We used the average proportion of current season’s shoot growth that was blighted to quantify a cultivar’s response to fire blight higher average values indicate higher susceptibility. In 20, we inoculated multiple actively-growing shoots per tree with a virulent strain of Erwinia amylovora (Figs. Cultivars on M.111 rootstocks were planted at WSU Columbia View Research Orchard. We determined fire blight resistance/susceptibility levels of 94 apple cultivars and important breeding parents through a two-year, replicated field inoculation study that focused on shoot infection. Several cultivars including Aurora Golden Gala, Empire, and Enterprise had moderately to highly resistant responses in both years.Although most cultivars are susceptible, fire blight symptoms can vary among cultivars.Cultivar responses were relatively consistent between years.Most cultivars had a susceptible response to fire blight in 2016 and/or 2017.Variation in cultivar response to fire blight between years demonstrates the importance of evaluating susceptibility in multiple field seasons. For a given cultivar, differences in fire blight responses between years could potentially be attributed to: (1) variable environmental conditions (2) differences in tree age and/or vigor between years and (3) inoculation of shoots that were terminating growth in one of the years. Honeycrisp, Pinova, Spartan) appeared highly or moderately susceptible in one year and moderately resistant in the other. For example, a cultivar that had a highly susceptible response in 2016 often had a highly susceptible response in 2017. Cultivar responses were relatively consistent between years. Aurora Golden Gala, Empire, and Enterprise were consistently moderately to highly resistant (Table 1). Of interest, WA 38 had more moderate responses in both years (Table 1). Granny Smith, Winter Banana) were consistently highly susceptible. Enterprise was the only cultivar that did not develop any fire blight symptoms in either year of the two-year study. However, the degree of susceptibility depended on the cultivar (Table 1). Most of the apple cultivars we tested were susceptible to fire blight (Table 1). Variation in fire blight susceptibility responses among cultivars (photo credits: S.
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