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Ecology and Epidemiology

Survival of Pseudomonas syringae pv. tomato in Association with Tomato Seed, Soil, Host Tissue, and Epiphytic Weed Hosts in Georgia. S. M. McCarter, Professor, Department of Plant Pathology, University of Georgia, Athens 30602; J. B. Jones(2), R. D. Gitaitis(3), and D. R. Smitley(4). (2)(4)Former postdoctoral associate, and former graduate assistant, respectively, Department of Plant Pathology, University of Georgia, Athens 30602; (3)Assistant professor, Georgia Coastal Plain Experiment Station, Tifton 31793. Phytopathology 73:1393-1398. Accepted for publication 20 April 1983. Copyright 1983 The American Phytopathological Society. DOI: 10.1094/Phyto-73-1393.

Pseudomonas syringae pv. tomato (PST) was recovered from 19 of 1,566 samples of commercial tomato seed lots used for transplant production in southern Georgia in 1979- 1982. The bacterium was also recovered from a diverse group of symptomless weed species growing in tomato fields near Athens, GA, during 1980- 1981, but not from 48 weed or volunteer crop plant species collected from tomato transplant fields near Tifton in 1979- 1981. Results of an Athens test indicated that PST is disseminated to spring-seeded tomatoes after overwintering on native weeds. PST declined rapidly in both natural soil and buried host debris. In one test, it was not detected in artificially-infested (10⁹ cfu/g) soil or buried host tissue when assayed 15 and 24 days after being placed in buried pots in fields at Tifton and Athens, respectively. Low populations were detected in tissue left on the soil surface for 15 and 24 days, but not when second assays were run after 45 days at Tifton and 60 days at Athens. In another test at Tifton. PST did not survive from June until the following March in diseased host tissue left on the surface or incorporated 15- 20 cm deep. In temperature tanks, PST was recovered for <1 mo at 33- 38 C whether free in the soil or in host tissue, but survived at least 81 days in host tissue buried in natural soil at 18 C. Our results suggest that seed and weed hosts are likely sources of primary inoculum in tomato fields. Survival of PST in either soil or host debris is highly unlikely under high soil temperature conditions in southern Georgia but is possible where temperatures are lower.