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Nectria-related fungi causing dieback and canker diseases in China ... 49
Nectria-related fungi causing dieback
and canker diseases in China,
with Neothyronectria citri sp. nov. described
Qin Yang1, Wen-Yan Chen1, Ning Jiang1, Cheng-Ming Tian1
1 e Key Laboratory for Silviculture and Conservation of the Ministry of Education, Beijing Forestry Univer-
sity, Beijing 100083, China
Corresponding author: Cheng-Ming Tian (chengmt@bjfu.edu.cn)
Academic editor: R. Phookamsak|Received 10 May 2019|Accepted 28 June 2019|Published 10 July2019
Citation: Yang Q, Chen W-Y, Jiang N, Tian C-M (2019) Nectria-related fungi causing dieback and canker diseases in
China, with Neothyronectria citri sp. nov. described. MycoKeys 56: 49–66. https://doi.org/10.3897/mycokeys.56.36079
Abstract
To clarify phylogenetic relationships amongst Nectria, Neothyronectria and yronectria in Nectriaceae, we
examined detailed morphological characters and performed phylogenetic analyses of a concatenated data-
set, based on the ITS, LSU, tef1 and tub2 DNA sequences of fungal specimens in China. Four species of
nectria-related fungi were identied, i.e. Nectria dematiosa, N. pseudotrichia, Neothyronectria citri and y-
ronectria pinicola. e newly described species, Neothyronectria citri, is characterised by its ascomatal wall
with bright yellow scurf, unitunicate asci, each with 4-spored and ascospores allantoid to short-cylindrical,
uniseriate, muriform, hyaline to slightly yellowish-brown. is species has anities with other one known
species of Neothyronectria and can be distinguished by molecular data.
Keywords
DNA phylogeny, Nectriaceae, Systematic, Taxonomy
Introduction
Nectriaceae Tul. & C. Tul., typied by the genus Nectria (Fr.) Fr., was established by
Tulasne and Tulasne (1865) to include nectria-related fungi having brightly pigmented
ascomata with fusiform to allantoid ascospores and globose to fusiform phialidic conidia
(Rossman et al. 1999, 2013, Rossman 2000, Lombard et al. 2015, Maharachchikum-
bura et al. 2015, Huang et al. 2018, Yang et al. 2018). Members of the family are unied
Copyright Qin Yang et al. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0),
which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
MycoKeys 56: 49–66 (2019)
doi: 10.3897/mycokeys.56.36079
http://mycokeys.pensoft.net
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RESEARCH ARTICLE
Qin Yang et al. / MycoKeys 56: 49–66 (2019)
50
by phenotypic characters such as uniloculate ascomata that are yellow, orange-red to
purple and phialidic asexual morphs. Lombard et al. (2015) dened the generic con-
cepts in Nectriaceae, based on a multi-gene phylogenetic analysis and resolved 47 genera
supported by morphological observations. Since then, Neothyronectria was proposed as a
new genus to accommodate the species, Neothyronectria sophorae, which is known only
from the pycnidial asexual morph (Crous et al. 2016) and Cosmosporella was proposed
as a new genus (Huang et al. 2018), thus 49 genera are now accepted in the Nectriaceae.
Nectria, typied by N. cinnabarina (Tode: Fr.) Fr., was initially established by Fries
(1849). Some species of Nectria are weak parasites of woody plants (Samuels et al.
2009, Hirooka et al. 2011). Hirooka et al. (2012) reviewed the genus, based on the
type and additional herbarium specimens, and accepted 29 species. ey also mono-
graphed the genus yronectria as Pleonectria but because yronectria (1875) is older,
it has priority over Pleonectria (1876) as explained by Jaklitsch and Voglmayr (2014).
Many members of Nectria and yronectria occur on dead corticated twigs or branches
of woody plants worldwide mainly in temperate and subtropical regions (Hirooka et
al. 2012, Jaklitsch and Voglmayr 2014, Zeng and Zhuang 2016). To date, 42 species of
yronectria have been accepted (Jaklitsch and Voglmayr 2014, Voglmayr et al. 2016,
Zeng and Zhuang 2016, Lechat et al. 2018).
