The article describes the cytogenetic parameters of seed progeny of Pinus sylvestris plus trees growing in the Petrozavodsk seed orchard of the first order. P. sylvestris normal trees from the natural pine phytocenosis in the Pryazha region (Karelia) were taken as a control. The following indicators were considered: relative DNA content, number of chromosomes, frequency and types of mitosis pathologies at the metaphase, anaphase and telophase stages (in % of the total number of dividing cells at the same stages). It was found that the root meristem of the P. sylvestris seed progeny contains 24 chromosomes in the diploid set. Single aneuploid cells (2n = 23; 2n = 25) were found in the studied plants. The most frequent is monosomy (2n = 23). It made up 81 % of the total number of aneuploid cells. The relative DNA content in the young needles of pine seedlings of plus clones and normal trees was 42.07±0.21 and 42.95±0.04 pg, respectively, and the difference between the two was statistically significant (U-test, p ˂ 0.01). Cytogenetic analysis revealed 7 types of mitosis pathologies: chromosome fragmentation, chromosome bridges, chromosome overlap, isolation of chromosomes and groups of chromosomes, chromosome lagging, multipolar mitosis and complex abnormalities. Chromosome overlap was the most common pathology in the general mitotic disorders spectrum. Comparison of mitosis pathologies in two general samples of normal trees and plus tree clones showed that they significantly differ by the following mitosis abnormalities: overlap and isolation of chromosomes in metaphase, fragmentation, lagging, bridges and multipolar mitosis in the anaphase and telophase. The study shows that the proportion of cells with mitosis abnormalities in the seed progeny of normal trees was about 1.5 times higher than of plus tree clones, and is equal 3.44±0.32 and 2.38±0.14 % (U-test, p = 0.05), respectively. The data obtained demonstrate the cytogenetic stability of the seed progeny of P. sylvestris clones from the Petrozavodsk seed orchard of the first order, which in turn may indicate the high quality of the seed material. For citation: Ignatenko R.V., Ershova M.A., Galibina N.A., Raevsky B.V. Cytogenetic Characteristics of Seed Progeny of Scots Pine Plus Tree Clones in Karelia. Lesnoy Zhurnal [Russian Forestry Journal], 2022, no. 1, pp. 9–22. DOI: 10.37482/0536-1036-2022-1-9-22

The use of biotechnological tools, in particular somatic embryogenesis (SE) for mass propagation of conifers, is relevant since this method allows to quickly replicate plant material with desired features. However, there are still a number of difficulties in obtaining an embryogenic cell culture for Pinus sylvestris. One of the important and unsolved problems is the search for SE-competent genotypes. We cultured 674 megagametophytes from 22 donor plants (16 genotypes) in vitro during the 2021 summer period. As a result of the experiment, callus formation was not recorded for the studied genotypes; however, 9.4 ± 1.0% of the explants formed plants. In addition to the genotype effect, unsuitable nutrient medium or late developmental stages of zygotic embryos could be the reasons for the lack of callus induction. To solve these problems, a number of studies were carried out: (1) the effect of the nutrient medium composition and density (MS, MSG, ½LV, DCR) on the callus initiation from mature seeds was analyzed, (2) the effect of various growth regulators concentrations on the initiation of callus formation was studied, (3) the analysis of the reproductive competence of donor plants was performed by the method of vegetative buds cultivation. As a result, several genotypes were found to have the ability for embryogenic callus formation, and the conditions for explants cultivation were selected.

Summary: This work is part of a project investigating the heartwood formation process in Scots pine. Despite the economic and ecological importance of pine heartwood (HW), the process of its formation in many respects remains poorly understood. Scientists believe that HW formation in Scots pine begins at 9–20 years, however, systematic studies of HW initiation age in this species have not previously been conducted. Samples were collected from 105 P. sylvestris trees aged 10 to 25 years, growing in the middle and northern taiga subzones, as well as on the border of the northern taiga subzone with the tundra. Samples were taken at the trunk base according to a single technique and processed using two biochemical (peroxidase activity, pinosylvin presence) and two anatomical markers (presence of extractives on the tracheid pit membranes, nuclei disappearance) characterizing different events during HW formation. Biochemical markers showed an overestimation in the number of HW annual rings compared with HW determination based on anatomical criteria by 1–3 years, on average. Attempts to detect peroxidase activity showed a negative result in the inner sapwood annual ring, while detectable pinosylvin accumulation occurred in the transition zone (TZ). We have detected for the first time true HW (without living cells) in Scots pine samples with a cambial age (CA) of 15–17 years. The number of growth rings in TZ and HW in young trees depended on growth conditions. These results are important for understanding the mechanisms of HW formation and developing realistic models of this process, including changing climate conditions.

The use of somatic embryogenesis (SE) technology for the large-scale production of conifers demands a comprehensive understanding of its molecular basis. In this study, we identified and functionally characterized genes encoding key transcription factors (TFs) regulating SE (AILs, LAFLs, WOXs, PKL, VAL) in Picea abies (L.) H. Karst. genome. The expression profiles and patterns of the selected genes were determined by qRT-PCR in three distinct stages: (1) the formation of PEM from a zygotic embryo, (2) the initiation of ESM formation on the surface of a zygotic embryo, and (3) the proliferation of ESMs differing in morphology (white and light-yellow) and culture duration. It was determined that the prolonged subculturing of embryonal-suspensor masses (ESMs) on a medium containing plant growth regulators resulted in a decrease in the expression of identified genes. The molecular markers (among genes regulating SE) during ESM proliferation (outside the influence of the zygotic embryo) differ from those active at the embryogenic culture initiation stage. The present study proposes molecular markers of embryogenic competence of proliferating cell cultures. In silico analysis of cis-regulatory elements in promoter regions of genes revealed a total of 105 cis-elements. The most significant group, both in terms of the number of individual motifs and their occurrence, is associated with the influence of various abiotic factors. Furthermore, the investigation revealed the presence of motifs that function as binding sites for transcription factors (TFs) associated with auxin and auxin-related signaling pathways within the promoters of all the genes studied.