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Virulence on Citrus of Pseudomonas syringae Strains that Control Postharvest Green Mold of Citrus Fruit. J. L. Smilanick, Horticultural Crops Research Laboratory, 2021 South Peach Avenue, Fresno, CA 93727. C. C. Gouin-Behe, University of Florida/USDA-ARS, Beltsville, MD 20705; D. A. Margosan and C. T. Bull, Horticultural Crops Research Laboratory, 2021 South Peach Avenue, Fresno, CA 93727; and B. E. Mackey, Biometrics Unit, USDA-ARS, 800 Buchanan Street, Albany, CA 94710. Plant Dis. 80:1123-1128. Accepted for publication 24 June 1996. 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, 1996. DOI: 10.1094/PD-80-1123.

To determine if their commercial use would entail significant risk of introducing pathogens to citrus, Pseudomonas syringae strains (ESC-10 and ESC-11) used for Postharvest biological control were compared with strain 485-10, which caused citrus black pit and blast. All three strains reduced Postharvest green mold of lemons, caused by Penicillium digitatum. Properties of strains studied included tobacco hypersensitive reactions (HR), carbohydrate utilization (Biolog GN), cellular fatty acid profiles, and virulence. HR of ESC-10 and 485-10 were positive, while that of ESC-11 was negative. Carbohydrate utilization and cellular fatty acid analysis indicated ESC-10 was more closely related to 485-10 than was ESC-11. Shoots, leaves, and fruit of many cultivars were inoculated. Only strain 485-10 caused lesions on shoots and leaves, and large, sunken lesions on citrus fruit. ESC-10 caused darkening of wounds on fruit while water or ESC-11 did not. Only on lime fruit did all three strains cause lesions after the application of 108 CFU/mi, although those caused by ESC-10 and ESC-11 were very small compared with those of 485-10. Pathogenicity was detected and virulence was quantified faster by inoculation of lime fruit than by other methods. Strains ESC-10 and ESC-11 do not pose a significant threat to citrus fruit, foliage, or shoots of all varieties tested, except for Persian lime, in which small lesions were observed after the inoculation of wounds on lime fruit.