title: Occurrence of copper-resistant strains and a shift in Xanthomonas spp. causing tomato bacterial spot in Ontario.
abstract: Field strains of tomato bacterial spot pathogen (Xanthomonas euvesicatoria, X. vesicatoria, X. perforans, and X. gardneri) were characterized for sensitivity to copper and species composition. A total of 98 strains were isolated from symptomatic leaf and fruit samples collected from 18 tomato fields in Ontario. In greenhouse pathogenicity tests, most of the field strains caused severe (37 strains) to highly severe (23 strains) symptoms on 'Bonny Best' tomato plants, whereas 38 strains caused moderate symptoms. In MGY agar plates amended with various concentrations of copper sulfate, 11 strains were completely sensitive (no growth) and 87 strains were resistant (grew on 1.0 mmol/L or higher copper concentration). PCR analysis of the hrp gene cluster followed by restriction digestion with HaeIII and sequencing identified X. gardneri (35 strains) and X. perforans (26 strains) as predominant species and X. euvesicatoria and X. vesicatoria as less common species in Ontario tomato fields. Separation of field strains into various species was also confirmed with starch hydrolysis activity on agar medium. Moreover, 72 field strains produced shiny greenish-yellow colonies surrounded by a milky zone on xanthomonad differential (Xan-D) medium, and the colonies of 26 strains did not produce a milky zone. Thirty-four strains could not be clustered into any species and 25 of those strains were negative for the hrp gene PCR and also did not produce a milky zone around colonies on Xan-D medium. Our results suggest a widespread existence of copper-resistant strains and an increase in X. perforans strains of bacterial spot pathogen in Ontario. This information on copper resistance and species composition within bacterial spot pathogens in Ontario will be helpful for developing effective disease management strategies, making cultivar selection, and breeding new tomato cultivars.
authors: Southern Crop Protection and Food Research Centre, Agriculture and Agri-Food Canada, 1391 Sandford Street, London, ON N5V 4T3, Canada.|Southern Crop Protection and Food Research Centre, Agriculture and Agri-Food Canada, 1391 Sandford Street, London, ON N5V 4T3, Canada.
authors: Pervaiz A
authors: PA
authors: Abbasi
authors: Southern Crop Protection and Food Research Centre, Agriculture and Agri-Food Canada, 1391 Sandford Street, London, ON N5V 4T3, Canada.|Southern Crop Protection and Food Research Centre, Agriculture and Agri-Food Canada, 1391 Sandford Street, London, ON N5V 4T3, Canada.
authors: Salah Eddin
authors: SE
authors: Khabbaz
authors: Southern Crop Protection and Food Research Centre, Agriculture and Agri-Food Canada, 1391 Sandford Street, London, ON N5V 4T3, Canada.|Southern Crop Protection and Food Research Centre, Agriculture and Agri-Food Canada, 1391 Sandford Street, London, ON N5V 4T3, Canada.
authors: Brian
authors: B
authors: Weselowski
authors: Southern Crop Protection and Food Research Centre, Agriculture and Agri-Food Canada, 1391 Sandford Street, London, ON N5V 4T3, Canada.|Southern Crop Protection and Food Research Centre, Agriculture and Agri-Food Canada, 1391 Sandford Street, London, ON N5V 4T3, Canada.
authors: Liang
authors: L
authors: Zhang
mesh_terms: D003300:Copper / Q000494:pharmacology*; D018551:Solanum lycopersicum / Q000382:microbiology*; D008826:Microbial Sensitivity Tests; D005810:Multigene Family; D009864:Ontario; D010935:Plant Diseases / Q000382:microbiology*; D018515:Plant Leaves / Q000382:microbiology; D014974:Xanthomonas / Q000187:drug effects / Q000235:genetics / Q000472:pathogenicity / Q000502:physiology*
chemical_list: D003300:Copper
keywords: Solanum lycopersicum; Xanthomonas gardneri; Xanthomonas perforans; copper sensitivity; sensibilité au cuivre