Branch canker of hazelnut trees caused by Botryosphaeria dothidea in Iran

Background and Objectives The Botryosphaeriaceae (Botryosphaeriales, Ascomycetes) is a family of fungi that have a cosmopolitan distribution and occur on a wide range of woody plants. A field survey was conducted on trunk diseases of hazelnut (Corylus avellana L.) trees in Babol (Mazandaran province) during spring and summer of 2016. Symptoms typical of infection by the Botryosphaeriaceae species such as canker and wedge-shaped wood necrosis have been recorded in some trees. Therefore, the objectives of this study were to identify and pathogenicity of the Botryosphaeriaceaeisolates associated with wood necrosis of hazelnut trees in this region of Iran. Materials and Methods Wood samples were collected from branches of trees showing canker and wood necrosis symptoms. Fungal isolation was made from the margin between healthy and necrotic wood tissues. Wood pieces were cut from the affected tissues, surface-disinfected for 1 min in a 0.5 % sodium hypochlorite solution, and washed twice with sterile distilled water. Wood segments were plated on potato dextrose agar (PDA), and incubated at 25 °C in the dark. Single spore cultures were derived from all isolate prior to morphological and molecular identification. Fungal isolates were identified based on morphology, culture characteristics and sequence analysis of the translation elongation factor 1-alpha (tef-1α) region. Pathogenicity test was conducted for representative isolates on detached shoots of hazelnut under greenhouse conditions. Results In this study 31 isolates resembling of the Botryosphaeriaceae in colony and culture (fast growing, greyish to dark cultures) were obtained. According to morphological characters, as well as phylogenetic analyses of tef-1α gene, all isolated were identified as Botryosphaeria dothidea. Selected isolates used in pathogenicity test caused wood discoloration on inoculated branches after 45 days. Our results showed a variation in wood lesion lengths and re-isolation frequencies of inoculated isolates. Discussion This study represents the first attempt to identify and test the pathogenicity of Botryosphaeriaceae associated with canker disease of hazelnut trees in Iran. Some species of Botryosphaeriaceae had previously been found in declining hazelnut trees. However, this is the first report of occurrence and pathogenicity of B. dothidea on hazelnut in the world.