Comparative Injuriousness to Plants of Erwinia spp. and Other Enterobacteria from Plants and Animals

Summary. To determine their degree of injuriousness to plants, 148 cultures of Erwinia and other enterobacteria, including 45 ‘ Erwinia ‐like’ isolates from animals, were examined comparatively by tests for hypersensitivity reaction, stalk rot and leaf blanching of corn seedlings, lesions on excised bean pods and on cowpea seedlings, rots of excised plant tissues and liquefaction of carboxymethylcellulose and pectate gels. The degree of harmfulness could be expressed as a standardized Erwinia injuriousness score calculated from numerical expressions of symptoms produced by a culture on cowpea seedlings compared with those produced by two reference cultures known to be phytopathogenic and, hence, injurious. The results indicate that, of the 45 Erwinia ‐like isolates from animals tested, 16 were not injurious to plants, 13 were only slightly injurious, and 16 were as injurious to certain test plants as some Erwinia strains generally considered to be phytopathogenic.