During trips to collect forest pathogens in China, several nectria-related fungi as-
sociated with canker or dieback diseases were collected. Based on a multi-locus phylog-
eny (ITS, LSU, tef1 and tub2), we identied four nectria-related species in three genera
of Nectriaceae and propose one new species in Neothyronectria.
Materials and methods
Isolates
Fresh specimens were collected from infected branches or twigs of diverse hosts from
Beijing, Heilongjiang, Jiangxi, Shaanxi and Xinjiang provinces, China. Strains were
isolated from fresh diseased branches and grown from ascospores or conidia by spread-
ing the suspension on the surface of 1.8% potato dextrose agar (PDA), incubated at
25 °C for up to 24 h. Single germinating conidia were removed and transferred to fresh
potato dextrose agar (PDA) plate. Specimens and isolates of the new species have been
deposited in the Museum of Beijing Forestry University (BJFC). Axenic cultures are
maintained in the China Forestry Culture Collection Center (CFCC).
Morphological analysis
Morphological observations of the sexual and asexual morph in the natural environ-
ment were based on features of the fruiting bodies produced on infected plant tissues
and micromorphology, supplemented by cultural characteristics. Gross morphology of
fruiting bodies was recorded using a Leica stereomicroscope (M205 FA). Perithecia,
Nectria-related fungi causing dieback and canker diseases in China ... 51
pycnidia, synnemata and stromata were observed and described. To test ascomatal wall
reactions, 3% KOH and 100% lactic acid (LA) were used. e micromorphological
characteristics were examined by mounting fungal structures in clear lactic acid and
30 measurements at 1000× magnication were determined for each isolate using a
Leica compound microscope (DM 2500) with dierential interference contrast (DIC)
optics. Colony characters and pigment production on PDA were noted after 10 d.
Colony colours were described according to Rayner (1970). Longitudinal descriptions,
nomenclature and illustrations of taxonomic novelties are deposited in MycoBank
(http://www.MycoBank.org; Crous et al. 2004).
DNA extraction, PCR amplification and sequencing
Genomic DNA was extracted from colonies grown on cellophane-covered PDA,
using a modied CTAB [cetyltrimethylammonium bromide] method (Doyle and
Doyle 1990, Zhang et al. 2010). For PCR amplications of phylogenetic markers,
four dierent primer pairs were used (Table 1). PCR amplication products were as-
sayed via electrophoresis in 2% agarose gels. DNA sequencing was performed using
an ABI PRISM 3730XL DNA Analyzer with a BigDye Terminater Kit v.3.1 (Invit-
rogen, USA) at the Shanghai Invitrogen Biological Technology Company Limited
(Beijing, China).
Phylogenetic analyses
e quality of our amplied nucleotide sequences was checked and combined by Se-
qMan v.7.1.0 and reference sequences were retrieved from the National Center for
Biotechnology Information (NCBI), according to recent publications of the family
Nectriaceae (Jaklitsch and Voglmayr 2014, Lombard et al. 2015, Crous et al. 2016,
Yang et al. 2018). Sequences were aligned using MAFFT v. 7.310 (http://mat.cbrc.
jp/alignment/server/index.html) (Katoh and Standley 2016) and manually corrected
using Bioedit 7.0.9.0 (Hall 1999).
Phylogenetic analyses of the combined gene regions were performed using Maxi-
mum Parsimony (MP), Maximum-Likelihood (ML) and Bayesian Inference (BI)
methods. e data were edited in AliView version: 1.19-beta1k and the evolutionary
model obtained using MrModeltest v. 2.3 (Nylander et al. 2008) under the Akaike
Table 1. Genes used in this study with PCR primers, process and references.
