Cytospora schulzeri Sacc. & P. Syd., Syll. Fung. (Abellini) 14(2): 918 (1899)

Index Fungorum number: IF 140461; MycoBank number: MB 140461; Facesoffungi number: FoF 01022; Figs. 1, 2

Associated with branch canker and dieback of Malus species. Sexual morph: not observed. Asexual morph: Conidiomata pycnidial, forming within 10 days, irregularly scattered on the surface of the colonies in culture. Conidiophores hyaline, reduced to conidiogenous cells. Conidiogenous cells hyaline, phialidic, 9.8 11.5–12.8 × 1.0–1.4–2.0 µm (n = 20). Conidia hyaline, aseptate, allantoid to slightly curved, eguttulate, 3.0–5.2–6.9 × 1.0–1.5–2.0 µm (n = 20).

Culture characteristics – Colonies on PDA at 21 °C and incubated under black light reached 14–19 mm in diameter after three days, covering the 9 cm Petri dish in seven days with even margin expansion, flat, without aerial mycelium, white to buff on the surface, white to light brown on reverse.

Material examined – NEW ZEALAND, Ettrick, Roxburgh, from branch canker of Malus domestica, August 2020, M. Braithwaite, PDL3791, PHEL T20_01779. Culture stored at the International Collection of Microorganisms from Plants (ICMP23778).

Known hosts and distribution – RUSSIA, on Malus domestica (Ariyawansa et al. 2015a); CHINA, on Malus sieversii (Ma et al. 2018); IRAN, on Malus domestica (Hanifeh et al. 2022); NEW ZEALAND, on Malus domestica (this study).

GenBank – ICMP23778: OR807323 (ITS), OR808085 (LSU), OR814106 (act), OR814110 (rpb2), OR814114 (tef1), OR814118 (tub2).

Notes – In phylogenetic analysis, ICMP23778 grouped in a strongly supported monophyletic clade with other C. schulzeri sequences. Pathogenicity testing with isolate ICMP23778 showed some pathogenicity towards Malus domestica. Approximately a third of infected detached apple shoots developed internal necrosis after inoculation with C. schulzeri, confirming earlier reports of this species being an opportunistic plant pathogen. Previously, C. leucostoma of Cytospora sp. have been reported from Malus sp. in New Zealand, dating back to as early as 1926 (Landcare Research 2023). No cultures have been stored for these find and therefore their identity cannot be verified. This is the first record of C. schulzeri from New Zealand. Note that this organism was first identified as Cytospora parasitica but has been amended to Cytospora schulzeri given the taxonomic revisions of Lin et al. (2024).

Figure 1 – Maximum likelihood (GTR + G + I) tree illustrating the phylogenetic placement of the Cytospora species discussed in-text (in bold) within the genus. This phylogenetic tree is based on the alignment of concatenated ITS, act and rpb2 sequences. Branches are labelled with bootstrap prob abilities = 70% across 1,000 bootstrapping replicates, and type specimens are denoted by a superscript “T”. Diaporthe vaccinii CBS 160.32 was used as an outgroup.

Figure 2 – Cytospora schulzeri (ICMP23778). a Symptoms found on host. b across section of a conidiomata. c Colony on PDA media after 7 days. d Conidiomata on a colony in pure culture. e, f Conidiogenous cells. g Conidia. Scale bars = 10 µm