VIRULENCE ON CITRUS OF PSEUDOMONAS-SYRINGAE STRAINS THAT CONTROL POSTHARVEST GREEN MOLD OF CITRUS-FRUIT

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 str ains reduced postharvest green mold of lemons, caused by Penicillium d igitatum. Properties of strains studied included tobacco hypersensitiv e 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 cellul ar fatty acid analysis indicated ESC-10 was more closely related to 48 5-10 than was ESC-11. Shoots, leaves, and fruit of many cultivars were inoculated. Only strain 485-10 caused lesions on shoots and leaves, a nd large, sunken lesions an citrus fruit. ESC-10 caused darkening of w ounds on fruit while water or ESC-11 did not. Only on lime fruit did a ll three strains cause lesions after the application of 10(8) CFU/ml, although those caused by ESC-10 and ESC-11 were very small compared wi th those of 485-10. Pathogenicity was detected and virulence was quant ified faster by inoculation of lime fruit than by other methods. Strai ns 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 o n lime fruit.