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Research Article
Three new Diaporthe species from Shaanxi Province, China
expand article infoQin Yang§, Ning Jiang, Cheng-Ming Tian
‡ Beijing Forestry University, Beijing, China
§ Central South University of Forestry and Technology, Changsha, China
Open Access

Abstract

Diaporthe species (Sordariomycetes, Diaporthales) are often reported as important plant pathogens, saprobes and endophytes on a wide range of plant hosts. In this study, Diaporthe specimens were collected from symptomatic twigs and branches at the Huoditang Forest Farm in Shaanxi Province, China. Identification was done using a combination of morphology and comparison of DNA sequence data of the nuclear ribosomal internal transcribed spacer (ITS), calmodulin (cal), histone H3 (his3), partial translation elongation factor-1α (tef1) and β-tubulin (tub2) gene regions. Three new Diaporthe species are proposed: D. albosinensis, D. coryli and D. shaanxiensis. All species are illustrated and their morphology and phylogenetic relationships with other Diaporthe species are discussed.

Keywords

Diaporthaceae, Dieback, DNA phylogeny, Systematics, Taxonomy

Introduction

Diaporthe species (Sordariomycetes, Diaporthales) are associated with a wide range of plant hosts as pathogens, endophytes or saprobes of crops, ornamentals and forest trees (Murali et al. 2006, Rossman et al. 2007, Garcia-Reyne et al. 2011, Gomes et al. 2013, Udayanga et al. 2015, Dissanayake et al. 2017, Guarnaccia and Crous 2017, 2018, Wijayawardene et al. 2017, Yang et al. 2017a, b, 2018, Fan et al. 2018, Guarnaccia et al. 2018). The sexual morph of Diaporthe is characterised by immersed ascomata and an erumpent pseudostroma with elongated perithecial necks. Asci are unitunicate, clavate to cylindrical. Ascospores are fusoid, ellipsoid to cylindrical, hyaline, biseriate to uniseriate in the ascus, sometimes with appendages (Udayanga et al. 2011). The asexual morph is characterised by ostiolate conidiomata, with cylindrical phialides producing three types of hyaline, aseptate conidia (Udayanga et al. 2011, Gomes et al. 2013).

Species identification in Diaporthe has traditionally been based on host association, morphology and culture characteristics (Mostert et al. 2001, Santos and Phillips 2009, Udayanga et al. 2011), resulting in the description of over 200 species (Hyde et al. 2020). Multiple species of Diaporthe can colonise a single host and one species can be associated with different hosts (Santos and Phillips 2009, Diogo et al. 2010, Santos et al. 2011, Gomes et al. 2013). In addition, considerable within-species variability of phenotypic characters has been reported (Rehner and Uecker 1994, Mostert et al. 2001, Udayanga et al. 2011). Thus, a polyphasic taxonomic approach, based on multi-locus DNA data, morphology and ecology, has been increasingly employed for species boundaries in the genus Diaporthe (Gomes et al. 2013, Huang et al. 2013, 2015, Udayanga et al. 2014a, b, 2015, Fan et al. 2015, Du et al. 2016, Gao et al. 2016, 2017, Guarnaccia and Crous 2017, Guarnaccia et al. 2018, Long et al. 2019).

Huoditang is located in the middle part of the southern slope of the Qinling Mountains at 33°18'~33°28'N, 108°21'~108°29'E. It belongs to the transitional zone of the northern subtropical and warm temperate zone in China. The terrain is complex and the climate is changeable (Zhang and Cao 2007). The plant communities are complex and, as a result, species diversity of fungi in the forest area is high (Zhang and Cao 2007). During trips to collect forest pathogens causing dieback in Shaanxi Province, cankered branches with typical Diaporthe fruiting bodies were investigated and sampled. The aim of the present study was to identify these fungi, based on modern polyphasic taxonomic concepts.

