DNA polymorphism and genetic diversity of the oak lace bug (Corythucha arcuata Say) population in Krasnodar Krai

One of the directions of insect population genetics is the study of the variability of the genetic structure of populations, which includes the assessment of genetic diversity, DNA polymorphism and genetic similarity of the studied objects. This makes it possible to judge the flow of genes, i.e. exchange of genetic material within a population or between populations, and determine the degree of their genetic differentiation, i.e. they represent different populations or one population, and in this case, they are intrapopulation groupings. The aim of this work was to study the molecular genetic structure of local populations of the oak lace bug C. arcuata in Krasnodar Krai using RAPD markers to assess their genetic similarity. We carried out the studies in the territories of the invasive distribution of the oak lace bug in Krasnodar Krai in 2020. The object of the research was a sample of insects (n = 20) from the areas of oak lace bug in the forest park zones of Krasnodar, Tikhoretsk, Krymsk and Sochi. The total number of samples examined was 240. We collected C. arcuata bugs on model trees of English oak (Quercus robur L.). The selection of trees was 10 oak trees from each locality. Isolation of DNA from whole insects (adults), amplification RAPD-PCR (random amplified polymorphic DNA) and electrophoresis were carried out according to the method we had developed earlier (Kil, 2009). Amplification was performed in 25 mcl reaction mix containing 10 mM Tris-HCl, pH 9.0; 50 mM KCl; 3.0 mM MgCl₂; 50 pM of each dNTP; 0.8pM primer; 0.5 U Taq polymerase and 20 ng DNA. We evaluated DNA polymorphism of the studied samples from the population of bugs using three primers highly specific for the DNA of the oak lace bug: OPA07, OPA09, OPA18 (See Fig. 1 and Table 1). We assessed genetic diversity and genetic similarity using the Nei and Shannon information indices with the help of POPGENE computer program (version 1.31) (Yeh et al., 1999). The statistical significance of the differences between the mean values for the sample was determined by the Student’s t-test (p < 0.05). Molecular genetic analysis of C. arcuata revealed high levels of DNA polymorphism and genetic diversity in the oak lace bug population and the absence of significant differences between the samples for these parameters (See Table 2). The studies have shown that the closest in genetic terms are the samples from Tikhoretsk and Krymsk (genetic identity (GI) = 0.998; genetic distance (GD) = 0.003), and the most genetically distant from others are the Krasnodar and Sochi intra-population groupings (GI = 0.942; GD = 0.06) (See Table 4). This was also demonstrated by the cluster analysis of data (See Fig. 2). Genetic diversity, estimated by Nei index, within four geographic samples (Hs = 0.275) was 93.2% of the total genetic diversity in the lace bug population (Ht = 0.295) (See Table 3). This indicates a significant level of gene flow between intra-population groupings (Nm = 6.98), which prevents their differentiation. The low value of the coefficient of genetic differentiation (Gst = 0.07) indicates that only 6.8% of the total genetic variability of the population is accounted for by the variability between intra-population groupings. Based on this, we can conclude that the analyzed insect samples represent intra-population groupings from one population of oak lace bugs, C. arcuata. The paper contains 2 Figures, 4 Tables and 39 References. Abbreviations: GI - Genetic Identity; GD - Genetic Distances. The Authors declare no conflict of interest.

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