Comparative Reproductive Performance And Growth Characters Between Hybrid And Inbred Families,Portunus Trituberculatus

Based on six inbreeding generations of full-sib families Portunustrituberculatus for experimental material, using the single factor analysis of variance（One-Way ANOVA）, least significant difference （LSD）, multiple comparisonanalysis, analysis of covariance and monadic linear regression analysis, we comparedthe female parents’ reproductive performance,these filial generations’ growth,survivaland yield of six inbreeding generations and hybridization experiment groups. So as toquantify the effects of inbreeding on some economic characters such as reproductiveperformance,growth,survival and related to the survival of some economic characterssuch as yield of domesticated Portunus trituberculatusevaluate,and the influence ofdifferent hybridization experiment groups for the new variety breeding. The mainresults were as follows:This study quantifies the effects of inbreeding on reproductive performance ofdomesticated Portunus trituberculatus for inclusion in selective breeding programs ofthe future.The present study was conducted to assess the effects of inbreeding on themultiplication of full-sib families Portunus trituberculatus which were established byour laboratory have been studied,by comparing reproductive performance of sixinbreeding generations (F_1mto F₆m). Although the swimming crab Portunustrituberculatus females can spawn up to at most5times during a reproductiveseason,we only collected these data about larvae hatched from the first brood,whichare normally used for larval culture in commercial hatcheries. Taking F_1mgenerationPortunus trituberculatus as the control group, we systematically observed andrecorded the six following reproductive parameters:fecundity,eggproduction,fecundity per unit body weight,egg production per unit body weight,hatchability and survival rate at each stage from zoeaⅠ（Z1） to crab Ⅱ（C2）. Weassessed the effects of inbreeding on reproductive performance with One-WayANOVA statistical analysis.The effects of inbreeding on reproductive performance were estimated by regressing family phenotypic means on inbreeding coefficients.The experimental results show that, during reproductive season,compared with F_1mgeneration,in addition to F_2mgeneration outside, inbreeding had a high but nosignificant （P>0.05） effect on fecundity per unit body weight （-27.89%to-66.20%reduction per10%inbreeding） and egg production per unit body weight （-11.88%to-59.38%reduction per10%inbreeding）, but had no effect on hatchability;Analysis ofsurvival rate at each stage from zoeaⅠ（Z1） to crab Ⅱ（C2）showed that,as theinbreeding coefficient increase,the survival rate at each stage from zoeaⅠ（Z1） tocrabⅡ（C2） was also present a downward trend. These results suggest that inbreedingshould be avoided in crab breeding programs, although not all effects weresignificant.This study quantifies the effects of inbreeding on growth,survival and the yieldwhich related to survival, of domesticated Portunus trituberculatus for inclusion inselective breeding programs of the future.To make this assessment,this studysystematically bred six inbreeding generations with known parentage. During theproduction season, the experiment assessed growth,survival and yield,with One-WayANOVA statistical analysis. The experimental results show that,compared with theF₁inbreeding generation,by every per10%inbreeding coefficient increasing,theestimated inbreeding depression coefficient was-2.4%^-5.1%in full carapace width,-0.8%^-3.5%in body weight,-34.4%^-69.9%in overall survival and-33.02%^-56.26%in the yield which related to survival. And compared with the F₁inbreedinggeneration,the F3did not appear inbreeding depression phenomenon, no matter ingrowth, survival and the yield which related to survival, F₂, F₄, F₅and F₆all appeareddifferent degree of inbreeding depression than F₁in growth, survival and the yieldwhich related to survival, and had a high and significant （P <0.05） effect between sixinbreeding generations. At the harvest time,we analyzed uniformity and found thatthe variation coefficient of F₆inbreeding generation is the largest in six inbreedinggenerations, means the uniformity of F₆inbreeding generation is the worst in sixinbreeding generations, but the difference with other each generation is notsignificant （P>0.05）. The consistency in direction of the inbreeding depression coefficients for six generations lends to support to the hypothesis that inbreedingreduces growth,survival and the yield which related to survival, even though thecoefficients were not statistically significant due to high variability amonganimals.These results suggest that inbreeding should be avoided in crab breedingprograms.In order to breed new Portunus trituberculatus families, we have made effortson reproduction between full-sib inbreeding families and hybridization of two full-sibinbreeding, and we compared the growth and survival at the early stage betweeninbred lines and hybrid systems. In this experiment material, A pedigree （F₆）and B（F）3are two families at different genetic purification degree. There are fourexperimental groups, of which there are two inbreeding groups F₆₆（A♀x A♂） andF₃₃♀（B♀x B♂） and two hybrid groups F₆₃（A♀x B♂）, and F₃₆（B♀x A♂）. Interms of reproductive performance, inbreeding groups had higher amount at fecundity,egg production per unit body weight and fecundity per unit body weight than hybridgroups, and the difference is significant, especially for fecundity. But as for eggproduction and hatchability per unit body weight, the difference is not so significant,which means hybrid group did not show the advantage in reproductiveperformance;In terms of growth and survival at early stage, hybrid makesimprovement on both the two aspects from stage Ⅱ to stage Ⅴ, because compared toinbreeding groups of F₆₆and F₃₃,hybrid groups F₆₃and F₃₆had general heterosis of14.38%²5.05%in body weight,5.57%¹0.27%in full carapace width. The overallgrowth rate is F₆₃> F₆₆> F₃₆> F₃₃, and F₃₆relative to F₆₆group had the higher andextremely significant difference heterosis than F₆₃relative to F₆₆group; the heterosisof overall survival was22.49%³6.67%, showed as F₆₃> F₃₆> F₆₆> F₃₃, and F₆₃relative to F₆₆group had the higher and extremely significant difference heterosis thanF₃₆relative to F₆₆group. Results showed that hybrid groups did not show the heterosisin reproductive performance, but it did in growth and survival at the early growthstage, which laid a foundation for further breeding work of Portunus trituberculatus.Compared filial generations’ growth situation during the outdoor periods offour experimental groups, we found that at80days,100days,120days and150days, different characters of the same hybrid group had the different heterosis at the samegrowth stage, and the same character of the same experimental group also had thedifferent heterosis at different growth stages;In inbreeding groups,different charactershad the same performance with a result of F₃₃> F₆₆;These growth characters’ dailyincrement of hybrid groups had different levels of overall general heterosis （-3.50%to19.47%）. In terms of survival, survival rate of hybrid groups had significant heterosis,with a heterosis rate of24.81%and the overall general heterosis of15.99%on yieldassociated with survival. Hybrid of A family get better effect than B family both onthe growth characters and survival, which matches to the early growth research resultsof four experimental group sub-generation. Genetic difference between A and Bfamilies makes foundation for the improvement on heterosis and characters.