Evaluation On Selection Effect Of The Seventh Generations Of Strain Selection In Macrobrachium Rosenbergii And The Analysis Of Genetic Diversity In Different Generations

M.rosenbergii was known as Malaysian prawns and fresh water long-brachium prawns,it belongs to the Phylum arthropoda,Crustacea,Decapoda,Macrobrachidae,and Biogas genus.It was from south of Asia,northe of Pacific and other regions.It was introductioned to China from Japan in 1976.M.rosenbergii has become an important freshwater prawns species in China.Thanks to its advantages such as delicious meat,fast growth,strong disease resistance and easy cultivation,as well as the breakthrough in artificial seedling cultivation technology,the promotion and breeding of M.rosenbergii.But,after many years of artificial breeding and cultivation,it increased the disease,individual miniaturization,slow growth speed,sexual maturation time in advance,resistance to abate marks the germplasm degradation phenomenon is increasingly prominent.Especially in recent years,pool have roche spermatogenesis phenomenon of large area happened for successive years,the slow growth seriously affect the spermatogenesis of aquaculture production and economic benefits.There have been many reports on the germplasm resources of M.rosenbergii in recent ten years.At present,the germplasm resources as well as the breeding of superior species of M.rosenbergii have been carried out,such as the breeding of South Taihu Lake No.1 and No.2.In order to further promote the production of M.rosenbergii seedlings.This paper studied their factors such as the shrimp phenotypic,genetic,specialized for the growth of roche expounds five strains are seven generations and Shanghai local breeding population growth comparison,and then using microsatellite marker technique to the roche expounds five growth specialized strains,genetic diversity analysis and using the diallel cross design to roche expounds five growth specialized lines form a combination of form a complete set of 25,using additive-dominant genetic model of the hybrid combinations offspring five growth shape analysis of combining ability,analyze their combining ability,heterosis and genetic force,etc.,form a complete set of effective combination.Then,the genetic diversity of three generations,growth specialized-lines and disease-resistant specialized-lines bred in our laboratory were analyzed by microsatellite,and the breeding status and genetic potential of M.rosenbergii were evaluated in each specialized-line population and each generation during the breeding process.It provides a theoretical basis for molecular assisted breeding in macrobrachium rosenbergii.The specific research content is as follows:1 Growth comparison and genetic diversity analysis of seven generations of five fast growing specializedstrains of M.rosenbergiiThis experiment studied the growth performance and compare between 5 fast growing specialized-breeding lines（A2,A3,B3,C2,C3）and the no-breeding group（Shanghai）.The final weight of A2,A3,B3,C2 and C3 was higher than that of the no-breeding group（Shanghai）..The relative weight gain rates were 33.33%,110.73%,53.67%,85.28%and 47.17%,respectively.The absolute weight gain rate of the five breeding lines was significantly higher than that of the non-breeding group F,and the size order was A3>C2>B3 C3>A2>F.The proportion of A2,B3 and C3 in line with the body shape was increased.The proportion of A2 and C2 lines was slightly decreased.The genetic diversity of 5 selected lines of M.rosenbergii and non-breeding populations in Shanghai was analyzed by using 25 pairs of Microsatellite molecular marker primers.The results showed that the genetic diversity index of A3 was low,the observed allele number（Na）was 1.92,the average effective allele number（Ne）was 1.585,the observed heterozygosity Ho was 0.348,the expected heterozygosity He was 0.308,and the PIC content of polymorphism information was 0.247,belonging to low-degree polymorphism.The genetic diversity of A2 and F populations was higher than that of other populations,belonging to moderate polymorphism.By comparing the genetic diversity of different populations,it can be seen that the breeding effect of breeding population is obvious.2 Analysis of the Combining Ability,Heritability and Heterosis of Crossing Effect of Five Matching Breeding Lines in Seven GenerationsIn this experiment,General combining ability was not detected in 5 growth traits,indicating that these 5 traits were mainly controlled by non-additive effects of genes.The special combining ability of A3×C2 combination and the predicted value of the special combining ability were both better,which showed a good positive hybridization effect.The body length and body weight of self-cross combination and B3×C3 combination showed negative effects.All of the 5 selected lines showed good heterosis through diallel hybridization.The predicted values of H_M and H_B were also consistent with the positive effects of most of the hybrid combinations on average heterosis（H_M）and superheterosis（H_B）.The combination of A3×C2,B3×C2,and A3×B3 showed heterosis,which was consistent with the results of large genetic distance between A3 selective lines and other selective lines in chapter 1.This experimental study showed that A3×C2,B3×C2,and A3×B3 showed greater heterosis,which could help us better improve and improve the next step of breeding.3 Analysis of genetic diversity in different breeding populations of M.rosenbergiiThis research explored the genetic diversity of different generations of M rosenbergii in terms of population and generation,providing a theoretical basis of the breeding and genetic improvement for Specialized Breeding Lines.The research used25 pairs of microsatellite markers with good polymorphism to analyze the genetic diversity of different generations of M.rosenbergii of Thai population,fast-growing population and disease-resistant Specialized Breeding Line Population.The results of the Thai population showed a down trend in the extent of genetic diversity of the three generations from generation to generation.Including,the number of effective alleles decreased from 2.5937 to 1.8565;the expected heterozygosity decreased from 0.5641to 0.4280;the polymorphism information content decreased from 0.5008 to 0.3630.The results of fast-growing specialized breeding lines population demonstrated downtrend extent of genetic diversity,including the polymorphism information content of breeding line SA3 decreased from 0.3827 to 0.2560;SC2 decreased from0.3877 to 0.2557;KB3 decreased from 0.2952 to 0.2845,KA2 decreased from 0.3721to 0.2974.Although there was weak connection difference between generations（P<0.05）;The expected heterozygosity（KB3:He=0.3580,KA2 He=0.3602）of the breeding lines with specialized disease resistance F₂ was greater than that of the breeding lines with specialized growth F₃（SA3 He=0.3188,SC2 He=0.3131）.The results emerged that breeding of matching lines could reduce the genetic diversity index of each generation.It could be regarded as a criterion for evaluating the breeding effect of fast-growing specialized lines.However,the selection criteria of specialized disease resistance breeding lines is required to combine with other criteria such as heterozygosity change,infection survival rate and breeding survival rate.