Abstract—
Nine strains of Pectobacterium atrosepticum (Pca) were analyzed in this work, and new information about the pathogen properties and regulation of its main virulence factors was obtained. In exopolysaccharides (EPS) of Pca, anionic groups ( \({\text{PO}}_{4}^{{3 - }}\) ) were detected, the amount of which varied in different strains and probably contributed to the formation of denser biofilms. Most Pca strains inhibited to varying degrees the growth of potato plants in vitro; however, one of them (426) activated significantly the growth of the plants of the resistant potato variety Lugovskoi. Based on the totality of the disease symptoms (chlorosis, necrosis, wilt, inhibition of growth rate), all P. atrosepticum strains were divided by the degree of virulence. In addition, it was demonstrated that the incubation of bacteria with homogenate from potato plants in vitro modulated the activity of pectinase in Pca homogenate from the plants of the resistant potato variety Lugovskoi inhibited the activity of exopectinase, while that from the susceptible variety Lukyanovskii activated it. At the same time, the activity of exopectinase from the avirulent strain 426 was inhibited to the greatest extent. It is assumed that this was a reason for the stimulation of the growth of the resistant potato variety plants in vitro.