Materials and methods

Isolates

Fresh specimens of Diaporthe were collected from symptomatic twigs or branches in Shaanxi Province (Table 1). Isolates were obtained by removing a mucoid spore mass from conidiomata and spreading the suspension on the surface of 1.8% potato dextrose agar (PDA) in a 9 cm diam. Petri dish. Petri dishes were incubated at 25 °C until spores germinated. Single germinating conidia were transferred on to new PDA plates, which were kept at 25 °C in the dark. Specimens are deposited in the Museum of the Beijing Forestry University (BJFC). Axenic cultures are maintained in the China Forestry Culture Collection Centre (CFCC).

Morphological analysis

Morphological observations of the asexual morph in the natural environment were based on features of the fruiting bodies produced on infected plant tissues and micromorphology, supplemented by cultural characteristics. Conidiomata from tree barks were sectioned by hand, using a double-edged blade and structures were observed under a dissecting microscope. The gross morphology of fruiting bodies was recorded using a Leica stereomicroscope (M205 FA). Fungal structures were mounted in clear lactic acid and micromorphological characteristics were examined at 1000× magnification using a Leica compound microscope (DM 2500) with differential interference contrast (DIC) optics. Thirty measurements of each structure were determined for each collection. Colony characters and pigment production on PDA were noted after 10 d. Colony colours were described according to Rayner (1970).

DNA extraction, PCR amplification and sequencing

Genomic DNA was extracted from colonies grown on cellophane-covered PDA, using the CTAB [cetyltrimethylammonium bromide] method (Doyle and Doyle 1990). PCR amplifications of phylogenetic markers were done using the same primer pairs and conditions as in Yang et al. (2018). PCR products were assayed 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 (Invitrogen, USA) at the Shanghai Invitrogen Biological Technology Company Limited (Beijing, China).

Phylogenetic analyses

The quality of our amplified nucleotide sequences was checked and combined by SeqMan v.7.1.0 and reference sequences were retrieved from the National Center for Biotechnology Information (NCBI), based on recent publications on the genus Diaporthe (Guarnaccia et al. 2018, Yang et al. 2018, Long et al. 2019). Sequences were aligned using MAFFT v. 7.310 (http://mafft.cbrc.jp/alignment/server/index.html) (Katoh and Standley 2016) and manually corrected using Bioedit 7.0.9.0 (Hall 1999). The best-fit nucleotide substitution models for each gene were selected using jModelTest v. 2.1.7 (Darriba et al. 2012) under the Akaike Information Criterion.

Phylogenetic analyses of the combined gene regions were performed using Maximum-Likelihood (ML) and Bayesian Inference (BI) methods. ML was conducted using PhyML v. 3.0 (Guindon et al. 2010), with 1000 bootstrap replicates. BI was performed using a Markov Chain Monte Carlo (MCMC) algorithm in MrBayes v. 3.0b4 (Ronquist and Huelsenbeck 2003). 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. The first 25% of trees were discarded as burn-in of each analysis. Branches with significant Bayesian Posterior Probabilities (BPP) were estimated in the remaining 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: S25522). The nucleotide sequence data of the new taxa have been deposited in GenBank (Table 1).

Table 1.

Isolates and GenBank accession numbers used in the phylogenetic analyses of Diaporthe.

