Nectria dematiosa (Schwein.) Berk.

Yang, Qin, Du, Zhuo, Liang, Ying-Mei & Tian, Cheng-Ming, 2018, Molecular phylogeny of Nectria species associated with dieback and canker diseases in China, with a new species described, Phytotaxa 356 (3), pp. 199-214 : 207-208

Nectria dematiosa (Schwein.) Berk. , Grevillea 4: 16, 1875. FIGURES 4–5 .

Host/distribution:—Pathogen on twigs and branches of Acer sp. , Betula albosinensis , Cerasus japonica , Crataegus pinnatifida , Hippophae rhamnoides , Malus baccata , Malus transitoria , Picea crassifolia , Robinia sp. , Rosa xanthine , Sorbaria sorbifolia , and Spiraea salicifolia . Known from Acer macrophyllum , Acer pseudoplatanus , Ribes sp. , Rosa sp. in Canada; Amygdalus nana , Prunus tenella in Finland; Weigela coraeensis in Japan; Sambucus canadensis subsp. canadensis in Nebraska; Ribes sativum in New Zealand; and Morus sp. in Pennsylvania, USA ( Hirooka et al. 2011, 2012).

Asexual morph:— Tubercularia vulgaris -like.

Sexual morph on natural substrata:— Mycelium not visible around ascomata and on host. Stromata erumpent through epidermis, up to 0.3 mm in height and 1.5 mm in diameter, orange to bay, sometimes darker red, KOH+ dark red, LA+ yellow, pseudoparenchymatous, cells forming textura angularis to t. prismatica, intergrading with basal ascomatal wall. Ascomata superficial on well-developed, erumpent stroma, gregarious, up to 2–20 on a stroma, rarely clustered around sessile sporodochia, subglobose to globose, 265–465 μm in height, 260–400 μm in diameter (n = 50), red to reddish brown, sometimes cupulate upon drying, non-papillate, apical region darker, KOH+ dark red, LA+ yellow, surface roughened or with concolourous warts, but sometimes smooth. Ascomatal surface cells forming textura globulosa or t. angularis, with walls pigmented, ca. 1.5 μm thick. Ascomatal wall ca. 35–55 μm thick, consisting of two regions: outer region ca. 25–40 μm thick, intergrading with stroma, cells forming textura globulosa or t. angularis, walls pigmented, ca. 1.5 μm thick; inner region ca. 10–15 μm thick, consisting of elongated, thin-walled, hyaline cells, forming textura prismatica. Asci unitunicate, cylindrical to narrowly clavate, with an inconspicuous ring at apex, 8-spored, ascospores biseriate above, uniseriate below, (60–)65–85(–95) × (7–)7.5–9(–9.5) μm (n = 50). Ascospores ellipsoidal to fusiform, sometimes long fusiform, straight or slightly curved, hyaline, smooth walled, 0–1-septate, Subclade A (12.6–)15.0–18.0(–21.0) × (3.4–)3.6–4.4(–5.1) μm (n = 50), Subclade B and C were not seen.

Asexual morph on natural substrata:— Stromata erumpent through epidermis, orange to red. Sporodochial conidiomata without stipe, superficial on well-developed stromata, smooth, cerebriform or tuberculate, scattered, solitary, rarely caespitose, astipitate, sessile, pustular, discoid or cylindrical-capitate, up to 250–900 μm in height, 350–1000 μm in width, white, whitish yellow to orange, sometimes brown. Hymenium arising directly from textura prismatica elongating from t. angularis, up to 85 μm in length, consisting of cells 2.0–6.5 μm in width, not curved at the margin. Acropleurogenous conidiophores monoverticillate or sometimes biverticillate, then developing acropleurogenously for 3–6 levels, straight, curved, hyaline. Acropleurogenously developing phialides intercalary occurring below each septate, or rarely terminal; intercalary phialides monophialidic, 12.5–21.0 μm long, 1.4–2.1 μm wide at base; terminal cells monophialidic, sometimes sterile, no collarettes, 23–26 μm in length, 2.5–3.2 μm in width at the base. Conidia hyaline, narrowly long ellipsoidal to cylindrical, straight or slightly curved, non-septate, (4.5–)5.7–7.6(–8.2) × (1.9–)2.1–2.9(–3.1) μm (n = 50). Subclade A (4.5–)5.5–7.1(–8.8) × (2.0–)2.2–2.6(–2.9) μm (n = 50), Subclade C (6.5–)7.0–8.8(–10.0) × (1.9–)2.1–2.9(–3.1) μm (n = 50).

Cultures: —Colony surface on PDA, radial, sometimes wavy, slightly cottony with aerial mycelium, white to whitish saffron; aerial mycelium is white to whitish yellow; reverse white to slightly whitish yellow.

Notes:— Nectria dematiosa is the most commonly occurring Nectria species, with a diverse range of hosts and a wide geographic range in China. This study is the first report N. dematiosa from Betula albosinensis , Cerasus japonica , Crataegus pinnatifida , Hippophae rhamnoides , Malus baccata , Malus transitoria , Picea crassifolia , Robinia sp. , Sorbaria sorbifolia , and Spiraea salicifolia . Also provided by this study are detailed descriptions of both sexual and asexual morphs, as well as the discovery of asexual morphs of Subclade C, CFCC 52128, which differ from those of Subclades A and B by virtue of their greater conidial size, 7.1–8.8 × 2.1–2.9 μm ( Fig. 5 ).

Figures

FIGURE 4. Sexual morph of Nectria dematiosa from Malus baccata (BJFC-S440).A: Host branch. B–D: Perithecia on natural substrata. E–F: Median section of perithecium. G–I:Asci. J–L: Ascospores. Scale bars: B–C = 1 mm; D–E = 500 μm; F–L = 20 μm.

FIGURE 5. Asexual morph of Nectria dematiosa from Rosa xanthina (BJFC-S441). A: Host branch. B–C: Astipitate sporodochium on natural substrata. D–E: Median section of astipitate sporodochium. F–G: Conidia. H–J: Conidiophores and conidia. Scale bars: B–C = 1 mm; D–E = 500 μm; F–J = 20 μm.