The Breed Of Crayfish (Procambarus Clarkii) For Disease Resistance And Analysis Of Heterosis

With the rapid development of the industrial scale and production value of the crayfish,and the continuous progress of the breeding mode,the demand for high-quality breeds is increased.In order to better solve the problem of breed degeneration caused by inbreeding,a variety of breeding methods are worth developed.In this study,molecular marker-assisted breeding and cross breeding were employed to provide the strategies for producing the high-quality crayfish breeds.The main results are as follows:1.On the basis of F₃breed with fast growth and large individuals,crayfish with excellent haplotypes of immune genes Resistance（R）,Anti-lipopolysaccharride factor（ALF）and Crustin2 were selected as parents to generate the F₁population（as the breeds of selected group）.The genotypes,stress resistance and disease resistance were compared between the selected group and the unselected group（natural population）.The results showed as follows:compared with the unselected group,the proportion of excellent haplotypes in the selected group was significantly increased,and the crayfish of selected group had stronger resistance to stress and disease,and the mortality of crayfish at 8 days after transport stress was significantly reduced by 60%.After 2 days of challenge by pathogens（Aeromonas hydrophila,Vibrio parahaemolyticus,or white spot syndrome virus）,the mortality was significantly reduced by 20%.Based on the above results,the crayfish breeds of selected group,which was resistant to stress and disease,was named"Huachizhen 1".In addition,compared with the unselected crayfish population,the proportion of heterozygote genotypes of R,ALF and Crustin2 in adult crayfish population and their disease resistance were significantly increased,indicating that heterozygotes of these genes also had strong stress tolerance and disease resistance.2.By hybridizing of three different crayfish populations（Poyang Lake population,Dongting Lake population and Hong Lake population）,the progeny of different hybrid combinations（Poyang Lake（P）×Dongting Lake（D）and Poyang Lake（P）×Honghu（H））were obtained,and the hybrid F₁populations（DP,PH and HP）were obtained in 2021.In2022,the hybrid F₁populations（DP,PD,HP）were obtained.Growth phenotypic values and genetic diversity such as body weight,body length,carapace length,carapace width and abdomen length were compared between the hybrid F₁population and the inbred F₁population.The results showed that compared with the inbred F₁population,the hybrid F₁population had significant heterosis in terms of growth phenotype value.However,there was no difference in genetic diversity,The genetic basis of heterosis is needed to further study in future.In summary,we selected the anti-stress and disease resistance breed"Huachizhen 1"of crayfish,and found that there is heterosis in the hybrid F₁population between the crayfish populations from differet regions.Thses results can provide the foundation for the breeding and improvement of crayfish.