Species Isolate Host Location GenBank accession numbers
ITS cal his3 tef1 tub2
D. acericola MFLUCC 17-0956 Acer negundo Italy KY964224 KY964137 NA KY964180 KY964074
D. acerigena CFCC 52554 Acer tataricum China MH121489 MH121413 MH121449 MH121531 NA
D. albosinensis CFCC 53066 Betula albosinensis China MK432659 MK442979 MK443004 MK578133 MK578059
CFCC 53067 Betula albosinensis China MK432660 MK442980 MK443005 MK578134 MK578060
D. alnea CBS 146.46 Alnus sp. Netherlands KC343008 KC343250 KC343492 KC343734 KC343976
D. ambigua CBS 114015 Pyrus communis South Africa KC343010 KC343252 KC343494 KC343736 KC343978
D. anacardii CBS 720.97 Anacardium occidentale East Africa KC343024 KC343266 KC343508 KC343750 KC343992
D. angelicae CBS 111592 Heracleum sphondylium Austria KC343027 KC343269 KC343511 KC343753 KC343995
D. apiculatum CGMCC 3.17533 Camellia sinensis China KP267896 NA NA KP267970 KP293476
D. aquatica IFRDCC 3051 Aquatic habitat China JQ797437 NA NA NA NA
D. arctii CBS 139280 Arctium lappa Austria KJ590736 KJ612133 KJ659218 KJ590776 KJ610891
D. aseana MFLUCC 12-0299a Unknown dead leaf Thailand KT459414 KT459464 NA KT459448 KT459432
D. asheicola CBS 136967 Vaccinium ashei Chile KJ160562 KJ160542 NA KJ160594 KJ160518
D. baccae CBS 136972 Vaccinium corymbosum Italy KJ160565 NA MF418264 KJ160597 NA
D. beilharziae BRIP 54792 Indigofera australis Australia JX862529 NA NA JX862535 KF170921
D. benedicti BPI 893190 Salix sp. USA KM669929 KM669862 NA KM669785 NA
D. betulae CFCC 50469 Betula platyphylla China KT732950 KT732997 KT732999 KT733016 KT733020
D. betulina CFCC 52560 Betula albo-sinensis China MH121495 MH121419 MH121455 MH121537 MH121577
D. bicincta CBS 121004 Juglans sp. USA KC343134 KC343376 KC343618 KC343860 KC344102
D. caryae CFCC 52563 Carya illinoensis China MH121498 MH121422 MH121458 MH121540 MH121580
D. cassines CPC 21916 Cassine peragua South Africa KF777155 NA NA KF777244 NA
D. celeris CPC 28262 Vitis vinifera Czech Republic MG281017 MG281712 MG281363 MG281538 MG281190
D. cercidis CFCC 52565 Cercis chinensis China MH121500 MH121424 MH121460 MH121542 MH121582
D. chamaeropis CBS 454.81 Chamaerops humilis Greece KC343048 KC343290 KC343532 KC343774 KC344016
D. charlesworthii BRIP 54884m Rapistrum rugostrum Australia KJ197288 NA NA KJ197250 KJ197268
D. chensiensis CFCC 52567 Abies chensiensis China MH121502 MH121426 MH121462 MH121544 MH121584
D. cichorii MFLUCC 17-1023 Cichorium intybus Italy KY964220 KY964133 NA KY964176 KY964104
D. cinnamomi CFCC 52569 Cinnamomum sp. China MH121504 NA MH121464 MH121546 MH121586
D. citriasiana CGMCC 3.15224 Citrus unshiu China JQ954645 KC357491 KJ490515 JQ954663 KC357459
D. citrichinensis CGMCC 3.15225 Citrus sp. China JQ954648 KC357494 NA JQ954666 NA
D. compactum CGMCC 3.17536 Camellia sinensis China KP267854 NA KP293508 KP267928 KP293434
