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POSTERS: Population biology and genetics

Assessing the occurrence of bacterial spot of tomatoes in Illinois and identifying species causing the disease
Sabin Khanal - University of Illinois at Urbana Champaign. Sarah R. Hind- 259 E R Madigan Laboratory, Mohammad Babadoost- University of Illinois - Crop Sciences Dept

Bacterial spot, caused by Xanthomonas spp., is one of the most important diseases of tomato in Illinois. Field surveys were conducted in 2017 and 2018 to assess occurrence of bacterial spot in commercial tomato fields in Illinois. Diseased samples were collected from three to five cultivars of tomatoes and from two to four different fields in each of southern, central, and northern regions of Illinois. Tomato cultivars included in this study were Biltmore, Brandywine, Carolina Gold, Chefs Choice, Dixie Red, Heirloom, Phoenix, Primo Red, Pony Express, Red Duce, Red Morning, and Rocky Top. Disease severity on leaves in 2017 ranges from 3% (‘Rocky Top’, central region) to 38% (‘Heirloom’, southern region). In 2018, disease severity on leaves ranged from 9% (‘Red Duce’, central region) to 91% (“Red Duce’, northern region). Overall, severity of bacterial spot in 2018 was higher than that in 2017. During 2017-2018, 159 Xanthomonas isolates from 146 symptomatic leaf and fruit samples were collected and 102, 56, and 1 isolates were identified as X. gardneri, X. perforans, and X. euvesicatoria, respectively. The findings of this study are expected to help to develop effective management of bacterial spot of tomatoes.