Vol 70, No 5 (2023)

Sunflower broomrape (Orobanche cumana Wallr.) is an obligate parasitic plant that specifically infects sunflower and can cause significant yield losses. In this regard, obtaining sunflower varieties resistant to broomrape is an important task for agriculture. Sunflower breeding for resistance to broomrape was initiated in the beginning of the 20th century in USSR. However, the production of new resistant sunflower varieties was accompanied by the emergence of new virulent broomrape races that overcame the effect of resistance genes. For a number of sunflower genetic loci that determine resistance to broomrape, the location on the genetic map was determined, but only for some of them probable candidate genes were identified and the possible molecular mechanism of their action was described. In addition, transcriptomic data have recently been obtained for broomrape-resistant and susceptible sunflower varieties, which also makes it possible to get closer to understanding the molecular basis of resistance formation. This review focuses on molecular genetic mechanisms of sunflower resistance to broomrape, identified on the basis of genetic mapping of resistance loci, determination of probable candidate genes, as well as available transcriptomic data.

Novel lines of tobacco (Nicotiana tabacum L.), highly expressing the AtNDB2 gene (NDB2 from Arabidopsis thaliana (L.) Heynh.), were produced with the help of agrobacterial transformation followed by a selection. The transgenic 13s line, possessing typical exterior and the AtNDB2 expression level, was compared with the initial wild type of N. tabacum regarding the parameters of growth and respiratory activity under optimal and suboptimal temperatures. It was found that the total and alternative respiration increased and the superoxide anion generation decreased in the 13s plants under the suboptimal temperature. The growth rate was decreased in the plants highly expressing the AtNDB2 gene in comparison with the control wild type plants, especially at the temperature below the optimum. Possible causes of the found changes are discussed.

The effect of short-term and long-term root treatment with melatonin on growth parameters, photochemical activity of PSII, content of basic photosynthetic pigments, lipid peroxidation, and accumulation of
inorganic ions in barley plants under the action of cadmium chloride
was studied. It was shown for the first time that the protective
effect of phytomelatonin during short-term treatment is manifested in
a decrease in the toxic effect of cadmium on the content of
photosynthetic pigments and the accumulation of cadmium ions in the
shoots and roots of barley plants. The protective effect of melatonin
is based on its ability to reduce the intensity of oxidative stress by
maintaining the level of carotenoids and increasing the activity of
antioxidant enzymes. The effectiveness of short-term use of melatonin
in a number of indicators exceeds its protective effect from long-term
exposure. The data obtained indicate the possibility of using
melatonin as a substance that induces the state of plant priming upon
subsequent exposure to cadmium.

Under the conditions of a growing experiment, the authors studied the effect of zinc at concentra_x0002_tions of 5 (control), 50, 100, and 150 mg/kg substrate on growth, the intensity of lipid peroxidation (LPO), and the activity of the components of the antioxidant system in Brassica juncea L. (Сzern.) variety Slavyanka and Sinapis alba L. cultivar Belgium plants. Some differences and similarities were found in the AOS response of the studied species to an excess of zinc in the root environment. Thus, there were no changes in the inten_x0002_sity of lipid peroxidation in B. juncea under the influence of zinc in high concentrations, despite the high con_x0002_tent of the metal in the roots and shoots. At the same time, even in the presence of metal at a concentration of 50 mg/kg substrate, an increase in the activity of guaiacol peroxidase (GPX) and catalase was observed. In S. alba at high concentrations of zinc in the substrate, the metal content in the shoots was higher than in B. juncea. At the same time, the content of malondialdehyde noticeably increased, despite the increased activity of superoxide dismutase and GPX. In both studied plant species, an increase in the zinc concentra_x0002_tion in the substrate to 50 mg/kg and above led to an increase in the level of proline, while the content of carotenoids decreased. Considering that, in the studied concentrations, the metal had a less strong negative effect on shoot growth in B. juncea compared with S. alba, it was concluded that plants of this species are more resistant to excess zinc in the root environment.

The effect of 1 M NaCl on the lipid profile of detergent-resistant chloroplast membranes was studied. sts and mitochondria of salt-accumulating halophyte plants – Salicornia perennans Willd. And Suaeda salsa (L.) Pall. (family Amaranthaceae). The composition of lipids and fatty acids in detergent-resistant membranes differs from the membrane lipids of chloroplasts and mitochondria by a large number of cerebrosides and sterols. Under the given salinity conditions, S. perennans experienced many a fold increase in the proportion of cerebrosides in the composition of detergent-resistant chloroplast membranes, and in S. salsa is found in detergent-resistant mitochondrial membranes. The opposite effect was observed in relation to sterols: a decrease in their relative content under the action of salt. Received data indicate the participation of detergent-resistant membranes in the interaction of chloroplast cells and mitochondria in the cellular response of halophytes to salinity.

Pretreatment of roots with salicylic acid (SA) and its role in control over morphophysiological parameters characterizing cold resistance of plant regenerants were examined in potato (Solanum tuberosum L.). It was found that potato plants exposed to low above-zero temperatures (4°C, 3 days) failed to restore initial growth parameters (plant height, leaf surface area, number of stolons, and weight of the organs) and oxidative status (intensity of lipid peroxidation) of the roots and leaves after transfer to favorable conditions (22°C, 10 days). A short-term (4-h-long) pretreatment of the roots with 0.1 μM SA minimized the adverse effect of deferred chilling. SA treatment promoted restoration of the initial plant phenotype after hypothermia, which caused a rise in growth parameters (number and surface area of the leaves and number of stolons) as compared with plants exposed to chilling without SA treatment. It was shown that pretreatment with SA improves cold resistance of potato plants owing to changes in the activity of antioxidant enzymes (superoxide dismutase and guaiacol-dependent peroxidase) and in the level of nonenzymatic antioxidants (ascorbic acid, anthocyans, total flavonoids and phenolic compounds). Depending on conditions, SA alters the ratio between individual flavonoids in the leaf. An ambiguous response to chilling and SA treatment was observed in two lines of potato regenerants produced by means of in vitro microcloning from the apical and middle part of the shoot, which is probably associated with their differing hormonal status.