D. conica CFCC 52571 Alangium chinense China MH121506 MH121428 MH121466 MH121548 MH121588
D. coryli CFCC 53083 Corylus mandshurica China MK432661 MK442981 MK443006 MK578135 MK578061
CFCC 53084 Corylus mandshurica China MK432662 MK442982 MK443007 MK578136 MK578062
D. cucurbitae CBS 136.25 Arctium sp. Unknown KC343031 KC343273 KC343515 KC343757 KC343999
D. cuppatea CBS 117499 Aspalathus linearis South Africa KC343057 KC343299 KC343541 KC343783 KC344025
D. cynaroidis CBS 122676 Protea cynaroides South Africa KC343058 KC343300 KC343542 KC343784 KC344026
D. cytosporella FAU461 Citrus limon Italy KC843307 KC843141 NA KC843116 KC843221
D. discoidispora ZJUD89 Citrus unshiu China KJ490624 NA KJ490566 KJ490503 KJ490445
D. dorycnii MFLUCC 17-1015 Dorycnium hirsutum Italy KY964215 NA NA KY964171 KY964099
D. elaeagni-glabrae CGMCC 3.18287 Elaeagnus glabra China KX986779 KX999281 KX999251 KX999171 KX999212
D. endophytica CBS 133811 Schinus terebinthifolius Brazil KC343065 KC343307 KC343549 KC343791 KC343065
D. eres AR5193 Ulmus sp. Germany KJ210529 KJ434999 KJ420850 KJ210550 KJ420799
D. eucalyptorum CBS 132525 Eucalyptus sp. Australia NR120157 NA NA NA NA
D. foeniculacea CBS 123208 Foeniculum vulgare Portugal KC343104 KC343346 KC343588 KC343830 KC344072
D. fraxini-angustifoliae BRIP 54781 Fraxinus angustifolia Australia JX862528 NA NA JX862534 KF170920
D. fraxinicola CFCC 52582 Fraxinus chinensis China MH121517 MH121435 NA MH121559 NA
D. fructicola MAFF 246408 Passiflora edulis × P. edulis f. flavicarpa Japan LC342734 LC342738 LC342737 LC342735 LC342736
D. fusicola CGMCC 3.17087 Lithocarpus glabra China KF576281 KF576233 NA KF576256 KF576305
D. garethjonesii MFLUCC 12-0542a Unknown dead leaf Thailand KT459423 KT459470 NA KT459457 KT459441
D. guangxiensis JZB320094 Vitis vinifera China MK335772 MK736727 NA MK523566 MK500168
D. helicis AR5211 Hedera helix France KJ210538 KJ435043 KJ420875 KJ210559 KJ420828
D. heterophyllae CBS 143769 Acacia heterohpylla France MG600222 MG600218 MG600220 MG600224 MG600226
D. hubeiensis JZB320123 Vitis vinifera China MK335809 MK500235 NA MK523570 MK500148
D. incompleta CGMCC 3.18288 Camellia sinensis China KX986794 KX999289 KX999265 KX999186 KX999226
D. inconspicua CBS 133813 Maytenus ilicifolia Brazil KC343123 KC343365 KC343607 KC343849 KC344091
D. infecunda CBS 133812 Schinus terebinthifolius Brazil KC343126 KC343368 KC343610 KC343852 KC344094
D. juglandicola CFCC 51134 Juglans mandshurica China KU985101 KX024616 KX024622 KX024628 KX024634
D. kadsurae CFCC 52586 Kadsura longipedunculata China MH121521 MH121439 MH121479 MH121563 MH121600
D. litchicola BRIP 54900 Litchi chinensis Australia JX862533 NA NA JX862539 KF170925
D. lusitanicae CBS 123212 Foeniculum vulgare Portugal KC343136 KC343378 KC343620 KC343862 KC344104
