.48%.The F1421 family was selected for the generation of F3 resistant strains of high,the survival rate was 47.06%,which was 26.77% higher than the average survival rate of F3 of 20.29%.F0927,F0750 for the resistance to Vibrio family,the survival rate of Vibrio infection in F0927 family was 64.97%,which was 36.73% higher than that of F2 on average survival rate of 28.24%.The F0750 family was selected for the generation of F1 resistant strains of high,the survival rate was 64.05%,which was 31.45% higher than the average survival rate of F3 of 32.60%.After F1 to F4 generation of breeding families,the disease resistance of high family resistance to disease generation by generation,by the F1 generation of 51.86% survival rate increased to F4 generation of 72.14%.In this study,the F4 family of the flounder was resistant to Edwardsiosis,and the F1639 family with high disease resistance and rapid growth could be screened for further family screening.After several generations of breeding and artificial infection,the disease resistance of Paralichthys olivaceus was gradually improved,and the genetic basis of the low fertility resistance was homozygous to cultivate new varieties of fine flounder.The promotion of value and broad prospects for the promotion.