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Identification and Host Range of an Erwinia Pathogen Causing Stem Rots on Hydroponically Grown Plants. Andrew C. Schuerger, Senior Plant Pathologist, The Land, EPCOT Center, P.O. Box 10000, Lake Buena Vista, FL 32830. Jean Carlson Batzer, Technical Specialist, The Land, EPCOT Center, P.O. Box 10000, Lake Buena Vista, FL 32830. Plant Dis. 77:472-477. Accepted for publication 21 December 1992. Copyright 1993 The American Phytopathological Society. DOI: 10.1094/PD-77-0472.

A bacterium pathogen causing stem rot and vascular wilt symptoms on hydroponically grown vegetables was identified by biochemical tests and cellular fatty acid compositions as Erwinia carotovora subsp. carotovora. Eighteen different plant hosts were screened for resistance to the pathogen. Stems of hydroponically grown plants were inoculated (with a micropipette technique) with 100-μl bacterium suspensions at several dosage levels between 3.4 × 104 and 3.4 × 108 cfu/ml. Pole bean (Phaseolus vulgaris ‘Glastada’), Chinese bitter melon (Momordica charantia ‘Park 5188’), and luffa gourd (Luffa aegyptiaca) were the most resistant; plants failed to develop stem rot or wilt symptoms at any of the dosage levels tested. Potato (Solanum tuberosum ‘Russet Burbank’) and tomato (Lycopersicon esculentum ‘N-65’) were classified as moderately resistant because inoculated tissues developed rot symptoms at dosage levels of 106 and 108 cfu/ml, but not at 104 cfu/ml. Winter squash (Cucurbita maxima ‘Banana Pink Jumbo’), pepper (Capsicum annuum ‘Early Thickset’), buffalo gourd (Cucurbita foetidissima ‘Az. Synthesis 1’), tobacco (Nicotiana tabacum ‘Coker 48’), and cucumber (Cucumis sativus ‘Vetomil’) were rated as moderately susceptible because stem rot symptoms occurred on 10–50% of the plants inoculated at the 104-cfu/ml dosage level. Plants within the Cruciferae and cantaloupe (Cucumis melo ‘Chilton’) were the most susceptible; stem rot symptoms were observed within 3 days after inoculation on at least 50% of the plants inoculated at the lowest dosage level of 3.4 × 104 cfu/ml. Horticultural activities that increased wounding of plants generally increased the incidence of disease.

Keyword(s): aeroponic, API 20E.