VIEW ARTICLE

Postharvest Pathology and Mycotoxins

Association of Pectolytic Strains of Xanthomonas campestris with Soft Rots of Fruits and Vegetables at Retail Markets. C. H. Liao, Research plant pathologists, Agricultural Research Service/USDA, Postharvest Pathology Center, Rutgers University, New Brunswick, NJ 08903; J. M. Wells, Research plant pathologists, Agricultural Research Service/USDA, Postharvest Pathology Center, Rutgers University, New Brunswick, NJ 08903. Phytopathology 77:418-422. Accepted for publication 18 July 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-77-418.

Five strains of pectolytic, yellow-pigmented bacteria were isolated from rotted specimens of tomato, bell pepper, cucumber, and papaya collected at retail markets. The bacteria possessed cultural, morphological, and physiological properties conforming to those of Xanthomonas campestris. Each of the five strains obtained was capable of causing soft rots of detached plant parts of eight different crops (including potato tubers, carrot roots, celery petioles, cauliflower and broccoli curds, and fruits of cucumber, bell pepper, and tomato). The pathogenicity of each strain to plants (tobacco, cucumber, bell pepper, cabbage, and tomato) grown in the greenhouse could not be conclusively determined. These soft-rotting xanthomonads might represent an unusual cluster of X. campestris that exclusively attack plant materials after harvest and cause only soft rot symptoms. The tomato isolate excreted pectate lyase, pectin esterase, and polygalacturonase in medium containing polygalacturonic acid or pectin but not in a medium containing glucose. Two strains of X. campestris pv. campestris also produced extracellular enzymes in pectate media and were capable of causing mild rots of potato slices and other plant parts. This study provides the first experimental results indicating that some postharvest rots of plant crops may be attributed to pectolytic xanthomonads.