CYTOGENETIC MARKERS FOR SELECTION MATERNAL TREES OF SCOTS PINE AND WHITE SPRUCE PRODUCING SEED OFFSPRING WITH CERTAIN LEVEL OF GENETIC STABILITY

Currently, the depletion of the gene pool of forest woody plants is observed due to the fact that in the course of selective felling, specimens valuable for economic characteristics were destroyed and seeds from the remaining specimens were used, which did not have the best qualities. It was noted that a high level of genetic heterogeneity allows the population to adapt to changing environmental conditions, ensures the stability of the population and is a resource for breeding. The selection of valuable genotypes in the creation of forest seed plantations, which is carried out according to the phenotype, is based on the heterogeneity of populations. Meanwhile, studies show that phenotypically normal trees do not always produce good offspring. The cytogenetic method allows assessing the offspring. With its help, it is possible to distinguish among the seed offspring the mother trees of the group with different levels of stability of the genetic material. The aim of the work was to identify markers among cytogenetic parameters for the selection of trees producing seed offspring with different stability of the genetic material. The objects of the study were seedlings of seeds of phenotypically normal Scots pine trees growing in the Khopersky State Nature Reserve (51°10’56.9″N 41°44’17.2″E), and white spruce growing in the Botanical Garden. prof. B.M. Kozo-Polyansky Voronezh State University (51°42’41.57 «N 39°12’17.57″E). The trees had no visible pest damage. The method of preparation and analysis of preparations of seed sprouts is described in the work of Butorina A.K. (2000). In the course of the study, 20 cytogenetic parameters were determined: the mitotic index (counted with and without taking into account cells at the prophase of mitosis), the level of mitotic pathologies (counted with and without taking into account cells at the prophase of mitotic), the proportions of cells at the stages of prophase, metaphase, anaphase , the proportions of cells with 1–10 nucleoli in the nucleus of interphase cells, the proportion of cells with micronuclei, the proportion of cells with residual nucleoli in interphase and mitosis. Statistical processing of the study results was carried out using the STADIA 7.0 and MedCalc 17.5.3 software. The diagnostic value of the indicator is characterized by the area under the ROC-curve: 0.9–1.0 – excellent; 0.8–0.9 – very good; 0.7–0.8 – good, 0.6–0.7 – average, 0.6 and less – unsatisfactory. Among the cytogenetic indicators, there are those that are suitable for separating the mutable group from the weakly mutable and intermediate, as well as the weakly mutable from the intermediate. In pine, these include the proportion of cells at the prophase stage and the average number of nucleoli in the nucleus, in spruce – the mitotic index without taking into account cells at the prophase stage, the level of mitotic pathologies with and without taking into account cells at the prophase stage and the proportion of cells at the metaphase stage. There are indicators that make it possible to distinguish the mutable group from the weakly mutable and from the intermediate, but are not suitable for separating the weakly mutable group from the intermediate. These include the mitotic index, calculated taking into account cells at the prophase stage in pine, and the proportion of cells at the metaphase and ana-telophase stages in spruce. According to some indicators, it is possible to distinguish the intermediate group from the mutable and the weakly mutable, but it is impossible to distinguish the mutable group from the weakly mutable. In pine, such indicators are the proportion of cells in the metaphase, and in spruce, the proportion of cells with residual nucleoli in the interphase and meta-telophase. Indicators have been identified that make it possible to distinguish only mutable group from weakly mutable (in pine, the proportion of cells at the ana-telophase stage), and weakly mutable group from intermediate (in pine, the mitotic index taking into account cells at the prophase stage, the level of mitotic pathologies with and without taking into account cells at prophase stage, in spruce – mitotic index, taking into account cells at the prophase stage, the proportion of cells with micronuclei).