Introduction
The sterlet is the only sturgeon species in the Hungarian section of the Danube and Tisza rivers, that is still present, and has a stabile population. The ex-situ sturgeon live gene bank of MATE (the Hungarian University of Agriculture and Life Sciences) and HAKI (Research Centre for Aquaculture and Fisheries) has a significant role in the preservation of this vulnerable species by its conservation management practice and conservation-based restocking programs. The individuals of the species are kept in earthen pond conditions in the gene bank of HAKI. Broodstock’s collection of sterlet in the gene bank started in the ’80-is, by capturing wild individuals primarily from Danube, Tisza, and Körös Rivers. This collection formed the basis of the recent broodstock of the sturgeon live gene bank. In the last decade, with the aim of compensate the fish stock of the locally habitat in Hungary, were no regular stocking activities. However the restoration of genetic diversity were taken into account considerably by the recent stocking programs. The goal of our research was to assesse the genetic patterns, and relationships of the recent wild population and captured stocks.
Materials and methods
For the analysis to detect, we assessed the genotype of individuals with 12 microsatellites (DNA) markers from a wild population. The examined wild fish originated from Hungary parts of river Tisza and Danube, from ex-situ gene bank and two fish farms. The fish of the gene bank was marked with individual tags, this way we could collect genetic data on the individual level. For the analysis, we took samples from the tissue on the caudal fin. DNA isolation was conducted using the E.N.Z.A. kit tissue DNA (Omega Bio-tek Inc.) method, following the instructions set by the producer. We used 100 ng DNA per sample for the PCR reaction and 12 microsatellite markers for the genetic analysis into six PCR multiplex sets. Composition of PCR reaction based on the protocol of producer (Multiplex PCR Plus Kit, Qiage). The amplified products were determined using ABI 3130 sequencing (Applied biosystems, USA). The allele number and size were identified by the Gene Mapper (Applied Biosystem) software. The standard population genetic calculations were delivered by the GenALEx 6.5 statistical software package, and the discriminant analysis by R-program.
Results and discussion
As a result of the genotyping, we detected 126 alleles on the 12 loci. The population genetic values were calculated including the number of alleles, the number of effective alleles, the observed and expected heterozygosity, the fixation index (Table 1). The average allele numbers for the group varied between 5.33 and 9.8. The average values of fixation index per population were close to zero in all populations, in the Tisza population this value was even negative. The average expected heterozygosity (He) were between 0.52 and 0.59, while the observed (Ho) values were between 0.47 and 0.60.However, the differences were small, statistically significant differences were observed in the case of the most alleles.The gene bank group reached, the highest genetic diversity, we conclude it likely represents the population of the Middle Danube and its tributary Tisza river.
The gene bank group reached, the highest genetic diversity, we conclude it likely represents the population of the Danube and its tributary Tisza river. The broodstock is a considerable gene resource and can support appropriate breading material for the restocking program. The PCA plot (Fig. 1) showed that the individuals from two fish farms were clearly separated from the wild and the gene bank groups. The wild and gene bank populations were overlapping markedly. Although the two farm stocks are separated from the wild and gene bank groups the FST values were not indicating considerable genetic differentiation between farmed and captured populations (FST values are varied between 0.016 and 0.119). In the stocked aquaculture appears the sign of bottleneck effects. The results could be used for proper broodstock management to prevent inbreeding and detect the rare alleles and to preserve maintain genetic diversity of sterlet populations.
References
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