D. masirevicii BRIP 57892a Helianthus annuus Australia KJ197277 NA NA KJ197239 KJ197257
D. middletonii BRIP 54884e Rapistrum rugostrum Australia KJ197286 NA NA KJ197248 KJ197266
D. millettiae GUCC9167 Millettia reticulata China MK398674 MK502086 NA MK480609 MK502089
D. miriciae BRIP 54736j Helianthus annuus Australia KJ197282 NA NA KJ197244 KJ197262
D. musigena CBS 129519 Musa sp. Australia KC343143 KC343385 KC343627 KC343869 KC344111
D. neilliae CBS 144.27 Spiraea sp. USA KC343144 KC343386 KC343628 KC343870 KC344112
D. neoarctii CBS 109490 Ambrosia trifida USA KC343145 KC343387 KC343629 KC343871 KC344113
D. nothofagi BRIP 54801 Nothofagus cunninghamii Australia JX862530 NA NA JX862536 KF170922
D. novem CBS 127270 Glycine max Croatia KC343155 KC343397 KC343640 KC343881 KC344123
D. oraccinii CGMCC 3.17531 Camellia sinensis China KP267863 NA KP293517 KP267937 KP293443
D. ovalispora ICMP20659 Citrus limon China KJ490628 NA KJ490570 KJ490507 KJ490449
D. ovoicicola CGMCC 3.17093 Citrus sp. China KF576265 KF576223 NA KF576240 KF576289
D. osmanthi GUCC9165 Osmanthus fragrans China MK398675 MK502087 NA MK480610 MK502090
D. padina CFCC 52590 Padus racemosa China MH121525 MH121443 MH121483 MH121567 MH121604
D. pandanicola MFLU 18-0006 Pandanus sp. Thailand MG646974 NA NA NA MG646930
D. pascoei BRIP 54847 Persea americana Australia JX862532 NA NA JX862538 KF170924
D. passifloricola CBS 141329 Passiflora foetida Malaysia KX228292 NA KX228367 NA KX228387
D. perseae CBS 151.73 Persea gratissima Netherlands KC343173 KC343415 KC343657 KC343899 KC344141
D. pescicola MFLUCC 16-0105 Prunus persica China KU557555 KU557603 NA KU557623 KU557579
D. phaseolorum AR4203 Phaseolus vulgaris USA KJ590738 NA KJ659220 NA KP004507
D. podocarpi-macrophylli CGMCC 3.18281 Podocarpus macrophyllus China KX986774 KX999278 KX999246 KX999167 KX999207
D. pseudomangiferae CBS 101339 Mangifera indica Dominican Republic KC343181 KC343423 KC343665 KC343907 KC344149
D. pseudophoenicicola CBS 462.69 Phoenix dactylifera Spain KC343184 KC343426 KC343668 KC343910 KC344152
D. psoraleae-pinnatae CBS 136413 Psoralea pinnata South Africa KF777159 NA NA NA KF777252
D. pulla CBS 338.89 Hedera helix Yugoslavia KC343152 KC343394 KC343636 KC343878 KC344120
D. racemosae CBS 143770 Euclea racemosa South Africa MG600223 MG600219 MG600221 MG600225 MG600227
D. ravennica MFLUCC 15-0479 Tamarix sp. Italy KU900335 NA NA KX365197 KX432254
D. rhusicola CBS 129528 Rhus pendulina South Africa JF951146 KC843124 NA KC843100 KC843205
D. rosae MFLU 17-1550 Rosa sp. Thailand MG828894 NA NA NA MG843878
D. rosicola MFLU 17-0646 Rosa sp. UK MG828895 NA NA MG829270 MG843877
D. rudis AR3422 Laburnum anagyroides Austria KC843331 KC843146 NA KC843090 KC843177
D. sackstonii BRIP 54669b Helianthus annuus Australia KJ197287 NA NA KJ197249 KJ197267
