Secondary metabolites of aromatic plants are used in many health applications as drugs, pheromones, insecticides, fragrances, and antioxidants. Due to the huge commercial demand for these secondary metabolites, the need to overcome the insufficient productivity of aromatic plants has become a significant challenge. Plant breeding is a traditional, labor-intensive, and limited method to improve the ability of aromatic plants to produce secondary metabolites. Modern methods of biotechnology, including genetic engineering and genome editing, can be useful and cost-effective in improving aromatic plants, as they can increase the efficiency of obtaining plants with high productivity and the creation of resistant forms and breeding lines. This review illustrates the importance of developing methods for the modification of aromatic plants belonging to different families, with a predictable quality, resistance to adverse factors and pests, and intensive growth and high yields and productivity of valuable essential oils. Particular attention is paid to successful examples of the modification of aromatic plants, applied methods, and principal approaches

In this work, we studied in vitro propagation of three cultivars of Mentha × piperita L. Murashige and Skoog medium (MS) supplemented with 0.5 mg·L⁻¹ BAP was the most optimal medium for micropropagation of the cultivars studied. The ability of peppermint plants field-acclimated after in vitro micropropagation to produce essential oils (EOs) was investigated. EO was obtained by hydrodistillation from dried leaves and flowering shoots from control (field grown) plants and plants acclimated in field conditions after in vitro propagation. The samples were collected at the first and second year of vegetation, and their chemical composition was investigated using gas chromatography-mass spectrometry (GC-MS). Differences were observed in the yield, as well as in the quantitative and qualitative composition of the EOs extracted from the control plants and field-acclimated plants after in vitro propagation. Menthol was the main component of the EO in control plants, while pulegone and menthone were dominant in the EO pattern in field-acclimated in vitro regenerants in the first year of the growing season. However, in the second year of vegetation, the content of the main EO components in field-acclimated peppermint plants was approximately the same as in control plants. The antioxidant activity of EOs extracted from field-acclimated after in vitro micropropagation plants was found to be the same as in control field-grown M. × piperita plants.

Understanding the mechanisms of plant salt tolerance as a complex trait is an integral part of many studies, the results of which have been used in the breeding process. The aim of this study was to compare the root response of two tomato (Solanum lycopersicum L.) genotypes (breeding line YaLF and cultivar Recordsmen) differing in salt tolerance. Rhizogenesis was induced in tomato shoots in vitro with different concentrations of NaCl in the culture medium. A number of morphobiological and cytological parameters were evaluated at the organ, tissue, and cellular levels for possible use in a comprehensive assessment of genotypes for salt tolerance. The influence of NaCl caused disruption of the cell cycle and redistribution of cells in the phases of the cell cycle. An increase in the degree of vacuolization was shown in cv Recordsmen at 75 and 150 mM NaCl and in the YaLF line at 150 mM NaCl. Under salt action, an increase/decrease in the length of cells such as columella cells (both genotypes) and epidermal cells (in cv Recordsmen at 75 and 150 mM NaCl) was shown. Differences between genotypes were demonstrated by changes in the area of the central cylinder and primary root cortex cells, as well as by changes of the S_nucleolus/S_nucleus ratio in these cells. Transmission electron microscopy (TEM) showed the modification of the chromatin structure in the root cells of these genotypes. Various cytoskeletal disorders were revealed in interphase cells of the tomato root of cv Recordsmen and the YaLF line by immunofluorescent staining under saline conditions. These morphometric and cytological parameters can be used for a comparative evaluation of genotypes differing in salt tolerance in a comprehensive assessment of varieties.

The study of the leafmining moth of the chestnut miner (Cameraria ohridella Deschka & Dymić, 1986) was carried out through the planting of the common horse chestnut (Aesculus hippocastanum L.) in the Main Botanical Garden of the Russian Academy of Sciences. The effect of various degrees of insolation of horse chestnut plants on leaf morphology and the composition of secondary metabolites, as well as the relationship of these parameters with the number and density of C. ohridella populations during the growing season, was studied. The solar influence, it was noted, had a significant impact. Thus, the largest number of the pests was recorded on the leaves of the sunlit side of the tree crown, and the smallest on the leaves of the shady part of the crown. The low content of polyphenols in the pool of secondary metabolites in the tissues of the A. hippocastanum leaves did not deter C. ohridella and poorly protected the plants from this miner, while the significant content of carbohydrates in the leaves reduced the resistance of chestnut plants to damage by the Ohrid leaf miner.

Crystal-bearing cells or idioblasts, which deposit calcium oxalate, are located in various tissues and organs of many plant species. The functional significance of their formation is currently unclear. Idioblasts in the leaf parenchyma and the development of crystal-bearing cells in the anther tissues of transgenic tomato plants (Solanum lycopersicon L.), expressing the heterologous FeSOD gene and which showed a decrease in fertility, were studied by transmission and scanning electron microscopy. The amount of calcium oxalate crystals was found to increase significantly in the transgenic plants compared to the wild type (WT) ones in idioblasts and crystal-bearing cells of the upper part of the anther. At the same time, changes in the size and shape of the crystals and their location in anther organs were noted. It seems that the interruption in the break of the anther stomium in transgenic plants was associated with the formation and cell death regulation of a specialized group of crystal-bearing cells. This disturbance caused an increase in the pool of these cells and their localization in the upper part of the anther, where rupture is initiated. Perturbations were also noted in the lower part of the anther in transgenic plants, where the amount of calcium oxalate crystals in crystal-bearing cells was reduced that was accompanied by disturbances in the morphology of pollen grains. Thus, the induction of the formation of crystal-bearing cells and calcium oxalate crystals can have multidirectional effects, contributing to the regulation of oxalate metabolism in the generative and vegetative organs and preventing fertility when the ROS balance changes, in particular, during oxidative stresses accompanying most abiotic and biotic environmental factors.

The susceptibility of seven species of chestnuts to the horse chestnut leaf miner was studied in the arboretum of the Main Botanical Garden of the Russian Academy of Sciences (MBG RAS), taking into account their interspecific characteristics. Using pheromone delta traps, the highest number of Cameraria ohridella moths was shown for Aesculus hippocastanum and the lowest for Aesculus chinensis. A number of anatomical parameters of leaves were investigated, such as the thickness of the epidermal cell wall and the thickness of the palisade and spongy parenchyma layers. As a result, it was shown that the most infected chestnut species had a greater thickness of the nutritious parenchyma tissue. No dependence was found between the degree of susceptibility to the horse chestnut leaf miner and such indicators as the content of chlorophyll a + b and carotenoids in the leaves of seven species of chestnuts. Nevertheless, resistance of different species of the genus Aesculus to Cameraria ohridella under increased tannin content in leaves has been shown. Evaluation of phenolic compounds and flavonoids has not established their reliable role as repellents. The high levels of carbohydrates found during the study contributed to increased susceptibility to the horse chestnut leaf miner.