| Oncorhynchus mykiss as a global culture fish belongs to Oncorhynchus,Salmoninae and Salmonidae of family Salmoniformes. It is characterized by highquality flesh, high protein and unsaturated fat acids contents, no intermuscular bones,and easy to be processed, and particularly and it is the important object of aquaticbreeding and genetics research. But in recent years, product quality declining, geneticalcharacterization decline, frequent disease of rainbow trout became a more and moreserious problem. So, it is urgently needed to solve problems that achieve sustainabledevelopment of rainbow trout culture industry, selection of bloodstocks with the desiredtraits, such as rapid growth and disease resistance. It is generally accepted thatmolecular biological techniques could improve the efficiency of breeding, andaccelerate progress in selective breeding and optimization of gemplasm. In this study,we discuss the rainbow trout breeding work on selecting disease resistance andestimation of phenotypic and genetic correlation for body measurement traits in aselective breeding population of rainbow trout (Oncorhynchus mykiss) and usemicrosatellite markers to analyse the genetic diversity and growth traits in rainbow trout(Oncorhynchus mykiss).The generation two (G2) of a rainbow trout superior strain population were used asthe base population. This strain was being selectively bred by the Heilongjiang River Fishery Research Institute (HRFRI) of the Chinese Academy of Fishery Sciences(CAFS).60full sib families were developed in rainbow trout by random mating andavoiding inbreeding among full or half sibs. All pedigreed fry were infected by IHNVand cultured in the same condition. Gibbs sampling algorithm for a proper estimation ofgenetic variance components within an animal threshold model framework forresistance to IHN and the preliminary screening for resistance to IHN families inrainbow trout were done in this study. The results show that the heritability of resistanceto IHN was0.34.8families with a survival rate higher than50%in90days after IHNVinfection were obtained in the families screening study. Of which, one family (familynumber is K23) has a survival rate higher than90%. Our study provides insight intoresistance to IHN is moderately heritable, family selective breeding method forimproving the resistance to IHN should be feasible in rainbow trout.Furthermore, Single trait animal model were used to estimate the rainbowtrout’s(G2) heritability of8body measurement traits, including head length, body length,body height, body thickness, caudal peduncle length, caudal peduncle height, distancefrom dorsal fin to the snout and dorsal fin base length. The results showed that theheritabilities of these measurement traits ranged from0.131to0.313, mainly were atmiddle or low level, heritability of dorsal fin base length was the lowest one,0.131±0.039, and the highest one was body height, as being0.313±0.086. The geneticcorrelations between each pair of these traits were estimated by using Pearsoncorrelation method. The results showed that the genetic correlations ranged from0.065to0.866, and the correlation between body thickness and caudal peduncle length wasthe lowest, with a value of only0.016, and did not reach significant level(P>0.05),however, the genetic correlation between them was0.247, likelihood ratio test (LRT)statistical analysis showed it was significantly (P<0.05). The phenotypic correlationbetween body thickness and the dorsal fin base length was0.647, t test reached asignificant level (P<0.05), but the genetic correlation between them was only0.305, andthe LRT statistical analysis did not reach significance (P>0.05). These results suggestedthat not all of these body measurement traits were with the similar level of phenotypeand genetic correlation in this experimental population. Mistakes might be occurredwhen only the phenotypic or genetic correlation was considered in the design of a breeding program. Our results provided useful knowledge for the selective breeding ofbody measurement traits in rainbow trout.From the free EST database, we could achieve and develop the EST-SSRmolecular markers directly. EST-SSR markers could study the genetic diversity andgenetic differentiation of interspecies. A total of287565EST sequences of rainbow troutwere obtained and analysed from the NCBI database, resulting in81668non-redundantESTs with total length about55236.33kb. Totally990SSRs distributed in860ESTswere detected, accounting for1.31%of the non-redundant ESTs. We developed129EST-SSR primers based on the SSR information sites. We have examed theamplification with several rainbow trout DNA before17polymorphic EST-SSRmolecular markers were chose to analyse the genetic diversity and growth traits inrainbow trout.In this study，17polymorphic microsatellite markers were selected to analyze thegenetic diversity in cultured rainbow trout population including360individuals. Thelength of fragments ranged from90to348bp. The number of alleles per locus was from3to10, and the mean was5.8823.The effective number of alleles (Ne) ranged from1.9316to8.8220with an average of3.8223.The observed heterozygosity (Ho) and theexpected heterzygosity (He) varied from0.2083to0.7222(mean=0.4546) and from0.4830to0.8879(mean=0.6959), respectively. The value of polymorphic informationcontent (PIC) was between0.4470and0.8716with an average of0.6533, and this resultindicated that the level of genetic diversity was advanced (PIC>0.5).The probabilityvalue of chi-square test showed that13loci have significantly (P<0.01) deviated fromHardy-Weinberg equilibrium. In order to further study the relationship of microsatellitemarkers above and growth traits, the correlation was analyzed between17microsatellitemarkers and growth traits using the GLM procedure of SPSS19.0.As a result, twomarkers including HLJRTHRB846and HLJRTHRB779had a significant（P<0.01）impact on body weight, length, height, and width. Five markers includingHLJRTHRB281, HLJRTHRB373, HLJRTHRB418, HLJRTHRB260, HLJRTHRB436had a significant (P<0.01) impact on body length, height, weight. HLJRTHRB468had asignificant (P<0.01) impact on body weight and width. HLJRTHRB513had asignificant (P<0.01) impact on body height and weight. Two markers including HLJRTHRB291and HLJRTHRB809had a significant (P<0.01) impact on body height.HLJRTHRB131had a significant (P<0.01) impact on body width. HLJRTHRB241hada significant (P<0.05) impact on body length. Superior genotypes were obtained usingDuncan’s multiple comparison between genotypes and growth traits, it is useful toprovide basis for rainbow trout maker-assistant selection. |
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