E. M. Matveeva

Expression of genes, encoded defense proteins, in potato plants infected with the cyst-forming nematode Globodera rostochiensis (Wollenweber 1923) Behrens, 1975 and modulation of their activity during short-term exposure to low temperatures

The expression of the principal genes providing an immune response in the roots of potato plants resistant and susceptible to the cyst nematode Globodera rostochiensis is investigated under conditions of infestation and with frequent variations in temperature. Differences in the immune status of resistant and susceptible potato cultivars are revealed in the level of expression of R-genes (H1 and Gro1-4), gene PAL, and defense genes of the PR-family (PR1, PR2, PR3, PR6). Varying the temperature changes the activity of transcriptome of susceptible plants towards activation of expression of R-genes, gene PAL, and defense genes; interactions between the plant and parasite are displaced towards induction of host resistance.

Characteristics of soil nematode communities under conditions of woody plant introduction

Nematode communities in the rooted soil layer under the crowns of introduced tree species on Valaam Island (Republic of Karelia) have been studied by conventional nematological methods to evaluate their taxonomic diversity, population density, and eco-trophic structure. On the whole, 49 nematode genera have been recorded, with their total abundance varying from 1209 to 2548 ind./100 g soil. The abundance and proportion of plant parasites in the soil nematode assemblage have proved to be higher under introduced trees, compared to natural forest biocenoses.

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.

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.

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.

Сообщества почвенных нематод агроценозов с монокультурами (на примере Республики Карелия)

The effect of crops cultivation on the soil free-living and plant-parasitic nematodes in agrocenoses of southern Karelia (fields with tilled crops, artificial grasslands) was studied. A comparison of monodominant plant communities in agrocenoses (tilled crops) and cenoses with alien species Heracleum sosnowskyi Manden was made. The characteristics reflecting the features of nematode communities in different types of agrocenoses were established. They include faunal composition with identification of constant and specific taxa determining the similarity/differences between agrocenoses, trophic structure of nematode communities, and ecological and population indices facilitating the assessment of soil ecosystem state. Bacterial and fungal feeders resistant to unfavourable conditions dominate under tilled crops and take part in organic matter decomposition, forming the core of the nematode fauna. In seeded meadows plant feeder nematodes become more significant in the community. The values of ecological and population indices show that the soil ecosystem is structured and stable. According to the characteristics of soil nematode communities the agroecosystem of the polycomponent seeded meadow corresponds to a late stage of ecological succession.

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.