Identification and characterization of Didymella bryoniae causing gummy stem blight disease of watermelon (Citrullus lanatus) in Turkey Esin Basım a, * , Hüseyin Basım b , Muntala Abdulai b , Derya Baki b , Nurhan € Oztürk a a Akdeniz University, Korkuteli Vocational School, Horticulture Department, Korkuteli, Antalya, Turkey b Akdeniz University, Faculty of Agriculture, Department of Plant Protection, Antalya, Turkey article info Article history: Received 26 May 2016 Received in revised form 23 August 2016 Accepted 24 August 2016 Keywords: Didymella bryoniae Gummy stem blight Cucurbits PCR abstract Watermelon (Citrullus lanatus (Thunb.) Matsum. & Nakai) is an important plant in the family Cucurbi- taceae. Didymella bryoniae (Auersw.) Rehm [anamorph Phoma cucurbitacearum (Fr.) Sacc.] is the causative agent of gummy stem blight (GSB), a disease affecting members of the family Cucurbitaceae. Watermelon seedlings showing varied degree (20e90%) of suspected GSBs were collected from seedling companies in Antalya province, Turkey. The symptoms included angular water-soaked lesions, which turned tan over time; defoliation; dry, pale green stem; stem necrosis; gummy exudates; wilt; and the eventual death of the upper parts of the seedling plants. The growth of the fungal isolate in vitro showed white aerial and olivaceous mycelium, and olive to dark green or black substrate mycelium at the latter period of fungal growth. The colony surface was rough and undulated. The conidia were round-ended, cylindrical, monoseptate, and hyaline. The conidia ranged from 6.4 to 13.6 mm in length and 3.69e4.68 mm in diameter. The isolates were subjected to PCR using three primers, namely, DB-F3/DB-R3, GSBF1/GSBR1, and ITS1/ITS4, which produced fragment sizes of approximately 120, 780, and 560 bp, respectively. The real-time PCR using DB-F3/DB-R3 primer and SYBR Green fluorescence dye produced positive result for the samples tested. The D. bryoniae isolate was pathogenic to all the four different cucurbits tested and were consistently re-isolated from the diseased seedlings confirming their pathogenic status and thereby satisfying Koch's postulates. This is the second report confirming the presence of D. bryoniae in Turkey after its first detection in cucumber in 2015. © 2016 Elsevier Ltd. All rights reserved. 1. Introduction Watermelon (Citrullus lanatus (Thunb) Matsum. & Nakai) be- longs to the family Cucurbitaceae (gourds and melon family). This is a genetically diverse family (wild edible and non-edible wild) that includes frost-sensitive vine crops, which consists of various economically significant crop species such as watermelon C. lanatus (Thunb.), melon (Cucumis melo L.), pumpkin/squash (Cucurbita spp.), and cucumber (Cucumis sativus L.) (Robinson and Decker, 1997). Turkey is the second largest producer of melon in the world, producing 1,708,415 tons of melon from 102,000 ha (FAOSTAT, 2012). Watermelon is one of the economically important vegetable plants in the family Cucurbitaceae and is produced mainly for its edible flesh (Robinson and Decker, 1997). Approxi- mately 70% of the nearly 100 vegetable-seedling companies in Turkey are located in Antalya province in the western Mediterra- nean region. Watermelon is an extremely important vine plant with respect to its production value. Watermelon seeds are an important source of nutrient and play an important role in com- plementing the nutritional requirement of the poor, who cannot afford animal-based protein foods (Achu et al., 2005). Cultivation of watermelon and other species of the family Cucurbitaceae is severely affected by several pests and pathogens, including Didymella bryoniae which is causative agent of the gummy stem blight (GSB) disease in watermelon plants. This pathogen is assumed to be distributed worldwide, and can be found in high concentrations in Central and South America, Caribbean, Asia, Africa, Europe, and Oceania (CABI, 2015). In Turkey, D. bryoniae pathogen was first reported in cucumber (C. sativus) plants in the greenhouses across various districts in the Elazı g province by Mutlu et al. (2015) with a prevalence rate and disease severity (DS) of 10.79% and 20.02%, respectively. On the basis of the result of molecular analysis of the genomic DNA and the division of the species of Phoma into various clades in * Corresponding author. E-mail addresses: ebasim@yahoo.com, esinbasim@akdeniz.edu.tr (E. Basım). Contents lists available at ScienceDirect Crop Protection journal homepage: www.elsevier.com/locate/cropro http://dx.doi.org/10.1016/j.cropro.2016.08.026 0261-2194/© 2016 Elsevier Ltd. All rights reserved. Crop Protection 90 (2016) 150e156