title: Interactions of seedborne bacterial pathogens with host and non-host plants in relation to seed infestation and seedling transmission.
abstract: The ability of seed-borne bacterial pathogens (Acidovorax citrulli, Clavibacter michiganensis subsp. michiganensis, Pseudomonas syringae pv. tomato, Xanthomonas euvesicatoria, and Pseudomonas syringae pv. glycinea) to infest seeds of host and non-host plants (watermelon, tomato, pepper, and soybean) and subsequent pathogen transmission to seedlings was investigated. A non-pathogenic, pigmented strain of Serratia marcescens was also included to assess a null-interacting situation with the same plant species. Flowers of host and non-host plants were inoculated with 1 × 10(6) colony forming units (CFUs)/flower for each bacterial species and allowed to develop into fruits or umbels (in case of onion). Seeds harvested from each host/non-host bacterial species combination were assayed for respective bacteria by plating on semi-selective media. Additionally, seedlots for each host/non-host bacterial species combination were also assayed for pathogen transmission by seedling grow-out (SGO) assays under greenhouse conditions. The mean percentage of seedlots infested with compatible and incompatible pathogens was 31.7 and 30.9% (by plating), respectively and they were not significantly different (P = 0.67). The percentage of seedlots infested with null-interacting bacterial species was 16.8% (by plating) and it was significantly lower than the infested lots generated with compatible and incompatible bacterial pathogens (P = 0.03). None of the seedlots with incompatible/null-interacting bacteria developed symptoms on seedlings; however, when seedlings were assayed for epiphytic bacterial presence, 19.5 and 9.4% of the lots were positive, respectively. These results indicate that the seeds of non-host plants can become infested with incompatible and null-interacting bacterial species through flower colonization and they can be transmitted via epiphytic colonization of seedlings. In addition, it was also observed that flowers and seeds of non-host plants can be colonized by compatible/incompatible/null-interacting bacteria to higher populations; however, the level of colonization differed significantly depending on the type of bacterial species used.
authors.affiliation: Department of Plant Pathology, University of Georgia, Coastal Plain Experiment Station, Tifton, Georgia, United States of America.
authors.forename: Bhabesh
authors.initials: B
authors.lastname: Dutta
authors.affiliation: Department of Plant Pathology, University of Georgia, Coastal Plain Experiment Station, Tifton, Georgia, United States of America.
authors.forename: Ronald
authors.initials: R
authors.lastname: Gitaitis
authors.affiliation: Department of Plant Pathology, University of Georgia, Coastal Plain Experiment Station, Tifton, Georgia, United States of America.
authors.forename: Samuel
authors.initials: S
authors.lastname: Smith
authors.affiliation: Department of Plant Pathology, University of Georgia, Coastal Plain Experiment Station, Tifton, Georgia, United States of America.
authors.forename: David
authors.initials: D
authors.lastname: Langston
mesh_terms: D002212:Capsicum / Q000382:microbiology; D029773:Citrullus / Q000382:microbiology; D042621:Comamonadaceae / Q000502:physiology; D035264:Flowers / Q000382:microbiology*; D058507:Host Specificity; D018551:Solanum lycopersicum / Q000382:microbiology; D010935:Plant Diseases / Q000382:microbiology*; D044224:Pseudomonas syringae / Q000502:physiology; D036226:Seedlings / Q000382:microbiology*; D012639:Seeds / Q000382:microbiology*; D013025:Glycine max / Q000382:microbiology; D014974:Xanthomonas / Q000502:physiology