D. salicicola BRIP 54825 Salix purpurea Australia JX862531 NA NA JX862537 JX862531
D. sambucusii CFCC 51986 Sambucus williamsii China KY852495 KY852499 KY852503 KY852507 KY852511
D. schini CBS 133181 Schinus terebinthifolius Brazil KC343191 KC343433 KC343675 KC343917 KC344159
D. schoeni MFLU 15-1279 Schoenus nigricans Italy KY964226 KY964139 NA KY964182 KY964109
D. sennicola CFCC 51634 Senna bicapsularis China KY203722 KY228873 KY228879 KY228883 KY228889
D. serafiniae BRIP 55665a Helianthus annuus Australia KJ197274 NA NA KJ197236 KJ197254
D. shaanxiensis CFCC 53106 on branches of liana China MK432654 MK442976 MK443001 MK578130 NA
CFCC 53107 on branches of liana China MK432655 MK442977 MK443002 MK578131 NA
D. siamensis MFLUCC 10-573a Dasymaschalon sp. Thailand JQ619879 NA NA JX275393 JX275429
D. sojae FAU635 Glycine max USA KJ590719 KJ612116 KJ659208 KJ590762 KJ610875
D. sterilis CBS 136969 Vaccinium corymbosum Italy KJ160579 KJ160548 MF418350 KJ160611 KJ160528
D. stictica CBS 370.54 Buxus sampervirens Italy KC343212 KC343454 KC343696 KC343938 KC344180
D. subclavata ICMP20663 Citrus unshiu China KJ490587 NA KJ490529 KJ490466 KJ490408
D. subcylindrospora MFLU 17-1195 Salix sp. China MG746629 NA NA MG746630 MG746631
D. subellipicola MFLU 17-1197 on dead wood China MG746632 NA NA MG746633 MG746634
D. subordinaria CBS 464.90 Plantago lanceolata New Zealand KC343214 KC343456 KC343698 KC343940 KC344182
D. tectonendophytica MFLUCC 13-0471 Tectona grandis China KU712439 KU749354 NA KU749367 KU749354
D. tectonigena MFLUCC 12-0767 Tectona grandis China KU712429 KU749358 NA KU749371 KU743976
D. terebinthifolii CBS 133180 Schinus terebinthifolius Brazil KC343216 KC343458 KC343700 KC343942 KC344184
D. ternstroemia CGMCC 3.15183 Ternstroemia gymnanthera China KC153098 NA NA KC153089 NA
D. thunbergii MFLUCC 10-576a Thunbergia laurifolia Thailand JQ619893 JX197440 NA JX275409 JX275449
D. tibetensis CFCC 51999 Juglandis regia China MF279843 MF279888 MF279828 MF279858 MF279873
D. ueckerae FAU656 Cucumis melo USA KJ590726 KJ612122 KJ659215 KJ590747 KJ610881
D. ukurunduensis CFCC 52592 Acer ukurunduense China MH121527 MH121445 MH121485 MH121569 NA
D. unshiuensis CFCC 52594 Carya illinoensis China MH121529 MH121447 MH121487 MH121571 MH121606
D. vaccinii CBS 160.32 Oxycoccus macrocarpos USA KC343228 KC343470 KC343712 KC343954 KC344196
D. velutina CGMCC 3.18286 Neolitsea sp. China KX986790 NA KX999261 KX999182 KX999223
D. viniferae JZB320071 Vitis vinifera China MK341551 MK500107 NA MK500119 MK500112
D. xishuangbanica CGMCC 3.18282 Camellia sinensis China KX986783 NA KX999255 KX999175 KX999216
D. yunnanensis CGMCC 3.18289 Coffea sp. China KX986796 KX999290 KX999267 KX999188 KX999228
Diaporthella corylina CBS 121124 Corylus sp. China KC343004 KC343246 KC343488 KC343730 KC343972

