Comparison Of Temperature Effects On The In Vitro Growth And Disease Development In Potato Tubers Inoculated With Bacteria Pectobacterium Atrosepticum, P Carotovorum Subsp Carotovorum And Dickeya Solani

The relationship between the rate of in vitro growth of bacterial isolates of Pectobacterium atrosepticum, P. carotovorum subsp. carotovorum and Dickeys solani and their pathogenicity was investigated in tubers of two potato cultivars at four temperatures ranging from 18 degrees C to 30 degrees C. The rate of in vitro growth was highly positively correlated with the number of rotted tubers (r ranged from 0.91 to 0.93) and with the weight of macerated potato tissue, which, however, was only found for P. carotovorum and D. solani (r = 0.76; r = 0.91, respectively) and not for P. atrosepticum. The weight of macerated tissue increased with the temperature, but significant differences between species of bacteria were observed only at 26 degrees C and above, at which temperatures D. solani was the most aggressive, followed by P. carotovorum and P. atrosepticum. Almost all potato tubers inoculated with bacteria showed symptoms of soft rot at 26 degrees C and 30 degrees C, but the number of rotting tubers at lower temperatures (22 degrees C and 18 degrees C) decreased significantly. The lowest disease incidence, 11% of tubers with symptoms, was observed for the D. solani and cultivar Sonda at 18 degrees C, what was also confirmed in a separate experiment with tubers from four potato cultivars inoculated with the highly aggressive isolate of D. solani. At temperatures from 18 degrees C to 30 degrees C, the differences in disease severity between potato cultivars with various resistance to bacteria increased in line with temperature, while the differences in disease incidence decreased.