Grapevine (Vitis vinifera L.) is a widely planted and economically important crop for production of raisin grapes, table grapes, and wine grapes in Turkey. Esca and petri diseases are two of the most important and destructive diseases of young and old vines worldwide (1). During the summers of 2009 and 2010, a survey was carried out in 63 vineyards in six locations of Ankara Province. Root and trunk samples were collected from 4- to 15-year-old grapevines showing esca and petri disease symptoms, including reduced trunk diameters, shortened internodes, stunted growth, chlorotic or necrotic leaves, and brown-to-black spots or streaks in the xylem vessels in cross or longitudinal sections of the rootstock trunk (1,3). Small pieces of internal tissues were surface disinfested in 1% sodium hypochlorite for 2 min, washed twice with sterile distilled water, and plated onto potato dextrose agar (PDA) amended with tetracycline hydrochloride (0.1 g liter–1). Plates were incubated at 25°C in the dark for 14 to 21 days. Phaeoacremonium spp. were consistently isolated from necrotic tissues. Single-conidial isolates of these Phaeoacremonium spp. were grown on PDA, malt extract agar (MEA), and oatmeal agar (OA) in the dark at 25°C for 2 to 3 weeks until colonies produced spores (3). Of these, Phaeoacremonium aleophilum was the most prevalent species, however, one isolate identified as P. scolyti was described by L. Mostert et al. (3). Conidiophores were mostly short and usually unbranched, subcylindrical to navicular, and often consisting of an elongate-ampuliform phialide. Phialides were terminal or lateral and pale brown to hyaline. Type II phialide were predominant. Type I phialide were 4 to 6 μm (average), type II phialide were 7 to 14 μm (average), and type III phialide were 14 to 20 μm (average). Conidia were hyaline, oblong-ellipsoidal, occasionally reniform or allantoid, 2.5 to 5 μm long (average), and 1 to 1.5 μm wide (average). Colony colors were reddish gray on PDA, pinkish white on MEA, and grayish pink on OA. Identity was confirmed by β-tubulin sequence analysis using primers T1 and Bt2b (2). Additionally, the β-tubulin gene fragment (primers T1 and Bt2b) of this isolate was sequenced (GenBank Accession No. JF909894). The sequence showed high similarity (99%) with the sequence of P. scolyti (GenBank Accession No. EU260415). Pathogenicity tests were completed using five, 3-month-old rooted cuttings of cv. Sultana. A hole approximately 3 mm in diameter was drilled on the crown 2 cm aboveground level from the bark to the pith and filled with a 30-μl spore suspension (106 spores/ml) harvested from 21-day-old cultures grown on PDA at 25°C in the dark. Five control plants were used. Controls were inoculated with sterile distilled water. Filled holes were sealed with a sheet of Parafilm. The plants were incubated for 3 months in a controlled environment facility at 25°C. After 3 months, the fungus was reisolated from black discoloration of vascular tissue and pith tissue of the crown area of all inoculated cuttings, completing Koch's postulates. The black discoloration was more compact near the point of inoculation. Control plants were asymptomatic and P. scolyti was not recovered from control plants. To our knowledge, this is the first report of the presence of P. scolyti causing esca and petri disease of grapevine in Turkey.
References: (1) A. Eskalen et al. Plant Dis. 91:1100, 2007. (2) S. Essakhi et al. Persoonia 21:119, 2008. (3) L. Mostert et al. Stud. Mycol. 54:1, 2006.
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