Results

Phylogenetic analyses

The five-gene sequence dataset (ITS, cal, his3, tef1 and tub2) was analysed to infer the interspecific relationships within Diaporthe. The dataset consisted of 124 sequences including the outgroup, Diaporthella corylina (culture CBS 121124). A total of 2555 characters including gaps (505 for ITS, 513 for cal, 528 for his3, 475 for tef1 and 522 for tub2) were included in the phylogenetic analysis. The best nucleotide substitution model for ITS, his3 and tub2 was TrN+I+G, while HKY+I+G was selected for both cal and tef1. The topologies resulting from ML and BI analyses of the concatenated dataset were congruent (Fig. 1). Isolates from Shaanxi Province formed three individual clades representing three undescribed species.

Figure 1. 

Phylogram of Diaporthe resulting from a maximum likelihood analysis based on combined ITS, cal, his3, tef1 and tub2. Numbers above the branches indicate ML bootstraps (left, ML BS ≥ 50%) and Bayesian Posterior Probabilities (right, BPP ≥ 0.90). The tree is rooted with Diaporthella corylina. Isolates in current study are in blue. “-” indicates ML BS < 50% or BI PP < 0.90.

Taxonomy

Diaporthe albosinensis C.M. Tian & Q. Yang, sp. nov.

MycoBank No: 829518
Fig. 2

Diagnosis

Distinguished from D. fraxinicola in having shorter conidiophores and longer beta conidia.

Figure 2. 

Diaporthe albosinensis on Betula albosinensis (BJFC-S1670). A Habit of conidiomata in wood B transverse section of conidiomata C longitudinal section through conidiomata D conidiogenous cells attached with beta conidia E conidiogenous cells attached with alpha conidia F beta conidia. Scale bars: 200 μm (B–C); 20 μm (D, F); 10 μm (E).

Etymology

Named after the host plant, Betula albosinensis, from which the holotype was collected.

Description

Conidiomata pycnidial, conical, immersed in bark, solitary to aggregated, erumpent through the bark surface, with a solitary undivided locule. Ectostromatic disc yellowish to brown, one ostiole per disc. Ostiole medium black, up to the level of disc. Locule undivided, (280–)290–375(–380) μm diam. Conidiophores (6–)8.5–13(–14.5) × (1.5–)2–2.5 μm, hyaline, cylindrical, smooth, phialidic, unbranched, straight or slightly curved. Alpha conidia hyaline, aseptate, fusiform, 0–1-guttulate, (7–)8–10(–11) × 2.5–3 μm. Beta conidia hyaline, aseptate, filiform, straight or slightly curved, eguttulate, base subtruncate, tapering towards one apex, (24–)25.5–30(–32) × 1–1.5 µm.

Culture characters

Cultures incubated on PDA at 25 °C in the dark. Colony originally flat with white felted aerial mycelium, becoming light brown due to pigment formation, conidiomata irregularly distributed over agar surface, with yellowish conidial drops exuding from the ostioles.

Specimens examined

China. Shaanxi Province: Ningshan County, Huoditang Forest Farm, 33°28'25"N, 108°29'39"E, on branches of Betula albosinensis, 10 July 2018, N. Jiang (holotype BJFC-S1670; ex-type living culture: CFCC 53066; living culture: CFCC 53067).

Notes

Two isolates, representing D. albosinensis, are retrieved in a well-supported clade (ML BS/BPP=100/1) and appear most closely related to D. fraxinicola (Fig. 1). Diaporthe albosinensis can be distinguished from D. fraxinicola, based on tef1 and tub2 loci (3/335 in tef1 and 19/429 in tub2). Morphologically, D. albosinensis differs from D. fraxinicola in having shorter conidiophores (8.5–13 vs. 10.5–17.5 μm) and longer beta conidia (25.5–30 vs. 19–29.5 μm) (Yang et al. 2018).

Diaporthe coryli C.M. Tian & Q. Yang, sp. nov.

MycoBank No: 829520
Fig. 3

Diagnosis

Distinguished from D. ukurunduensis and D. citrichinensis in having larger alpha conidia.

Figure 3. 

Diaporthe coryli on Corylus mandshurica (BJFC-S1671). A, B Habit of conidiomata in wood C transverse section of conidiomata D longitudinal section through conidiomata E conidiogenous cells attached with alpha conidia F alpha conidia. Scale bars: 500 μm (B–D); 10 μm (E); 20 μm (F).

Etymology

Named after the genus of the host plant from which the holotype was collected, Corylus.

Description

Conidiomata pycnidial, conical to spherical, immersed in the host bark, erumpent from surface of host branches, scattered, 950–1200 × 420–650 μm diam., covered by orange discharged conidial masses at maturity, usually conspicuous. Ectostromatic disc inconspicuous. Central column beneath the disc more or less conical, bright yellow. Conidiophores reduced to conidiogenous cells. Conidiogenous cells cylindrical, hyaline, smooth, unbranched, tapering towards the apex, (8.5–)10–12(–13) × (2–)2.5–3 μm. Alpha conidia hyaline, aseptate, fusiform, multiguttulate, rarely 2-guttulate, (10.5–)11.5–13(–13.5) × 3–3.5 μm. Beta conidia not observed.

