Comparison of temperature effects on the in vitro growth and disease development in potato tubers inoculated with bacteria <i>Pectobacterium atrosepticum</i>,<i> P carotovorum</i> subsp. <i>carotovorum</i> and <i>Dickeya solani</i>

Abstract

Abstract The relationship between the rate of in vitro growth of bacterial isolates of Pectobacterium atrosepticum , P. carotovorum subsp . carotovorum and Dickeya solani and their pathogenicity was investigated in tubers of two potato cultivars at four temperatures ranging from 18°C to 30°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°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°C and 30°C, but the number of rotting tubers at lower temperatures (22°C and 18°C) decreased significantly. The lowest disease incidence, 11% of tubers with symptoms, was observed for the D. solani and cultivar Sonda at 18°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°C to 30°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.