First report ofNeoscytalidium dimidiatumcausing shoot blight, dieback and canker of apricot in Turkey

Abstract

Turkey is the largest apricot (Prunus armeniaca L.) producing country worldwide with almost 17 million trees producing fruits (TUIK 2019). In June 2018, shoot blight, branch dieback and canker symptoms were observed on about 9% apricot trees in the orchards examined in Malatya province (Turkey), which is alone responsible for 15.8% of world production of apricots. Symptomatic tissues were excised from stems and branches of diseased trees and superficially disinfected with 2% sodium hypochlorite for 2 min, twice rinsed, and air dried. The pieces were placed into Petri dishes containing potato dextrose agar (PDA) and incubated at 25 °C in the dark for 7 days. A total of 17 isolates were identified as Neoscytalidium-like based on macro- and micro-morphological characteristics of colonies. The colonies developed a dark green color. Conidia formed as arthric chains from mycelia were dark brown, thick-walled, 6.7 to 11.7 × 2.4 to 4.6 μm (n = 50), ovate to rectangular and observed to have 0- to 1-septa (Phillips et al. 2013). Pycnidia emerged on pine needles in the culture were stromatic, immersed, and dark brown to black. The internal transcribed spacer (ITS), the translation elongation factor 1-α gene (EF1-α), the β-tubulin gene (BT2), and the large subunit of rRNA (LSU) gene sequences from a reference apricot isolate of Neoscytalidium sp. (Kale4-C) were amplified, sequenced, and deposited in the GenBank database (Accession Nos. MK788362, MK803351, MK803352, and MK803393, respectively). A BLASTn search of the resultant sequences showed 99.35–100% sequence homology with those of Neoscytalidium dimidiatum (Penz.) Crous & Slippers strain CBS 145.78 (ITS MH861121, EF1-α KF531795; BT2 KF531796; LSU DQ377922). Pathogenicity tests conducted by inoculating 2-year-old branches with 5-cm mycelial plugs of the reference isolate. Plugs were placed in wounds made with a sterile blade in the inner bark of plant branches. Non-colonized agar plugs were used as control. Inoculated and control branches were maintained in a growth chamber at 25 °C in a 12-h photoperiod. After three weeks, dark-brown discoloration was observed on all inoculated branches, whereas all controls remained symptomless. The fungus was re-isolated from lesions successfully to fulfill Koch’s postulates. To our knowledge, this is the first report of N. dimidiatum causing shoot blight, dieback and canker of apricot in Turkey (Farr and Rossman 2019).