Effects of Silicon Nanoparticles on the Activity of Antioxidant Enzymes in Tomato Roots Invaded by Meloidogyne incognita (Kofoid et White, 1919) Chitwood, 1949.

The effect of silicon nanoparticles (1 µg/mL) on the activity of lipid peroxidation, peroxidase, superoxide dismutase, and catalase in tomato roots invaded by root-knot nematode Meloidogyne incognita was studied. It was shown that, at the early stages of parasitization in the plants treated with Si-NPs, a low activity of PO and SOD, as well as an increased level of lipid peroxidation, are observed, which indicates the formation of free radicals (reactive oxygen species, ROS) that can inhibit nematodes and limit the formation of giant cells. During the sedentary stage, at the stages of nutrition, development, and egg production, the roots of the treated plants showed an increased activity of PO, CAT, and SOD, as well as a low activity of LPO as compared to the infested untreated plants. This makes it possible to maintain a balance between the formation and neutralization of ROS and is important not only in the protection of plant tissues from oxidative processes but also in the preservation of giant cells that feed the parasite. The presented data for the first time show the mechanism of action of Si-NPs in the development of resistance and adaptation of plants to biogenic stress, associated with the effect on various components of the antioxidant system and their functional interaction.

Effects of Silicon Nanoparticles on Photosynthetic Pigments and Biogenic Elements in Tomato Plants Infected with Root-Knot Nematode Meloidogyne incognita.

New data on the effect of colloidal silicon nanoparticles on the content of nutrients and photosynthetic pigments in tomato plants invaded by root-knot nematode Meloidogyne incognita are presented. Foliar treatment of plants with colloidal solutions of silicon nanoparticles at concentrations of 0.5 and 1.0 µg/mL revealed an increase in the content of photosynthetic pigments and a number of biogenic elements (P, Mg, K, S, and Fe) in tomato leaves, indicating an improvement in the physiological state of the invaded plants. The stimulating effect of nanosilicon on the development and growth of plants and the inhibiting effect on the susceptibility of plants by nematodes and the morpho-physiological parameters of the parasite is shown.

Effect of Salicylic Acid on the Oxidative and Photosynthetic Processes in Tomato Plants at Invasion with Root-Knot Nematode Meloidogyne incognita (Kofoid Et White, 1919) Chitwood, 1949.

A study of the processes of lipid peroxidation and the activity of the peroxidase enzyme, as well as photosynthetic pigments in susceptible tomato plants treated with salicylic acid (SA), during infection with the root-knot nematode Meloidogyneincognita. It was shown that, in the roots of SA-treated plants, the activity of lipid peroxidation is higher compared to the untreated plants, especially in the case of nematode invasion. A significant increase in the activity of lipid peroxidation in SA-treated invasive plants compared with untreated was noted during the transition of larvae to the sedentary stage and the beginning of the formation of feeding areas-giant cells (3-5 days after invasion). This, apparently, contributes to the inhibition of the development of the parasite and the reduction of plant infection and also indicates the involvement of oxidative processes in the mechanism of the induced resistance of plants to root-knot nematodes. In the SA-treated plants, the qualitative and quantitative composition of photosynthetic pigments, disturbed by invasion, was restored and corresponded to the control level.

Selenium Nanoparticles-an Inducer of Tomato Resistance to the Root-Knot Nematode Meloidogyne incognita (Kofoid et White, 1919) Chitwood 1949.

We investigated the mechanisms of action of selenium nanoparticles obtained by laser ablation for their use as an abiogenic elicitor of tomato resistance to parasitic nematodes. Selenium nanoparticles induced systemic resistance of tomatoes to the root-knot nematode, stimulated plant growth and development, was involved in the PR-6 gene expression in the roots and leaves of plants subjected to invasion, and increased the activity of proteinase inhibitors (markers of systemic resistance of plants to infection). Exogenous treatment of plants with solutions of selenium nanoparticles reduced the invasion of plants by affecting the morphological and physiological parameters of the parasites in the roots.

Activity of components of the antioxidant system in the roots of potato plants at short-term temperature drop and invasion with parasitic nematodes.

The activity of catalase and superoxide dismutase in the roots of susceptible plants and plants exposed to alternating temperatures, which were infected with the phytoparasitic nematode G. rostochiensis, was studied. It was found that, throughout the invasion period, the plants susceptible to invasion exhibited a high activity of these enzymes, which allowed them to maintain an active defense against the oxidative stress caused by the invasion and subsequent life activity of larvae. For the plants exposed to alternating temperatures, a decrease in the activity of catalase and superoxide dismutase at the early stages of invasion and an increase in the activity of these enzymes at the later stages was detected.

Expression of PR genes in tomato tissues infected by nematode Meloidogyne incognita (Kofoid et White, 1919) Chitwood, 1949.

The dynamics of expression of PR1 and PR6 genes, which are involved in the defense response of plants infected with the root-knot nematode Meloidogyne incognita, was studied in the "tomato-root-knot nematode" parasitic system. The invasion of the resistant plants was accompanied by an increased accumulation of transcripts of PR genes, which reflects their fast response to the penetration of nematode juveniles with subsequent development of an adequate defense response. In the susceptible plants, changes in the PR1 and PR6 gene activity induced by the nematode invasion were insignificant, which may be one of the causes of the disease. An exogenous salicylic acid treatment of the susceptible plants increased the PR1 and PR6 genes activity and led to the development of resistance of these plants to nematode invasion.

