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An Improved Method for the Inoculation of Corn with Erwinia spp.. John R. Hartman, Research Assistant, Department of Plant Pathology, University of Wisconsin, Madison 53706, Present address of senior author: University of Kentucky, Lexington 40506; Arthur Kelman, Professor, Department of Plant Pathology, University of Wisconsin, Madison 53706. Phytopathology 63:658-663. Accepted for publication 8 December 1972. DOI: 10.1094/Phyto-63-658.

Infection of corn plants using a whorl inoculation method with 0.7% Tween 40 and a corn pathotype of Erwinia chrysanthemi (ECZ) (5 × 107/ml) resulted in consistent rotting and collapsing of 3-week-old corn plants about 48 hr after inoculation. Most other inoculation techniques, including stem injections, were erratic or not successful under greenhouse or growth room conditions. In field tests, Tween 40 also enhanced infection and development of stalk rot of sweet corn and field corn following whorl inoculation with ECZ. Using this improved technique, ECZ isolates from North Carolina, Wisconsin, Egypt, and India were pathogenic to corn; whereas E. carotovora, E. atroseptica, and E. aroideae isolates were not. Erwinia chrysanthemi appeared to be weakly virulent to corn in certain tests. An initial decrease (fivefold after 10 hr) in population of ECZ in inoculated plants was followed by a rapid increase in cells (100-fold after 36 hr) paralleling appearance of initial internal symptoms of stalk rot. In contrast, E. carotovora populations declined 20-fold during the entire 48-hr observation period.

Additional keywords: Tween 80, Tween 20, Eosin Y.