First report of Phytopythium litorale causing root rot of apple in Turkey
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First report of Phytopythium litorale causing root rot of apple in Turkey Figen Mert 1
&
Şahimerdan Türkölmez 2 & Göksel Özer 3 & Sibel Derviş 4 & Osman Çiftçi 5
Received: 13 February 2020 / Accepted: 21 August 2020 # Società Italiana di Patologia Vegetale (S.I.Pa.V.) 2020
Keywords Apple . Phytopythium litorale . Oomycetes
Turkey is the third-biggest producer of apple (Malus domestica Borkh.) in the world with an annual production of about 3 million tons (FAOSTAT 2020). In July 2018, wilting, yellowing, and subsequent death symptoms were observed on about 10% of three-year-old apple trees cultivars grafted to clonal apple rootstock M9 in Çanakkale, Turkey. Larger roots of diseased trees showed a reddishbrown discoloration in the inner bark and most of fine roots completely rotted. To isolate the pathogen, sections (5– 10 mm 2 ) were excised from necrotic tissues, surface disinfected using 2% NaOCl for 1 min, followed by three rinses with sterile water, and plated onto grated apple cornmeal agar (GACMA) amended with 5 mg of pimaricin, 250 mg of ampicillin, 10 mg of rifampicin, 100 mg of pentachloronitrobenzene, and 50 mg of hymexazol per liter (P5ARPH). Oomycete-like isolates were obtained, purified by single-hypha to new plates and, incubated at 20 °C for a week in the dark. Sporangia were nearly globose, 22.7 to 31.1 × 21.2 to 26.9 μm in diameter with a length/width ratio of 1.03 to 1.11 and had mostly apical papillae. Zoospores were released on GACMA under splashing water during the overnight incubation and were 7.9–9.8 μm in diameter.
* Figen Mert [email protected] 1
Department of Plant Protection, Faculty of Agriculture, Çanakkale Onsekiz Mart University, 17100 Çanakkale, Turkey
2
GAP Agricultural Research Institute, 63040 Şanlıurfa, Turkey
3
Department of Plant Protection, Faculty of Agriculture and Natural Sciences, Bolu Abant Izzet Baysal University, 14020 Bolu, Turkey
4
Department of Plant and Animal Production, Vocational School of Kızıltepe Mardin Artuklu University, 47000 Mardin, Turkey
5
Diyarbakır Plant Protection Research Station, 21110 Diyarbakır, Yenişehir, Turkey
Spherical hyphal swellings were plentiful in GACMA, 19.5 to 32.8 μm in diameter, and formed terminally or intercalary. No oospores were observed on cultures after several weeks of incubation in the dark. The pathogen was identified as Phytopythium litorale (Nechw.) Abad, De Cock, Bala, Robideau, Lodhi & Lévesque based on these morphological features (Nechwatal and Mendgen 2006). The internal transcribed spacer (ITS) and the large subunit (LSU) of rDNA and mitochondrial cytochrome oxidase II gene (cox II) of two representative isolates were sequenced, deposited in the GenBank database (accession Nos. MT041698–99, MT042002–03, and MT050457–58) and comparisons with those of P. litorale (AB920537, HQ643386, and AB690664) showed 100% nucleotide identities, respectively. To confirm pathogenicity, primary roots of two-year-old M9 rootstocks were wounded by removal of a plug of tissue with a 7-mm diameter cork borer a
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