Gene PCR primers (forward/reverse) PCR: thermal cycles: (Annealing temp. in bold) References of primers used
ITS ITS1/ITS4 (95 °C: 30 s, 51 °C: 30 s, 72 °C: 1 min) × 35 cycles White et al. 1990
LSU LROR/ LR5 (95 °C: 45 s, 55 °C: 45 s, 72 °C: 1 min) × 35 cycles Vilgalys and Hester 1990, Rehner and
Samuels 1994
tef1 EF1-728F and EF-1567R (95 °C: 15 s, 55 °C: 20 s, 72 °C: 1 min) × 35 cycles Carbone and Kohn 1999, Rehner 2001
tub2 T1/T2 (95 °C: 30 s, 55 °C: 30 s, 72 °C: 1 min) × 35 cycles O’Donnell and Cigelnik 1997
Qin Yang et al. / MycoKeys 56: 49–66 (2019)
52
Information Criterion (AIC) performed in PAUP v. 4.0b10. e MP analysis was
performed by a heuristic search option of 1000 random-addition sequences with a tree
bisection and reconnection (TBR) algorithm. Maxtrees were set to 5000, branches of
zero length were collapsed and all equally parsimonious trees were saved. Other calcu-
lated parsimony scores were tree length (TL), consistency index (CI), retention index
(RI) and rescaled consistency (RC). ML was performed using RAxML-HPC v.8 on
XSEDE in CIPRES Science Gateway (Miller et al. 2010, 2015, Stamatakis 2014) with
1000 rapid bootstrap replicates using the GTR+I+G model of nucleotide substitution.
BI was implemented by MrBayes v. 3.0b4 (Ronquist and Huelsenbeck 2003) with
GTR+I+G as the best-t model. Posterior Probabilities (PP) were estimated by Markov
Chain Monte Carlo sampling (MCMC) in MrBayes v. 3.0b4 (Huelsenbeck and Ron-
quist 2001). Two MCMC chains, started from random trees for 1,000,000 generations
and trees, were sampled every 100th generation, resulting in a total of 10,000 trees.
e rst 25% of trees were discarded as the burn-in phase of each analysis. Branches
with signicant Bayesian Posterior Probabilities (BPP) were estimated in the remain-
ing 7500 trees. Phylogenetic trees were viewed with FigTree v.1.3.1 (Rambaut and
Drummond 2010) and processed by Adobe Illustrator CS5. Alignment and trees were
deposited in TreeBASE (submission ID: 24366). e nucleotide sequence data of the
new taxon have been deposited in GenBank (Table 1).
Results
Phylogenetic analyses
To reveal the phylogenetic position amongst Nectria, Neothyronectria and yronectria
in Nectriaceae, a phylogenetic analysis was performed with combined ITS, LSU, tef1
and tub2 sequence data. Sequences of representative species were selected from NCBI
(Jaklitsch and Voglmayr 2014, Crous et al. 2016, Yang et al. 2018). e ITS, LSU,
tef1, tub2 and combined data matrices contained 545, 781, 1033, 643 and 3010 char-
acters with gaps, respectively. e alignment comprised 59 strains and Emericellopsis
glabra (CBS 125295), Hydropisphaera fungicola (CSB 122304), Nectriopsis exigua (CBS
126110) and Verrucostoma freycinetiae (MAFF 240100) were selected as the outgroups.
e concatenated sequence alignment contained 932 parsimony-informative char-
acters, 259 were variable and parsimony uninformative and 1819 were constant. e
parsimony analysis yielded the maximum of 10 equally most parsimonious trees (TL =
5493 steps; CI = 0.386; RI = 0.685; RC = 0.264; HI = 0.614).
e phylogeny, resulting from the MP analysis of combined gene sequence data,
is shown in Fig. 1. Overall, the topologies obtained from the dierent phylogenetic
analyses were mostly similar and the best scoring MP tree is illustrated here. e MP
and ML bootstrap support values above 50% are shown at the rst and second posi-
tion, respectively. Branches with signicant BPP (≥ 0.95) in Bayesian analyses were
thickened in the phylogenetic tree.
Nectria-related fungi causing dieback and canker diseases in China ... 53
Table 2. Strains and GenBank accession numbers of the isolates used in this study.
Species Isolate No. Substrate/Host Country GenBank Accession No.
