Publications - Faculty - Recently Submitted Faculty Publications 2008
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Dewdney - Phytopathology
Colonization and population growth of Erwinia amylovora on the apple stigma surface at cool temperatures.
Dewdney, M. M., Seem, R. C., Kim, W.-S., Svircev, A. M., and Aldwinckle
Abstract. Cool temperature (below 17.8°C) effects on epiphytic Erwinia amylovora populations on the apple stigma have never been fully described. Five apple cultivars Cameo, Gingergold, Royal Cortland, Rogers Red McIntosh, and Ace Spur Delicious were inoculated with three strains of E. amylovora (Ea 273, Ea 321, Ea 4001a) and phosphate buffer as a control at three constant temperatures (11, 18, and 25°C). There were five trees per cultivar in each temperature treatment and the strains were inoculated on separate branches of the trees. Blossoms were collected over a 3-day period and the populations of bacteria were quantified with real-time PCR and a Taqman probe. The experiment was conducted three times. The data were analyzed as a repeated measures experiment as both incidence and population data. Temperature was recorded throughout the experiment and was used to calculate degree-hour accumulations. Temperature, cultivar, strain of E. amylovora, day after inoculation, and the temperature x day after inoculation interaction all had significant (P< 0.05) effects on the colonization of the apple stigma surface. When the colonization data were fitted with cumulative degree-hours, the best base was determined to be 10°C. Cultivar no longer had a significant effect on colonization, but strain of E. amylovora, day after inoculation, and the interaction cultivar x cumulative degree-hours had a significant effect (P < 0.05). When compared to nine other models, the model that best described the population included the three-way interaction of temperature x cultivar x day after inoculation. The main effects of temperature, strain of E. amylovora and day after inoculation were all significant, but cultivar was not (P< 0.05). The best model based on cumulative degree-hours for population had the significant main effects (P< 0.05) of cumulative degree-hours (base 5°C) and strain of E. amylovora.
