Relevance. Oxidative reactions (based on peroxidase activity, POX and polyphenol oxidase, PPO; hydrogen peroxide content) that occur in response to infection or reinfection of the off-spring of infected plants depend on the type of host-virus interaction (sensitive, tolerant, stable) and the nature of the interaction with viral infection (primary infection, reinfection of second and third generations).Results. Reinfection with tomato aspermy virus (TАV) or tobacco mosaic virus (TMV) of the off-spring of third infected tomato generation caused a significant decrease in POX activity compared to successive generations of infected plants (G2) for Craigella (Tm-22/Tm- 22) and S. pimpinellifolium genotypes or an increase for Rufina and Craigella (Tm-1/Tm-1) ones. In genotypes containing resistance genes, Rufina and Craigella, no differences were observed in PPO of TMV primary infection and control, while significant differences were found in case of TAV (susceptibility). As a result of TMV infection, the sensitive (Elvira) and tolerant (S. pimpinellifolium) genotypes showed an increase in PPO values compared to the control. At the same time, in most genotypes primarily / secondarily infected with TAV or TMV, statistically significant differences were revealed in the activity of POX or PPO, as well as the accumulation of hydrogen peroxide in plant leaves, which indicates specific protective reactions of the genotypes.

Relevance. One of the most important factors which can influence on the growth and development of strawberries is the negative temperature in winter and especially in its snowless period. We were interested to study special aspects of the oxidative stress, accumulation of protector’s conjunctions, antioxidant and water status in autumn period of varieties strawberry garden different ecologicalgeographical origin in the conditions of the Orel region.Methods. The objects of the research were the leaves of Fragaria ananassa of different ecological and geographical origin in autumn period: Tsaritsa, Alba, Sara, Korona, Kokinskaya Rannya, Solovushka, Urozhainaya TsGL.Results. As the result was shown that in autumn period, when plants began preprocessing for winter, strawberry varieties Solovushka, Tsaritsa, Sara and Korona have been marked by increased antioxidant activity (for example, the enzymes SOD and catalase), little formation of reactive oxygen species and, in the end, low structural and functional damage to cell membranes. Also it was shown an increase in bound and a decrease in free water in the leaves of plants when the temperature decreased. At the same time, in the end of autumn, on the background of high content of free proline (19.38-29.73 mg/kg) and sucrose (2.65-6.46 mg/g), the varieties Solovushka, Tsaritsa, Sara and Korona had the highest ratio of bound/free water (4.10-8.10) in comparison with the with Urozhainaya TsGL and Alba. Thus, the varieties Solovushka, Tsaritsa, Sara and Korona are characterized by high adaptability to the winter conditions in the Orel region.