ITS LSU tef1 tub2
Allantonectria miltina CBS 121121 Agave americana Italy HM484547 HM484572 HM484524 HM484609
Emericellopsis glabra CBS 125295 Soil Mexico HM484860 GQ505993 HM484843 HM484879
Hydropisphaera fungicola CBS 122304 Decaying leaves on
Populus trichocarpa
USA HM484863 GQ505995 HM484845 HM484877
N. antarctica CBS 115033 Berberis aquifolium USA HM484556 HM484560 HM484516 HM484601
N. asiatica MAFF 241439 Bark of dead wood Japan HM484701 HM484563 –HM484604
N. aurantiaca CBS 308.34 Ulmus sp. UK JF832628 JF832682 JF832519 JF832886
N. balansae CBS 123351 Coronilla sp. France HM484552 GQ505996 HM484525 HM484607
N. balansae CBS 129349 Twigs China JF832653 JF832711 JF832522 JF832908
N. berberidicola CBS 128669 Berberis vulgaris France JF832662 JF832712 JF832538 JF832887
N. cinnabarina CBS 125165 Dead twigs of
Aesculus sp.
France HM484548 HM484562 HM484527 HM484606
N. dematiosa Subclade A CBS 126570 Bark USA HM484557 HM484561 HM484534 HM484603
N. dematiosa Subclade A CFCC 53585 Tilia mandshurica China MK861084 MK861075 MK902792 MK902801
N. dematiosa Subclade A CFCC 53586 Betula platyphylla China MK861085 MK861076 MK902793 MK902802
N. dematiosa Subclade B CBS 125125 Dead twigs of Acer
macrophyllum
Canada HM484676 HM484717 HM484645 HM484797
N. eustromatica CBS 121896 – – HM534896 HM534896 HM534875 –
N. eustromatica CBS 125578 – – HM534897 HM534897 HM534876 –
N. magnispora CBS 129362 – Japan JF832663 JF832683 JF832539 JF832896
N. magnispora CBS 129361 Twigs Japan JF832664 JF832685 JF832540 JF832897
N. mariae CBS 125294 Buxus sempervirens France JF832629 JF832684 JF832542 JF832899
N. nigrescens CBS 125148 Dead twigs of
dicotyledonous tree
USA HM484707 HM484720 HM484672 HM484806
N. nigrescens CBS 128988 Elaeagnus
angustifolia
USA JF832630 JF832687 –JF832888
N. nigrescens CBS 129808 Ulmus pumila USA JF832632 JF832690 –JF832894
N. polythalama CBS 128672 Twigs New
Zealand
JF832638 JF832695 JF832523 JF832900
N. pseudocinnabarina CBS 129366 Dead wood Venezuela JF832642 JF832697 JF832533 –
N. pseudotrichia CBS 551.84 Bark Japan HM484554 GQ506000 HM484532 HM484602
N. pseudotrichia MAFF 241452 Bark Japan JF832649 JF832706 JF832531 JF832903
N. pseudotrichia G.J.S. 09-1329 Dead wood Venezuela JF832647 JF832702 JF832530 JF832902
N. pseudotrichia CFCC 53587 Robinia sp.China MK861086 MK861077 MK902794 MK902803
N. pseudotrichia CFCC 53588 Cinnamomum
porrectum
China MK861087 MK861078 MK902795 MK902804
N. pseudotrichia CFCC 53589 Rubus
corchorifolius
China MK861088 MK861079 MK902796 MK902805
N. sordida CBS 125119 Living woody vine French
Guiana
HM484857 HM484868 HM484848 HM484874
N. triseptata HAMS 252485 On rotten twig China KM026503 KM026504 KM026506 KM026501
N. ulmicola CFCC 52117 Ulmus davidiana
var. japonica
China MG231959 MG231980 MG232022 MG232043
N. ulmicola CFCC 52118 Ulmus davidiana
var. japonica
China MG231960 MG231981 MG232023 MG232044
Nectriopsis exigua CBS 126110 Myxomycete Puerto
Rico
HM484865 GQ506014 HM484852 HM484883
Neothyronectria citri CFCC 53590 Citrus maxima cv.
