First report of Neoscytalidium dimidiatum causing tuber rot of potato in Turkey
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First report of Neoscytalidium dimidiatum causing tuber rot of potato in Turkey Sibel Derviş 1
&
Göksel Özer 2 & Şahimerdan Türkölmez 3
Received: 3 February 2020 / Accepted: 12 May 2020 # Società Italiana di Patologia Vegetale (S.I.Pa.V.) 2020
Keywords Potato . Neoscytalidium dimidiatum . Tuber rot
In July 2019, during and just after harvest, potato (Solanum tuberosum L.) tubers exhibited wrinkled and dark depressions on the surface with an incidence of 5% in two production fields examined in Şanlıurfa, Turkey. Black necrotic symptoms on the surface expanded to the center of tubers. The infected tuber tissues were subjected to pathogen isolation by excising pieces of necrotic tissue to place onto potato dextrose agar (PDA) followed by superficial disinfestation. After incubation at room temperature for five days in the dark, dark-green to black with abundant arthroconidia in aerial mycelia was formed on PDA, and hyphal tips were transferred on new PDA plates to purify the pathogen. Conidia (n = 50) were thick-walled, rod-shaped, 5.9 to 11.4 × 2.6 to 4.5 μm, formed singly or in arthric chains by hyphal fragmentation, and observed to have 1 or 2 cells. Pycnidia (n = 30) were formed on pine needles in culture as semi-immersed or superficial with a mean diameter of 280 μm. Pycniospores (n = 50) were hyaline, ellipsoidal, becoming sepia 0–1-septate, 3.4 to 4.5 × 11.4 to 13.8 μm These morphological characteristics were consistent with the description of Neoscytalidium spp. by Phillips et al. (2013). The internal transcribed spacer (ITS) and the large subunit (LSU) of rDNA and the translation elongation factor 1-α gene (EF1-α) for two isolates of Neoscytalidium sp. were sequenced and
deposited in the GenBank with the accession Nos. MT010216-MT010217, MT010293-MT010294, and MT362600-MT362601, respectively. A BLASTn search of the sequences in GenBank revealed 99.64, 99.77, and 99.66% sequence identity with those of the type specimen of Neoscytalidium dimidiatum (Penz.) Crous & Slippers strain CBS 145.78 (ITS MH861121; LSU DQ377922; EF1-α KF531795). The phylogenetic analysis based on sequences of isolates in this study and those of Neoscytalidium spp. isolates available in GenBank verified the identification. To confirm the pathogenicity of two isolates, five tubers of potato cv. Agria for each isolate were wounded by removal of a plug of tissue with a depth of 5-mm and a 5-mm diameter cork borer and inoculated by 5-mm mycelial plugs from a seven-day-old culture. Noncolonized mycelial plugs served as controls. Inoculated tubers were transferred to a growth chamber at 24 °C with a 12-h photoperiod. After three weeks, black necrotic lesions occurred into the center of tubers inoculated with N. dimidiatum but no symptoms were observed on control tubers. Neoscytalidium dimidiatum was re-isolated from symptomatic tubers, confirming Koch’s postulates. To our knowledge, this is the first report of Neoscytalidium dimidiatum causing tuber rot of potato in Turkey and worldwide (Farr and Rossman 2020).
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