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Etiology

A Bacterial Wilt and Root Rot of Sweet Potato Caused by Erwinia chrysanthemi. N. W. Schaad, Assistant Professor, Department of Plant Pathology, University of Georgia, Georgia Experiment Station, Experiment, GA 30212; D. Brenner, Chief, Enteric Section, Enterobacteriology Branch, Bacteriology Division, Center for Disease Control, Public Health Service, Department of Health, Education and Welfare, Atlanta, GA 30033. Phytopathology 67:302-308. Accepted for publication 7 September 1976. Copyright © 1977 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-67-302.

Erwinia chrysanthemi has been identified as the cause of a severe wilt and root rot of sweet potato in Georgia. The susceptibility of 14 sweet potato cultivars ranged from the highly resistant Red Jewel to the highly susceptible Georgia Red and Georgia Red 85. Several other plants including chrysanthemum, daisy, tobacco, pepper, tomato, Irish potato, cabbage, eggplant, soybean, petunia, African violet, morning-glory, and Cuscuta sp. also were susceptible. Erwinia chrysanthemi was isolated from soil and soil debris collected from a harvester, but not from field soil. Of 56 apparently healthy roots collected from a harvester and placed at 32 C in polyethylene bags, 23 were rotted by the bacterium. Seven biochemical tests (malonate, indole, lecithinase, phosphatase, litmus milk, lactose, and maltose) were highly reliable for distinguishing E. chrysanthemi from other species of Erwinia. Deoxyribonucleic acid from the sweet potato bacterium exhibited an average 80% relatedness to E. chrysanthemi as compared to less than 30% relatedness to E. carotovora.