Shatian
China MK861080 MK861071 MK902788 MK902797
N. citri CFCC 53591 Citrus maxima c v.
Shatian
China MK861081 MK861072 MK902788 MK902798
N. sophorae CBS 142094 Sophora microphylla Zew
Zealand
KY173470 KY173559 –KY173619
yronectria aquifolii CBS 307.34 Ilex aquifolium UK JF832597 JF832718 JF832548 JF832842
Qin Yang et al. / MycoKeys 56: 49–66 (2019)
54
Figure 1. Maximum parsimony phylogenetic tree generated from analysis of a combined ITS, LSU, tef1
and tub2 sequence dataset for 59 taxa of Allantonectria, Nectria, Neothyronectria and yronectria. Emeri-
cellopsis glabra (CBS 125295), Hydropisphaera fungicola (CSB 122304), Nectriopsis exigua (CBS 126110)
and Verrucostoma freycinetiae (MAFF 240100) as outgroup taxa. Values above the branches indicate maxi-
mum parsimony and maximum likelihood bootstrap (left, MP BP ≥ 50%; right, ML BP ≥ 50%). e
branches with signicant BIPP values (≥ 0.95) in the BI analysis are thickened. Scale bar = 80 nucleotide
substitutions. Strains in current study are in blue. Ex-type strains are indicated in bold.
Nectria-related fungi causing dieback and canker diseases in China ... 55
Taxonomy
Nectria (Fr.) Fr., Summa veg. Scand., Sectio Post. (Stockholm): 387, 1849
Type species. Nectria cinnabarina (Tode) Fr., Summa veg. Scand., Sectio Post. (Stock-
holm): 388, 1849.
Note. Members of Nectria are typically weak parasites of woody plants and occur
on hardwood trees and shrubs throughout the temperate zone of the northern hemi-
sphere (Samuels et al. 2009, Hirooka et al. 2011). e genus Nectria is characterised by
well-developed stromata, subglobose to globose, red to dark red, eshy, soft-textured,
uniloculate, warted perithecia that become cupulate when dry and are associated with
coelomycetous asexual morphs. Asci are unitunicate and clavate to cylindrical in shape.
Ascospores are variable and usually broadly ellipsoid to long-fusiform, hyaline to yel-
low brown, smooth to striate and non- to multi-septate or muriform (Rossman et al.
1999, Hirooka et al. 2009, Maharachchikumbura et al. 2015).
Nectria dematiosa (Schwein.) Berk., Grevillea 4: 16, 1875
Fig. 2
Description. See Yang et al. (2018)
Additional specimens examined. CHINA. Heilongjiang Province, Liangshui
Nature Reserve, 47°10'50.64"N, 128°53'41.03"E, on twigs or branches of Tilia man-
dshurica Rmpr.et Maxim., 29 July 2016, Q. Yang (BJFC-S1400, living culture CFCC
53585); Xinjiang, 45°13'07.97"N, 81°46'24.71"E, on twigs or branches of Betula
platyphylla Suk., 18 July 2017, C.M. Tian (BJFC-S1767, living culture CFCC 53586).
Note. Nectria dematiosa has a broad host range and is widely distributed in China,
occurring as the most commonly Nectria species (Yang et al. 2018). is study is the
rst report of N. dematiosa from Betula platyphylla and Tilia mandshurica.
Nectria pseudotrichia Berk. & M.A. Curtis, J. Acad. Nat. Sci. Philadelphia 2, 2:
289. 1853
Fig. 3
Description. See Yang et al. (2018)
Additional specimens examined. CHINA. Shaanxi Province, Ankang City,
32°40'32.85"N, 109°18'57.38"E, on twigs or branches of Robinia sp., 29 July 2016,
N. Jiang (BJFC-S1403, living culture CFCC 53587); Jiangxi Province, Ganzhou
City, 24°40'51.80"N, 115°31'49.99"E, on twigs or branches of Cinnamomum por-
rectum (Roxb.) Kosterm., 12 May 2018, Q. Yang (BJFC-S1768, living culture CFCC
53588); Jiangxi Province, Ganzhou City, 24°59'44.81"N, 115°30'58.85"E, on twigs
or branches of Rubus corchorifolius Linn. f., 12 May 2018, Q. Yang (BJFC-S1769, liv-
ing culture CFCC 53589).
