A Potential Threat for Blackberry, Raspberry and Rosehip Growing in Konya Province: Fire Blight Disease

Abstract

In the present study, totally 49 samples, which showed the symptoms of leaf and shoot blight and cankers with brown discoloration of necrotic tissues on mature branches, were collected from 22 districts and areas of Konya Province between 2017 and 2019. Presence rate of E. amylovora in collected samples, showing symptoms of the disease, from the province was determined to be 40% for blackberry and raspberry and 33% rosehip for rosehip in three years. Bacteria consistently isolated from the diseased tissues were identified on the basis of biochemical, physiological, and molecular tests, comparing with a reference strain of E. amylovora, isolated from blackberry (Kbb 371). Twenty seven representative bacterial strains were gram-negative, rod-shaped, mucoid, fermentative, positive for levan formation and acetoin production, no growth at 36°C, positive for gelatin hydrolysis, and negative for esculin hydrolysis, indole, urease, catalase, oxidase, arginine dehydrolase, reduction of nitrate, acid production from lactose, and inositol. All strains induced a hypersensitive response in tobacco (Nicotiana tobacum cv. White Burley) 24 h after inoculation with a 108 CFU ml-1 bacterial suspension in sterile distilled water. The strains were identified as E. amylovora using the species-specific primers set A/B (1), which amplified a 1-kb DNA fragment in PCR, and the matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) method. In order to fulfill the Koch postulates, pathogenicity test was confirmed by injecting bacterial suspensions of 108 CFU ml-1 in sterile distilled water into the shoot tips of 3-year-old blackberry R. fruticosus cv. Chester, raspberry R. idaeus cv. Heritage and rosehip R. canina. All tests were repeated three times. The bacterium was re-isolated from inoculated plants and identified as E. amylovora. Phytosanitary measures are needed to prevent any further spread of the bacterium as potential inoculum sources to new blackberry, raspberry and rosehip growing areas.