The dissertation is devoted to the study of the variability of the genetic structure of rainbow trout (Oncorhynchus mykiss Walbaum, 1792) (Salmoniformes, Salmonidae), cultured in local stocks of Ukraine using a complex of methods of molecular biology, population genetics and analysis of variance.
The comprehensive analysis of rainbow trout of local stocks of farms in Ukraine made it possible to reveal the features of variability at the genetic and morphological level.
The analysis of the variability of the genetic structure of rainbow trout in farms in Ukraine for the use of microsatellite loci has been carried out. It was found that the selected panel of SSR-markers had a high information content and a degree of polymorphism, which allowed determining the specificity of each local stock (average PIC value = 0.785). The specific ranges of each local stocks were shown and the allelic diversity by selected loci was characterized. A high level of genetic diversity of rainbow trout from local stocks was established (uHe = 0.825 ± 0.030; I = 1.836 ± 0.127. The AMOVA test results for microsatellite marker stated that 86% of the variability was recorded across all local stocks.
The gene pool profile of rainbow trout farmed in Ukraine was characterized using ISSR markers. It was found that 92.94% of the obtained amplicons were polymorphic, and the information content of the selected ISSR-primers was at a high level (PIC = 0.24, PPB = 92.2%; EMR = 14.8; MI = 4.1; Rp = 14.5), which makes it possible to use them to study the rainbow trout gene pool and monitor its state. For each ISSR marker, we established amplicon ranges, conservative and major bands typical of rainbow trout.
The peculiarities of genetic structure variability of rainbow trout in local stocks were studied based on protein polymorphism of transferrin (TF), posttransferin (PTF), esterase (EST) (EC 3.1.1.1.), аnd albumin (ALB) loci. Transferrin locus was represented by a triallelic system, in contrast to the other proteins studied, which were biallelic. The relative electrophoretic mobility of the studied polymorphic proteins of blood plasma were established; in the future, it can be used for interspecies comparison and species identification. The peculiarities of the distribution of alleles were shown, where, at EST and PTF locus, the slow migrating (S) was found with a higher frequency (0.617 ± 0.013 and 0.575 ± 0.076 respectively). According to albumin locus, the mean frequency of the fast-migrating (A) and slow migrating (B) alleles were 0.515 ± 0.082 and 0.485 ± 0.082. At transferrin locus, which was the most variable among proteins in fish, the three identified alleles were found in equal proportions and were: allele A — 0.318 ± 0.024; B — 0.35 ± 0.008; C — 0.331 ± 0.023. When comparing the distribution of allelic frequencies between local stocks, only the Kharkiv local stock differed in the distribution of the frequencies of allelic variants at the ALB locus. The differences between different age groups were investigated and it was found that the existing differences in the distribution of allelic variants were of local conditioning. The characteristic changes for each locus with age, which would have been observed in all the studied local stocks, were not found. The groups were assessed according to the level of heterozygosity and it was found that for all loci the values of the expected heterozygosity ranged from 0.48 to 0.49; the observed heterozygosity was 0.54 – 0.75; the fixation index ranged from 0.12 to -0.53.
The morphological variability of individuals of rainbow trout of local stocks of farms in Ukraine was also studied. Based on the analysis of the values of the coefficient of variation of the linear-weight parameters, it was in the range of 5.16 – 33.10%, it was shown that the studied local stocks had the greatest variation in weight (average Cν = 23.6%) and the average variation in the highest body depth and the largest body girth (average Cν was 8.5 and 8.6% respectively). Variability in linear growth parameters (largest body girth, highest body depth, body length without caudal fin, fork body length) and the differentiation of the studied local stocks according to the analysis of the distribution of rainbow trout individuals in the space of the first two components, reflected 96.9% of the total morphological variations according to the selected characteristics.
For the first time, data were obtained for the use of a complex of methods for analyzing the variability of rainbow trout cultivated in the conditions of trout farms in Ukraine at the genetic and morphological levels, which was a methodological basis for studying and monitoring changes in the structure of local stocks caused by factors of various nature. The methodological approach used is useful for solving the problems of ichthyological research and fish culture practice for rational resource management at trout farms in Ukraine.