Qin Yang et al. / MycoKeys 56: 49–66 (2019)
56
Note. Nectria pseudotrichia is one of the common tropical fungi in the genus Nec-
tria and is distinguished in the genus by having muriform ascospores and a synnema-
tous asexual morph.
Neothyronectria Crous & angavel, Persoonia 37: 329, 2016.
Type species. NeothyronectriasophoraeCrous & angavel,Persoonia37: 329, 2016.
Note. e genus Neothyronectria was described by Crous & angavel (2016)
based on the only species, N.sophorae, which is known from a pycnidial asexual morph.
Neothyronectria is characterised by pycnidial conidiomata that exude a creamy mucoid
conidial mass and hyaline, ampulliform to subcylindrical conidia. In this study, we
collected and illustrated here one additional taxon inNeothyronectria.
Neothyronectria citri C.M. Tian & Q. Yang, sp. nov.
MycoBank: MB830779
Figure 4
Diagnosis. Neothyronectria citri diers from its closest phylogenetic neighbour
Neothyronectriasophorae in ITS, LSU and tub2 loci, based on the alignments deposited
in TreeBASE.
Holotype. CHINA. Jiangxi Province: Ganzhou city, 25°51'27.87"N,
114°58'18.95"E, on symptomatic branches of Citrus maxima (Burm.) Merr. cv. Sha-
tian Yu, 11 May 2018, Q. Yang, Y.M. Liang & Y. Liu (holotype BJFC-S1770 desig-
nated here, ex-type culture CFCC 53590).
Etymology. Named after the host genus on which it was collected, Citrus.
Description. Mycelium not visible around ascomata or on the host. Stromata
erumpent through epidermis, up to 0.6 mm high and 1 mm diam., pseudoparen-
chymatous, cells forming textura angularis to t. globulosa, intergrading with asco-
matal wall. Ascomata supercial on well-developed stromata, scattered to aggregated
in groups of 3–10, subglobose to globose, 200–270 μm diam., rarely slightly cupu-
late upon drying, sometimes with only a depressed apical region, yellowish-brown to
grey, apical region slightly darker, no colour change in KOH or LA, sometimes sur-
face scurfy or scaly, bright yellow to greenish-yellow. Ascomatal surface cells forming
textura globulosa or t. angularis, sometimes including bright yellow scurf, 9–15 μm
diam., walls pigmented, uniformly about 1.5 μm thick. Ascomatal wall 27–46 μm
thick, of two regions: outer region 22–35 μm thick, intergrading with stroma, cells
forming textura globulosa or t. angularis, walls pigmented, about 1.5 μm thick; inner
region 9–15 μm thick, of elongate, thin-walled, hyaline cells, forming textura pris-
matica. Asci clavate, unitunicate, 53.5–65 × 8.5–11 μm, with inconspicuous ring at
apex, 4-spored. Ascospores allantoid to short-cylindrical, uniseriate, rounded at both
Nectria-related fungi causing dieback and canker diseases in China ... 57
Figure 2. Nectria dematiosa (CFCC 53585) A–B habit of conidiomata on branches C transverse sec-
tion of conidioma D longitudinal section of conidioma E conidiophores F–G conidia. Scale bars: 1 mm
(A–C); 500 μm (D); 10 μm (E–G).
ends, (17–)18–21(–23.5) × 8–9(–10) μm (n = 20), muriform, hyaline to slightly
yellowish-brown.
Culture characters. Cultures incubated on PDA at 25 °C in darkness. Colony
originally at with white aerial mycelium, becoming pale yellowish due to pigment
formation, conidiomata absent.
Additional specimen examined. CHINA. Jiangxi Province: Ganzhou City,
25°51'27.87"N, 114°58'18.95"E, on symptomatic branches of Citrus maxima (Burm.)
