ASSESSMENT OF THE GENETIC VARIABILITY OF DIFFERENT AGE GROUPS OF SILVER AND BIGHEAD CARPS BY BIOCHEMICAL POLYMORPHISM
Authors: Stetsiuk I. , Borysenko N. , Nahorniuk T. , Mariutsa A. 
Published: July 2021

Goal. The study aimed to analyze and assess the genetic variability of different age groups of silver and bighead carps by the polymorphism of protein and enzyme systems. Methods. Blood samples were taken from silver (Hypophthalmichthys molitrix) and bighead (Aristichthys nobilis) carps of "Sunpoint Ukraine" LLC, Slobozhanske, Zmiiv district, Kharkiv region. Blood from the tail vein was collected from age-2 and age-3 fish in vivo and placed into tubes with an anticoagulant. Whole blood samples were separated into fractions by centrifugation and as a result plasma and erythrocytes were packed into separate tubes. The methods of vertical polyacrylamide and horizontal starch electrophoresis were used for the electrophoretic separation of proteins and enzymes of silver and bighead carps blood. Histochemical staining of the gel plates was carried out with t) and bighead he following genotyping of allelic variants of protein and enzyme systems. Biochemical systems such as loci of prealbumin (Pralb), esterase (EST, K.F. 3.1.1.1), malate dehydrogenase (MDH, K.F. 1.1.1.37), enzyme malic (ME, K.F. 1.1.1.40) and carbonic anhydrase (CA, K.F. 4.2.1.1) were investigated. Statistical processing of experimental data was performed using Biosys-1. Cluster analysis was carried out using MEGA-X. Results. Analysis of the peculiarities of the distribution of allele frequencies and the genotypic composition of Pralb, EST, MDH, ME, and CA loci was carried out in the age-2 and age-3 groups of silver and bighead carps. The prevalence of the frequency of the fast migrating allelic variant F was revealed in comparison with the slow migrating gene at EST locus in the age-3 group of silver carp (Est F = 0.620). The prevalence of the frequency of the fast allelic variant Pralb A in comparison with the slow Pralb B was observed in the silver carp groups (Pralb A = 0.812 in the age-2 and Pralb A = 0.726 in the age-3 groups. According to the genotypic composition of the studied loci, there was an excess of heterozygous individuals in the age-2 group of silver carp, which indicates their genetic imbalance. The formation of breeding stocks of silver and bighead carps requires control of the level of genetic variability of different age groups to monitor changes in the genetic structure and maintain the optimal level of heterozygosity in stocks. The highest level of average heterozygosity (79.4%) was found in the age-2 group of silver carp, which prevailed over the expected average heterozygosity with a value of 49.4%. In comparison with other studied groups, the age-2 group of bighead carp had the lowest level of average heterozygosity of 59.1% versus the theoretically calculated level of 45.5%. The age-2 and age-3 groups of bighead carp had the highest level of heterozygosity at Ca locus at the level of 82.8 and 78.6% respectively, in contrast to the expected heterozygosity at this locus at the level of 49.9 and 49.7%. A dendrogram of the genetic relationships of different age groups of silver carp was constructed based on the values of genetic distances. The formed clusters indicated the formation of the genetic structure of the silver and bighead carps by species affiliation. Conclusions. The analysis of the genetic structure of different age groups of the silver and bighead carps was performed by the polymorphism of protein and enzyme systems such as Pralb, EST, MDH, ME, CA loci. The study describes the features of the distribution of allelic frequencies and genotypic variants of the aforementioned loci. The level of average heterozygosity, observed and expected heterozygosity at loci in age-2 and age-3 groups of silver and bighead carps were determined. The high genetic variability of an age-2 group of silver carp at the level of 79.4% indicates the need to stabilize their genetic structure. As a result of the cluster analysis, it was determined that the formation of the genetic structure of the silver carp groups of the "Sunpoint Ukraine" farm in the Kharkiv region occurs by species affiliation. The study and use of biochemical markers will allow differentiating stocks of silver and bighead carps. As well as in complex analysis with other molecular genetic markers will allow them to develop a genetic passport.