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Postharvest Pathology and Mycotoxins

Diversity of Pectolytic, Fluorescent Pseudomonads Causing Soft Rots of Fresh Vegetables at Produce Markets. C. H. Liao, Research plant pathologists, Eastern Regional Research Center, Agricultural Research Services, U.S. Department of Agriculture, Philadelphia, PA 19118; J. M. Wells, Research plant pathologists, Eastern Regional Research Center, Agricultural Research Services, U.S. Department of Agriculture, Philadelphia, PA 19118. Phytopathology 77:673-677. Accepted for publication 2 October 1986. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1987. DOI: 10.1094/Phyto-77-673.

Pectolytic bacteria (128 strains) isolated from rotted specimens of 10 vegetables were characterized. Sixty-four strains (50%) were identified as Erwinia carotovora, 55 strains (43%) as fluorescent Pseudomonas spp., and the remaining nine strains (7%) as Bacillus sp., Cytophaga johnsonae, or Xanthomonas campestris. Fluorescent pseudomonads accounting for almost half of vegetable rots found at markets were divided into four groups based on six physiological tests. Each group was nutritionally heterogenous and could be divided into several (four to 11) subgroups according to their ability to use 10 out of 30 organic compounds tested as energy or carbon sources. Oxidase-positive strains (Groups 13) were similar to but did not exactly fit into the ideal phenotype of P. fluorescens biovar II, biovar IV, or biovar V. Oxidase-negative strains (Group-4) constituting 29% (16 strains) of the total pseudomonads isolated were closely related to P. viridiflava, but 11 strains were unable to induce hypersensitive response on tobacco and four strains unable to use sorbitol.

Additional keywords: Erwinia carotovora, postharvest decays, Pseudomonas fluorescens, P. marginalis, soft-rot bacteria.