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Etiology

Soft Rot of Crisphead Lettuce Incited by Erwinia carotovora subsp. carotovora in Hawaii. J. J. Cho, Associate plant pathologist, Department of Plant Pathology, University of Hawaii, HITAHR, Maui Branch, P.O. Box 269, Kula 96790; Phytopathology 73:1206-1209. Accepted for publication 28 April 1983. Copyright 1983 The American Phytopathological Society. DOI: 10.1094/Phyto-73-1206.

Erwinia spp. pathogenic in lettuce were isolated from 120 samples of diseased crisphead lettuce. Frequency of recovery ranged from 96.7 to 100%. Ten isolates were similar to Erwinia carotovora subsp. carotovora when compared in biochemical and pathological tests with known strains. A typical soft rot isolate from lettuce was compared with a known strain of E. carotovora subsp. carotovora (EC105) with respect to pathogenicity to a susceptible and resistant lettuce cultivar. In both cultivars, extensive maceration occurred 2 days after inoculation in the pith region of mature plants. Differences in the amount of rot were observed in relation to bacterial strain and cultivar when the midribs of wrapper leaves were inoculated. Multiplication of a lettuce soft rot strain was similar in the leaf midribs of a resistant as compared with a susceptible lettuce cultivar; however, maceration occurred earlier and at lower population levels in the latter.