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United States Department of Agriculture

Agricultural Research Service

Research Project: DOMESTIC, EXOTIC, AND EMERGING DISEASES OF CITRUS, VEGETABLES, AND ORNAMENTALS (DEED) Title: Dispersal of Xanthomonas citri subsp. citri bacteria downwind from harvested, infected fruit

Authors
item Parker, P.E. -
item Bock, C. H. -
item Cook, A.Z. -
item Gottwald, Timothy

Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 6, 2008
Publication Date: July 2, 2008
Citation: Parker, P., Bock, C., Cook, A., Gottwald, T.R. 2008. Dispersal of Xanthomonas citri subsp. citri bacteria downwind from harvested, infected fruit. Phytopathology. 98:S121

Interpretive Summary: Citrus canker (Xanthomonas axonopodis pv. citri , Xac) is a bacterial disease that severely damages citrus crops. Its recent introduction to Florida has created difficulties with international and domestic trade and movement of citrus material. This study examined the potential dispersal of bacteria from ripe, cankered fruit and the risk posed by this souce of inoculum to the spread of the pathogen in new locations. Piles of cankered fruit were placed in a cull pile and subject to wind speeds of 0, 10, and 25 m/sec and rainsplash, simulating storm conditiond typical of Florida. The wind blown splash was collected and canker-susceptible plants were exposed to the splash from the fruit. Only one plant downwind became infected, developing a single lesion. Wind-blown spray collected onto nutrient agar showed up to 40/ml were Xac. Dispersal of Xac from mature fruit that might be discarded appears to be low. Leaf infections rarely occur, even at high wind speeds.

Technical Abstract: Citrus canker (Xanthomonas axonopodis pv. citri , Xac) is a bacterial disease that severely damages citrus crops. Its recent introduction to Florida has created difficulties with international and domestic trade and movement of citrus material. This study examined the potential dispersal of bacteria from ripe, cankered fruit. Cankered, field collected fruit were placed in a cull pile or suspended in front of a wind/rain source. Wind speeds of 0, 10, and 25 m/sec were generated by an air boat fan which blew simulated rain from spray nozzles across the cankered fruit. The wind blown splash was collected on plexiglass panels and on young grapefruit plants in flush, positioned at 0, 2, 5, and 10m from the fruit. The plants were incubated in a greenhouse and assessed for infection after 3 weeks. Only one plant downwind became infected, and developed a single lesion. Wind-blown spray collected on panels plated onto nutrient agar collected up to 470 total bacteria/ml. Typical xanthomonad-like yellow colonies accounted for up to 300/ml, and ELISA dot blot indicated up to 40/ml were possibly Xac. Dispersal of Xac from cull piles and suspended fruit appears to be low. Leaf infections rarely occur, even at high wind speeds.

Last Modified: 11/1/2014
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