Qin Yang et al. / MycoKeys 56: 49–66 (2019)
58
Merr. cv. Shatian Yu, 11 May 2018, Q. Yang, Y.M. Liang & Y. Liu (BJFC-S1771, liv-
ing culture CFCC 53591).
Note. Neothyronectria citri, as described here, is known from an ascomatal sexual
morph phylogenetically allied to species of Allantonectria and yronectria (Fig. 1).
In this study, two strains representing Neothyronectria citri cluster in a well-supported
clade and appear most closely related to Neothyronectriasophorae, which was isolated
from Sophora microphylla in New Zealand (Crous et al. 2016). Neothyronectria citri
can be distinguished, based on ITS, LSU and tub2 loci from Neothyronectriasophorae
(16/464 in ITS, 9/772 in LSU and 60/494 in tub2).
Figure 3. Nectria pseudotrichia (CFCC 53587) A–B habit of conidiomata on branches C–D conidi-
ophores E–F conidia. Scale bars: 1 mm (A–B); 10 μm (C–F).
Nectria-related fungi causing dieback and canker diseases in China ... 59
Figure 4. Neothyronectria citri (CFCC 53590) A–B habit of conidiomata on branches C transverse sec-
tion of conidioma D longitudinal section of conidioma E–F asci G–H ascospores. Scale bars: 500 μm
(B–D); 10 μm (E–H).
yronectriaSacc.,Grevillea4: 21, 1875.
Type species. yronectriarhodochlora(Mont.) Seeler,J. Arnold Arbor.21: 455, 1940.
Note. yronectria Sacc. was established by Saccardo (1875) to include nectria-like
fungi with immersed ascomata and muriform ascospores and characterised by well-
Qin Yang et al. / MycoKeys 56: 49–66 (2019)
60
developed erumpent stromata which are often covered with yellow-green amorphous
scurf and ascospores that sometimes bud in the ascus to produce ascoconidia (Jaklitsch
and Voglmayr 2014, Lombard et al. 2015). Members of the genus occur on dead
corticated twigs or branches of woody plants worldwide mainly in temperate and
subtropical regions (Hirooka et al. 2012, Jaklitsch and Voglmayr 2014).
yronectriapinicola(Kirschst.) Jaklitsch & Voglmayr,Persoonia33: 203, 2014.
Figure 5
Basionym. Pleonectria pinicola Kirschst., Abh. Bot. Ver. Prov. Brandenburg 48: 59,
1906.
Description. Stromata erumpent through epidermis, orange to red. Pycnidia
solitary or aggregated in groups of 3–6, supercial on stroma or rarely immersed at
base, subglobose, smooth to slightly roughened, cerebriformis or slightly cupulate upon
drying, 225–400 μm high, 240–440 μm diam., red to bay, KOH+ slightly darker, LA+
slightly yellow. Pycnidial wall 16–40 μm thick, of two regions: outer region 11–15 μm
thick, intergrading with stroma, cells forming textura globulosa or t. angularis, walls
pigmented, about 1.5 μm thick; inner region 10–24 μm thick, of elongate, thin-walled,
hyaline cells, forming textura prismatica. Conidiophores densely branched, generally
with 1–3 branches, 8.5–24 μm long, 1.3–1.5 μm wide. Conidiogenous cells cylindrical
monophialides on aerial, submerged or repent hyphae. Conidia formed abundantly on
slimy heads, ellipsoidal to oblong, hyaline, straight, rounded at both ends, non-septate,
(2–)3–3.5 × 0.7–1.0 μm (n = 20), smooth-walled.
Culture characters. Cultures incubated on PDA at 25 °C in darkness. Colony
surface cottony with aerial mycelium, becoming yellowish-brown due to pigment
formation, small reddish-brown sporodochial conidial masses produced after 3–4 wk.
Specimens examined. CHINA. Beijing: Chaoyang District, 40°00'35.31"N,
116°47'55.32"E, on symptomatic branches of Pinus sylvestris Linn. var. mongolica
Litv., 11 June 2018, Q. Yang & N. Jiang (BJFC-S1773, living culture CFCC 53593
and CFCC 53594).
