Comparison of the blossom and shoot susceptibility of European and Asian pear cultivars to Pseudomonas syringae pv. syringae

The susceptibility of 14 pear cultivars to the bacterium Pseudomonas syringae pv. syringae, the causal agent of bacterial blast, was evaluated using three different methods of in vivo inoculation detached shoots inoculation in a growth chamber, and terminal shoot and blossom inoculation of potted trees in a net house in the period 2020-2022. The 20-week assessment of infection symptoms in the net house showed different dynamics of disease development depending on the inoculation method, the weather during the growing season and the susceptibility of the pear cultivars. Most of the cultivars were during the study low susceptible to pathogen and were classified in blossom, terminal as well as detached shoot susceptibility class 2. The European cultivar Kiefer was the least susceptible (susceptibility class 1) to blossom infection, the Asian cultivars Chojuro and Ya Li to terminal shoot infection, and Ya Li to detached shoot infection. The European cultivar William's was the most susceptible to all types of infection, being classified in class 3, moderately susceptible cultivars to infection of terminal shoots, and class 4, highly susceptible cultivars to infection of blossoms and detached shoots. The assessment of susceptibility of pear cultivars to Pseudomonas syringae pv. syringae in the net house approximated conditions as close as possible to the condition in orchards and should thus be consistent in plantings with similar environmental and weather conditions.