First report of fire blight disease caused by Erwinia amylovora on Rockspray (Cotoneaster horizontalis) in Turkey

In the late summer and early winter of 2008 and 2009, leaf and shoot blight and cankers with reddish and brownish necrotic tissue on mature branches of Cotoneaster horizontalis were investigated in landscape areas of Konya province in Turkey. Disease incidence was estimated at 2%. Bacteria were consistently isolated from the lesions on leaves and shoots on nutrient sucrose agar medium. Twelve representative bacterial strains were isolated and characterized as gram-negative, rod-shaped, mucoid, fermentative, yellow-orange on MS medium, positive for levan formation and acetoin production, no growth at 36°C, positive for gelatin hydrolysis, and negative for indole, urease, oxidase, arginine dehydrolase, reduction of nitrate, and acid production from lactose and inositol (2). Two reference strains of Erwinia amylovora (EaP28 and NCPPB 2791) obtained from the culture collection unit of Selcuk University were used as positive controls. All strains induced a hypersensitive response in tobacco (Nicotiana tobaccum cv. White Burley). All strains were identified as E. amylovora on the basis of amplification of a 1 kb DNA fragment with a species-specific primer set, A/B (1) by PCR, and fatty acid methyl ester profiles determined by Sherlock Microbial Identification System software (TSBA 6 v. 6.00; Microbial ID, Newark, DE) with similarity indices ranging from of 83 to 96%. Pathogenicity tests were performed by injecting 20 µl of a bacterial suspension (108 CFU ml-1) into the shoot tips of 3-year-old C. horizontalis seedlings. Leaf and shoot blighting symptoms were observed within 10 to 15 days, but no symptoms were observed on control plants treated with sterile water. The bacterium was reisolated from the lesions on leaves and shoots and identified as described above. To our knowledge, this is the first report of E. amylovora on cotoneaster in Turkey. Control measures are needed to prevent any further spread of the bacterium to new landscape areas. © 2012 The American Phytopathological Society.