The Aegean region (western Turkey) is the center of table, raisin, and wine grape cultivation. During the 2012 growing season, wood canker symptoms were observed in vineyards in Manisa city. Symptoms adjacent to pruning wounds, including shoot dieback and wedge-shaped wood discolorations observed in cross section, were among the most prevalent symptoms of the vines. To identify the causal agents, symptomatic woody tissues were surface disinfested with 95% ethanol and flame-sterilized and the discolored outer bark was cut away. The internal tissues (0.5 cm2) were excised from cankers of vines and plated onto potato dextrose agar amended with tetracycline (0.01%) (PDA-tet). The most frequently isolated fungi, based on general growth pattern, speed of growth, and colony color, resembled species in the Botryosphaeriaceae family. According to morphological characteristics, four different groups have been identified based on visual discrimination. After DNA extraction, ribosomal DNA fragments (ITS1-5.8S-ITS2) (2) amplified with ITS4 and ITS5 primers were sequenced and sequences were compared with those deposited in NCBI GenBank database. Four different Botryosphaeriaceae isolates were identified, including Botryosphaeria dothidea (MBAi25AG), Diplodia seriata (MBAi23AG), Lasiodiplodia theobromae (MBAi28AG), and Neofusicoccum parvum (MBAi27AG) (Accession Nos. KF182329, KF182328, KF182331, and KF182330, respectively) with species nomenclature based on Crous et al. (1). Pathogenicity tests were conducted under greenhouse conditions (24°C, 16/8-h day/night, 70% RH) on 1-year-old own rooted grapevine (Vitis vinifera) cv. Sultana Seedless seedlings using one isolate from each of the Botryosphaeriaceae species specified above. Stems of grapevine seedlings were wounded by removing bark with 4-mm cork borer and fresh mycelial plugs were inoculated into the holes and covered with Parafilm. Sterile PDA plugs were placed into the wounds of control seedlings. Five vines were inoculated per isolate. The experiment was repeated twice. After 4 months of incubation, grapevine seedlings were examined for the extent of vascular discoloration and recovery of fungal isolates. Mean lesion lengths on wood tissues were 85.3, 17.2, 13.9, and 13.1 mm for N. parvum, B. dothidea, L. theobromae, and D. seriata, and 6.3 mm for control. Each fungal isolate was successfully re-isolated from inoculated seedlings to fulfill Koch's postulates. To our knowledge, this is the first report of multiple species in the Botryosphaeriaceae causing wood canker and dieback on grapevine in Turkey. These results are significant because Botryosphaeriaceae species are known causal agents of grapevine trunk disease worldwide (3).
References: (1) P. W. Crous et al. Stud. Mycol. 55:235, 2006. (2) B. Slippers et al. Mycologia 96:83, 2004. (3) J. R. Urbez-Torres. Phytopathol. Mediterr. 50:S5, 2011.
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