Note. e hosts of yronectria pinicola, synonymised with Pleonectria pinicola,
are restricted to Pinus. Members of the genus distributed in Asia (China, Japan,
Pakistan), Australia, Europe (Germany, Russia), North America (USA) and South
America (Chile) (Jaklitsch and Voglmayr 2014). e asexual morph of T. pinicola in
the natural environment has long, sterile hyphae extending from the hymenium and
abundant conidiophores (Figs 4E–G). In the present study, two isolates from twigs
of Pinus sylvestris var. mongolica were congruent with T. pinicola, based on morphol-
ogy and DNA sequences data (Fig. 1). We therefore describe T. pinicola as a known
species for this clade.
Nectria-related fungi causing dieback and canker diseases in China ... 61
Figure 5. yronectria pinicola (CFCC 53593) A–C habit of conidiomata on branches D longitudinal
section of conidioma E–G conidiogenous cells with conidia H conidia I–J culture on PDA and conidi-
omata. Scale bars: 1 mm (B); 500 μm (C–D); 10 μm (E–H).
Qin Yang et al. / MycoKeys 56: 49–66 (2019)
62
Discussion
In this investigation of nectria-related fungi in China, we identied four species
in three genera (Nectria, Neothyronectria and yronectria) of Nectriaceae, based on
four combined loci (ITS, LSU, tef1 and tub2), as well as morphological characters.
It includes Nectria dematiosa, N. pseudotrichia, and yronectria pinicola as well as
one new species named Neothyronectria citri. e new species is characterised by
well-developed erumpent stromata that are often covered with yellow-green amor-
phous scurf; asci unitunicate, clavate, with inconspicuous ring at apex, each with
4-spored; ascospores allantoid to short-cylindrical, uniseriate, muriform, hyaline to
slightly yellowish.
Species revised by Rossman et al. (1999) in Nectria were monographed by Hirooka
et al. (2012), who recognised three genera, i.e. Allantonectria, Nectria and Pleonec-
tria. Allantonectria, based on Allantonectria miltina, was recognised as a monotypic
genus with small, aseptate ascospores, trichoderma-like conidiophores and occurring
on monocotyledonous plants. e genus yronectria (as Pleonectria) is characterised
by having ascomata with bright yellow scurf, ascospores that often bud to produce
ascoconidia inside or outside of the asci and/or a pycnidial anamorph (Hirooka et al.
2012). Based on the lack of bright yellowish scurf on the ascomata, the genus Nectria is
easily distinguished from Allantonectria and yronectria. In this study, Neothyronectria
citri was identied as a new species in Neothyronectria, which was typied by Neothy-
ronectriasophoraehaving ampulliform to subcylindrical conidia (Crous et al. 2016).
Unlike species of yronectria, Neothyronectria did not produce ascoconidia but they
have bright yellow scurf on the ascomatal wall.
In the taxonomy of hypocrealean fungi, the reaction of the perithecial wall to
KOH is considered as an important character (Rossman et al. 1999, Zeng and Zhuang
2016). Most species of Allantonectria and yronectria have perithecial colour turning
darker to blood-red or purple in KOH. However, some species in yronectria display a
weak or negative reaction to KOH, which might be inuenced by the presence of scurf
covering the perithecia or their dark-coloured ascomata (Hirooka et al. 2012, Jaklitsch
and Voglmayr 2014, Zeng and Zhuang 2016). In our study, the dark perithecial walls
of Neothyronectria citri do not change colour in KOH but the major features, such
well-developed stromata and ascomata with bright yellow scurf, as well as the molecu-
lar data, also provide strong evidence that it belongs to Neothyronectria.
Acknowledgements
is study is nanced by National Natural Science Foundation of China (Project No.:
31670647). We are grateful to Chungen Piao, Minwei Guo (China Forestry Culture
Collection Center (CFCC), Chinese Academy of Forestry, Beijing.
Nectria-related fungi causing dieback and canker diseases in China ... 63
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