REINFECTION OF Y-VIRUS ON SEED POTATO IN THE MIDDLE VOLGA

The studies were carried out to identify the relationship between the vector activity of aphids and the intensity of Y-virus reinfection on seed potatoes. The growth rate of viral infection was assessed using the reinfection coefficient, which is the ratio between the rates of infection at the end and beginning of the growing season. The vector activity of aphids was determined for the entire growing season, taking into account the severity coefficients for different aphid species. The critical threshold for the vector activity of aphids was considered to be the abundance level equivalent to 50 specimens of the peach aphid. With the vector activity of aphids at the level of the critical threshold (1 CT), the coefficient of reinfection PVY of Nevskiy variety was at the level of 1. When it increased to 2.6 times the critical threshold, a 3.8… 4.8-fold increase in the coefficient of reinfection occurred. With a further increase in the vector activity of aphids to 4.3 and 10.5 critical threshold, it remained at the same level. The inhibition of the growth of critical threshold is explained by the fact that the Y-virus, as not persistent, remains in the carrier for a short time and therefore is transmitted to the same nearby surrounding plants. The accumulation of viral infection in the early stages of reproduction of the original and original material can occur latently, which is associated with a limited number of samples taken for analysis (200 ... 250 plants or tubers) and, accordingly, a low probability of detecting the degree of infection less than 0.5%. According to the results of calculations during the reproduction of seed with a reinfection coefficient of 4 and reaching the first reproduction with an infestation of 10%, the safe level of infestation of PVY in greenhouse minitubers should not exceed 0.01%, in the first field generation - 0.04%, in the super-super-elite - 0 , 15%, among the super elite - 0.6%, the elite - 2.5%