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Hybridizace jeseterů
SHIVARAMU, Sahana
The present study focused on different types of hybridization and their impacts on compare reproductive features (fertilization rate and hatching rate) and, fitness-related traits such as growth rate, cumulative survival rate, critical swimming speeds and specific growth rate in different sturgeon species, as well as level of heterozygosity among sturgeon hybrids and purebreds using set of microsatellite loci. Production of intraspecific hybrids between different populations is one of the effective strategy in aquaculture in order to obtain better offspring. Additionally, it is pivotal to monitor the genetic condition of the stocks before producing hybrids. The population genetic analysis of Danube and Volga population of sterlet showed that both the populations are genetically divergent. Additionally it revealed the gene diversity and level of heterozygosity was high in Danube population compared to Volga population. The intraspecific hybrids produced between Danube and Volga sterlet were subjected to performance tests. The significant effects of hybrid vigor were recorded in terms of average weight and cumulative survival of produced hybrids as well as reproductive features like fertilization rate and hatching rate. The results from critical swimming speed in changing temperatures assessments revealed no significant differences among the purebred and hybrid crosses which indicated no effect of intraspecific hybridization on critical swimming speed in juvenile stage. The mean number of alleles and level of heterozygosity was significantly higher in one of the reciprocal hybrid. This suggests us that it is not just production of hybrids but it is always necessary to take the position of the individual population in a hybridization matrix. Detailed investigation of fitness-related traits (growth rate and cumulative survival) in purebreds of Russian sturgeon and Siberian sturgeon and their interspecific hybrids were undertaken. Russian sturgeon and Siberian sturgeon belongs to same ploidy level (Recent tetraploids). Our results revealed both the hybrids (reciprocal) performed better than both the parent species in one of the fitness-related traits examined. One of the hybrid (Russian sturgeon × Siberian sturgeon) recorded best growth rate and its reciprocal hybrid recorded the best survival rate (Siberian sturgeon × Russian sturgeon). Although no significant difference was observed in the heterozygosity levels among the purebred and hybrid crosses, the mean number of alleles was significantly higher in Siberian sturgeon × Russian sturgeon hybrid. Experimental interbreeding of sturgeon species (sterlet and Siberian sturgeon) bearing different ploidy levels and chromosome numbers, followed by molecular investigation of obtained progeny and examination of fitness-related traits revealed one of the hybrid performed better than purebreds. Additionally the heterozygosity levels were significantly high in one of the hybrid. The general rule of the negative interaction which could occur between the parental genes with different ploidy and its apparent impact on the intergeneric hybrid genome was not supported in our study. Therefore, given the evidences and observations provided by this study in controlled conditions, the above mentioned intraspecific and interspecific hybrids could be suggested for intensive aquaculture and might be also suitable for polyculture stocks. With respect to the growth properties of the monitored hybrids, these hybrids may present a significant competitive risk for wild populations of pure sturgeon species, in the event of their release into wild. Added to that, due to the easy hybridization of sturgeons in aquaculture conditions, as well as in natural waters, presents a considerable potential for this issue for further scientific research aimed at using different types of hybrids in aquaculture, as well as their impact on pure species in natural waters.
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Odhad genetické variance užitkových vlastností kapra obecného s cílem předpovědět potenciál selekčního šlechtění v rybničních podmínkách chovu
PRCHAL, Martin
The main aim of this thesis was to study the genetic variation of several performance traits under pond management conditions and to estimate future perspective of sustainable selective breeding program in common carp. In the present study, Amur mirror carp (AM) and Hungarian synthetic mirror carp (HSM) were used. Most of the studied performance traits showed sufficient genetic variation (h2 = 0.12 1.0), suggesting a good potential for genetic improvement of the traits through selective breeding. It was shown that selection of common carp under pond management conditions should be optimally applied after the second overwintering. Winter survival is often a bottleneck for common carp production. As a result, the genetic background of winter survival and traits that might be correlated to the survival was studied. Main focus was given to the muscle fat and body weight and their dynamics through winter period and successive third growing period. It was found that selection for i) lower fat content before and after winter, ii) lower decrease in muscle fat content and/or body weight during winter, iii) higher condition factor may lead to better survival during both winter and third growing period and growth of fish during the third growing season. Unfortunately, direct selection for slaughter yields is impossible on live breeding candidates. Therefore, morphological predictors that can be measured in vivo are considered as an interesting alternative. As a result, external and internal measures were combined on 1553 fish by linear regression to predict log-log residuals (Logr) of slaughter yields. It was found that the accuracy of the prediction of slaughter yields may be solid. From the genetic point of view, model-predicted (h2 = 0.48 0.63) and even individual predictors (h2 = 0.34 0.72) of slaughter yields were highly heritable and favourably genetically correlated to the Logr yields. Hence, selection on trait predictors has an interesting perspective for genetic improvement of slaughter yields in common carp. Furthermore, genetic parameters of fillet fatty acid content and performance traits in market size common carp cultured under semi-intensive pond conditions were estimated. For flesh FA composition analysis 158 individuals were processed. Heritability estimates of total muscle fat, some FA groups and most performance traits were moderate to high (0.23 0.62). Interestingly, genetic correlations showed that genetic improvement of growth via selective breeding under Central European pond conditions without changing the production technology would very likely negatively affect carp flesh quality with respect to FA composition. Finally, restriction-site-associated DNA sequencing (Rad-seq) was used to identify and genotype single nucleotide polymorphism (SNP) markers for subsequent parentage assignment, construction of a medium density genetic map (12,311 SNPs), and testing of efficiency of marker-assisted (MAS) and genomic selection (GS) for growth and Koi herpes virus (KHV) resistance. No genome-wide significant QTL was identified for growth. However, genomic prediction of its breeding value may outperform the traditional pedigree-based prediction, resulting in an 18% improvement in prediction accuracy. On the other hand, genome-wide significant QTL affecting resistance to KHV was identified on linkage group (LG) 44 explaining approximately 7% of the additive genetic variation. The presented results add further evidence supporting the application of selective breeding in common carp cultured even under traditional pond management conditions. However, it is evident that the rearing technology will need suitable modifications. In addition, real economic impact of selective breeding on carp culture should be verified by calculation of realized heritabilities, real genetic gains and the total fish biomass yield of genetically improved stocks from a pond area unit.
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