First report of shoot blight and branch canker of Pyrus communis by Neoscytalidium novaehollandiae in Turkey

Abstract

Turkey is the world’s fifth-largest pear (Pyrus communis L.) producer with a production of 503.000 tons and a cultivated area of 26.000 ha (FAOSTAT 2020). In June 2019, symptoms of shoot blight and branch canker showing intensely dark wood discoloration, and dieback were observed on about 10% of pear trees (cv. Deveci) in two commercial orchards, 70 km away from each other in Battalgazi (38.466659 N 38.343073E) and Doğanşehir (38.085506 N 37.896307E) districts in Malatya province, Turkey. Small pieces of symptomatic tissues (5–10 mm2) were excised from symptomatic tissues of stems/branches and subjected to surface disinfection by immersing them in 1% NaOCl for 1 min and in sterile water twice. Pieces of tissues were then plated onto potato dextrose agar (PDA). Finally, four isolates were obtained after an incubation period at room temperature for five days and purified on PDA. The isolates were developed as dark gray to black with abundant arthroconidia in aerial mycelia. Arthroconidia (n = 50) were thick-walled, 0 to 1 septate, rod-shaped, 5.1 to 9.7 × 3.1 to 4.6 μm, and formed singly or in arthric chains. Pycniospores (n = 50) produced on pine needles on 1.5% water agar were hyaline, ellipsoidal, 0–1-septate, 2.9 to 4.2 × 11.9 to 14.3 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 (EF1a) gene for a representative isolate (Mlty_01) were sequenced (GenBank accession Nos. MT041243, MT038898, and MT710710), and comparisons with those of Neoscytalidium novaehollandiae Pavlic, T.I. Burgess & M.J. Wingf. strain WAC12693 (EF585538, EF585551, and EF585576) showed 99–100% nucleotide identity for ITS, LSU, and EF1α, respectively. To confirm the pathogenicity of the isolate, five 2-year-old branches of pear cv. Deveci were wounded by removal of a plug of tissue with a depth of 2-mm and a 5-mm diameter cork borer and inoculated by 5-mm mycelial plugs from one-week-old culture. Sterile mycelial plugs were used as controls. Inoculated branches were immediately transferred to a growth chamber at 24 °C in a 12-h photoperiod. After one-month, necrotic lesions were observed on all inoculated branches, while all controls remained healthy. The fungus was re-isolated from lesions successfully. To our knowledge, this is the first report of shoot blight and canker on pear trees by N. novaehollandiae in Turkey and worldwide (Farr and Rossman 2020).