ISHS Acta Horticulturae 489: VIII International Workshop on Fire Blight
WATER RELATIONS AND INFECTION BY ERWINIA AMYLOVORA BASED ON CRAB APPLE BLOSSOM MODEL |
| Author: | P.L. Pusey |
| Abstract:
The effect of water on the interaction between Erwinia amylovora and flower tissue or nectar was studied using crab apple as an experimental model. Detached flowers were maintained at 24°C with the peduncle submerged in a sucrose solution. In one test, 0.1–0.2 μl of inoculum suspension (107 CFU/ml) was applied to stigmas of flowers held in 10% sucrose. After 24 h at 85 % relative humidity (RH), stigmas were wetted with 15 μl of water that flowed over the stigmas and into the floral cup (hypanthium). Flowers were held at 100% RH before drying and returning to 85% RH. After 1 week, only flowers subjected to wetting were diseased, and incidence was 90 to 100% regardless of whether drying occurred immediately or 48 h after wetting. In another experiment, 0.5 μl of an inoculum suspension (108 CFU/ml) was added directly to the hypanthium and RH ranged from 40 to 100%. In a third test, RH was held at 85 or 100% and sucrose in flower-holding vials was varied from 0 to 25%. Interrelationships of nectar volume, nectar water potential, nectar sugar concentration and population size of E. amylovora were consistent with early reports. The study also established a relationship between water potential in blossoms and blossom infection caused by E. amylovora. A determination of the full relevancy of results with detached flowers will require further research involving intact plants. | |
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