Mi-1 gene expression in tomato plants under root-knot nematode invasion and treatment with salicylic acid.

The dynamics of expression of two homologous genes Mi-1.1 and Mi-1.2 in the roots of resistant and susceptible tomato plants in non-invasion conditions and during invasion with the root-knot nematode M. incognita was studied. Nematode invasion was accompanied by a significant increase in the expression level of both genes; however, the accumulation of transcripts at the early stages of nematode invasion in the penetration of nematode juveniles to the roots was observed only in plants that contained the Mi-1.2 gene, which explains the resistance of tomatoes to this root-knot nematode, caused by only this gene. We reveal a change in the Mi-1 gene activity under exogenous salicylic acid treatment, which contributed to the formation of induced resistance to root-knot nematode in the susceptible plants.

Pine Wilt Disease and Possible Causes of Its Incidence in Russia.

Surveys of forests and stockpiled timber of pine, spruce, larch, and silver fir in 14 administrative subjects of the Russian Federation revealed widespread occurrence of the coniferous wood parasitic nematode Bursaphelenchus mucronatus. Twenty species of bacteria belonging to 13 genera have been detected in 25 B. mucronatus isolates, and their identity has been determined by direct sequencing of the 16S- RNA gene. The most frequently occurring were bacteria from the genera Pseudomonas, -Stenotrophomonas, Pantoea, Bacillus, Burkholderia, and Serratia. Prevalence of Pseudomonas brenneri and P. fluorescence, which were also found in the nematode dauer larva (Liv) isolated from the fir sawyer beetle Monochamus urussovi, have also been assessed. Two nematode B. xylophilus isolates from Portugal and one isolate from the United States have been examined, and 10 symbiotic bacteria species have been isolated, including Agrobacterium tumefacience, P.fluorescens, P. brenneri, Rahnella aquatilis, Stenotrophomonas maltophilia, S. rhizophila, and Yersinia mollaretfi.

The expression of R genes in genetic and induced resistance to potato cyst nematode Globodera rostochiensis (Wollenweber, 1923) Behrens, 1975.

The characteristics of expression of two genes, H1 and Gro1-4, which determine the resistance to the sedentary parasitic nematode Globodera rostochiensis (Wollenweber, 1923) Behrens, 1975, in the resistant (Krepysh) and susceptible (Nevskii) potato cultivars was studied under a short-term exposure to low temperatures. Such treatment of susceptible plants at the early stages of ontogeny led to the activation of expression of H1 and Gro1-4 genes in roots and the H1 gene in leaves. The transcriptional activity of R genes was detected not only in roots but also in leaves (i.e., in tissue remote from the site of direct injury by the nematode) in the case of both genetic and induced resistance, indicating the development of a systemic defense response of plants to infection.

[World Collections of Parasitic Worms].

This article provides information about the depositories of parasitic worms in the scientific institutes and museums in the United States, Japan, and Europe (the total number of samples and the availability of types of helminths from various classes), as well as information on the availability of electronic catalogues of the collections in the continental, national, and regional centers for collective use. The extent of this material has determined the necessity of creating digital collections and libraries that would represent a new form of storing, displaying, and exchanging information for scientific research. An analysis was performed of the current state of approaches and methods of development of the specialized information retrieval system (IRS) and databases (DBs) on the parasitic worms in Russia on the basis of a common conceptual data model, taking into account their local use (as desktop systems of database management) and access by scientists worldwide via the Internet.

Co-adaptation mechanisms in plant-nematode systems.

The review is aimed to analyze the biochemical and immune-breaking adaptive mechanisms established in evolution of plant parasitic nematodes. Plant parasitic nematodes are obligate, biotrophic pathogens of numerous plant species. These organisms cause dramatic changes in the morphology and physiology of their hosts. The group of sedentary nematodes which are among the most damaging plant-parasitic nematodes cause the formation of special organs called nematode feeding sites in the root tissue called syncytium (cyst nematodes, CN; Heterodera and Globodera spp.) or giant cells (root-knot nematodes, RKN; Meloidogyne spp.). The most pronounced morphological adaptations of nematodes for plant parasitism include a hollow, protrusible stylet (feeding spear) connected to three esophageal gland cells that express products secreted into plant tissues through the stylet. Several gene products secreted by the nematode during parasitism have been identified. The current battery of candidate parasitism proteins secreted by nematodes to modify plant tissues for parasitism includes cell-wall-modifying enzymes, multiple regulators of host cell cycle and metabolism, proteins that can localize near the plant cell nucleus, potential suppressors of host defense, and mimics of plant molecules. Plants are usually able to recognize and react to parasites by activating various defense responses. When the response of the plant is too weak or too late, a successful infection (compatible interaction) will result. A rapid and strong defense response (e. g. due to the presence of a resistance gene) will result in the resistant (incompatible) reaction. Defense responses include the production of toxic oxygen radicals and systemic signaling compounds as well as the activation of defense genes that lead to the production of structural barriers or other toxins.