Study On The Combining Effects Of Complete Set Line Breeding In Common Carp And Tilapias

In China,high generation breeding populations of aquatic organisms have been accumulatively increased accompanied with the development of aquaculture breeding progress,however,the inbreeding depression have been occurred in practices. There is an important issues to how to take advantage of their excellent germplasm of high generation breeding populations,such as high genetic homogeneity and stable targeted breeding traits. In this paper,the three high generation breeding varieties of common carp, Xingguo red common carp(Cyprinus carpio var. singuonensis), Purse red common carp(Cyprinus carpio var. wuyuanensis),Glass red common carp(Cyprinus carpio var. wananensis) and three strains of Nile tilapia(“New GIFT”, “GIFT”, “Genomar”)were used as the model materials,the phenotypic and genetic variation of complete set lines and the combining effects of combinations in common carp and tilapia were studied using the methods of molecular genetics and quantitative genetics. The aims of these studies is to enrich and develope the theory of complete set line breeding in fish and the method in analyzing the morphological data of fish,meanwhile,to establish the theoretical basis in selecting the best combinations and new varieties of tilapia. The details of these studies are presented as follows: 1. Studies on the genetic background of the complete set lines in high generation breeding varieties of common carp, Cyprinus carpio L.In this section, three high generation breeding varieties of common carp(Xingguo red common carp,Purse red common carp,Glass red common carp) were used as the topic group,and colored carp(Oujiang color carp,Koi carp,Long-fin carp) and wild common carp(Yangtze River wild common carp,Oujiang wild common carp,Zhujiang wild common carp,Amur River wild common carp and European wild common carp) and domesticated carp(German scattered scale mirror carp) were regarded as the reference groups,the genetic background and variation of these common carps was analyzed by the complete mitochondrial sequences and microsatellite molecular marker technology. The complete mitochondrial sequences of nine common carp were determined,including Glass red common carp,Long-fin carp,Koi carp,Yangtze River wild common carp,Zhujiang wild common carp,Oujiang wild common carp,Amur River wild common carp,Hungary wild common carp and German scattered scale mirror carp. The results of clustering analysis based on the three methods of Mr Bayes,MP,ML in complete mitochondrial DNA,protein coding sequences,D-loop region showed that the largest relationship existed between Purse red common carp and wild common carp and the closest existed between Xingguo red common carp and wild common carp,suggesting that the red common carp in China would had originated from the colored carp. Furthermore,the genetic variation,cluster analysis,principal component analysis,STRUCTURE genetic clustering analysis were also carried out based on the eight microsatellite molecular markers,the results illustrated that the genetic diversity of complete set lines were lower than that of the colored carp and wild carp populations. The two common carps from European(Hungary wild common carp and German scattered scale mirror carp) were clustered together,the four strains of wild common carp(Amur River wild common carp, Zhujiang wild common carp,Yangtze River wild common carp,Oujiang wild common carp) were clustered together with Glass red common carp and Xingguo red common carp,the two colored carp(Oujiang color carp,Koi carp) were clustered together with Long-fin carp and Purse red common carp. The populations of complete set line were clustered into two categories with obvious genetic variation among them,indicating they would be good candidate to carry out the complete set line breeding. 2. Studies on combination effect in high generation breeding varieties of common carp, Cyprinus carpio L.There is an important problem that how to persistently utilize their germplasm resources of high generation breeding varieties of aquatic organisms. In this section,Xingguo red common carp,Purse red common carp and Glass red common carp were used in analyzing the combining ability and heterosis of five growth traits(body weight,total length,standard length,pre-dorsal height and pre-dorsal width) in F1 hybrids through 3 × 3 complete diallel cross. The results showed that the general combining ability of the five growth traits were low,but the specific combining ability were high and significant,suggesting it would be very difficult for further direct breeding in high generations selection varieties. Further analysis through heterosis illustrated that the positively average heterosis were observed within the six crosses with the average heterosis of 23.33% in body weight. The results illustrated that the high generation breeding varieties with high degree of inbreeding can be continually used to develop its excellent germplasm through complete set utilization. 3. Morphological difference of complete set line breeding populations of common carp using two data processing methodsIn this section,the complete set line breeding of three high generation breeding varieties : Xingguo red common carp,Glass red common carp and Purse red common carp,were used to conduct comparative analysis of traditional morphological methods and molecular population genetics methods in dealing with the morphological data. The results showed that the same profiles of clustering analysis were found from the two kinds of methods. The principle component analysis indicated that the traditional morphological methods can better reflect the morphological variations among individuals, while the molecular population genetics methods can better reflect the morphological differences among populations. The discriminant analysis showed the samilar discriminant accuracy of the two kinds of methods. Furthermore,the genetic clustering analysis results using software STRUCTURE illustrated the consistency of the two kinds of methods. Consequently,The results indicated that the same results from the traditional morphological methods and molecular population genetics methods in dealing with morphological data of complete set utilization in high generation breeding varieties, further illustrated that it is feasible that molecular population genetics methods conduct analyzing morphological data of common carp. 4. Studies on the combining effects of complete set line breeding of Nile tilapiaIn order to select the best combinations of Nile tilapia aquaculture,three strains of Nile tilapia(“New GIFT”、“GIFT”、“Genomar”) were used in establishing different combinations through 3 × 3 complete diallel cross,and the combining ability and heterosis of five growth traits(body weight,total length,standard length,pre-dorsal height and pre-dorsal width) in F1 combinations were analyzed. The results showed that the general combining ability were not detected in the five growth traits,but mainly affected by the special combining ability which accounted for over 62%,illustrating the heterosis would be easily obtained by complete set utilization among three strains of Nile tilapia. The results of heterosis indicated that the significant heterosis were existed in three combinations of Genomar♀×New GIFT♂, New GIFT♀×Genomar♂,GIFT♀×New GIFT♂,in which, the combination of Genomar♀×New GIFT♂was the best complete set combination. These results not only provided the foundation theory of complete set line breeding in fish, but also gave insight into new varieties development in tilapia.