Culture characters

Cultures incubated on PDA at 25 °C in the dark. Colony flat, felty with thick texture at the marginal area, with thin texture in the centre, producing beige pigment after 7–10 d. Aerial mycelium white, dense, conidiomata distributed in the centre, with translucent conidial drops exuding from the ostioles.

Specimens examined

CHINA. Shaanxi Province: Ningshan County, Huoditang Forest Farm, 33°28'26"N, 108°29'40"E, on branches of Corylus mandshurica, 10 July 2018, N. Jiang (holotype BJFC-S1671; ex-type living culture: CFCC 53083); 33°28'26"N, 108°29'38"E, on branches of Corylus mandshurica, 10 July 2018, N. Jiang (paratype BJFC-S1672; living culture: CFCC 53084).

Notes

We generated sequences for two isolates of D. coryli, CFCC 53083 and CFCC 53084. This new species is phylogenetically most closely related to D. ukurunduensis and D. citrichinensis (Fig. 1). Diaporthe coryli can be distinguished from D. ukurunduensis, based on ITS, his3 and tef1 loci (8/467 in ITS, 1/460 in his3 and 1/336 in tef1); and from D. citrichinensis based on tef1 and tub2 loci (4/335 in tef1 and 25/428 in tub2). Morphologically, D. coryli can be distinguished from both D. ukurunduensis (11.5–13 × 3–3.5 vs. 5–6 × 2–3 μm) and D. citrichinensis (11.5–13 × 3–3.5 vs. 5.5–9 × 1.5–2.5 μm) in having larger alpha conidia (Huang et al. 2013, Gao et al. 2016).

Diaporthe shaanxiensis C.M. Tian & Q. Yang, sp. nov.

MycoBank No: 829527
Fig. 4

Diagnosis

Distinguished from D. aquatica and D. incompleta in having longer beta conidia.

Figure 4. 

Diaporthe shaanxiensis on liana (BJFC-S1674). A, B Habit of conidiomata on twig C transverse section through conidiomata D longitudinal section through conidiomata E conidiogenous cells attached with beta conidia F beta conidia. Scale bars: 200 μm (B–D); 10 μm (E, F).

Etymology

Named after Province Shaanxi, where the holotype was collected.

Description

Conidiomata pycnidial, immersed in bark, scattered, erumpent through the bark surface, discoid, with a solitary undivided locule. Ectostromatic disc yellowish to pale brown, one ostiole per disc, usually conspicuous, (485–)500–687(–695) μm diam. Locule circular, undivided, (500–)526–765(–792) μm diam. Conidiophores reduced to conidiogenous cells. Conidiogenous cells hyaline, cylindrical, unbranched, slightly curved, tapering towards the apex, (12.5–)14.5–17(–18) × 1–1.5(–2) μm. Alpha conidia not observed. Beta conidia hyaline, aseptate, filiform, straight to curved, eguttulate, (35.5–)37–47.5(–50) × 1 µm.

Culture characters

Cultures incubated on PDA at 25 °C in the dark. Colony originally flat with white fluffy aerial mycelium, becoming pale brown with pigment, with visible solitary conidiomata at maturity.

Specimens examined

CHINA. Shaanxi Province: Ningshan County, Huoditang Forest Farm, 33°28'25"N, 108°29'39"E, on branch of liana, 10 July 2018, N. Jiang (holotype BJFC-S1674; ex-type living culture: CFCC 53106); 33°28'24"N, 108°29'38"E, on branch of liana, 10 July 2018, N. Jiang (Paratype BJFC-S1675; living culture: CFCC 53107).

Notes

In the combined tree, D. shaanxiensis is a distinct clade with maximum support and it appears to be most closely related to D. aquatica and D. incompleta (Fig. 1). Diaporthe shaanxiensis can be distinguished from D. aquatica by a 17 nt difference in the ITS region. For D. aquatica, only ITS sequences are available in NCBI GenBank (Hu et al. 2012). The new species can be distinguished from D. incompleta, based on ITS, cal, his3 and tef1 (24/454 in ITS, 14/443 in cal, 66/468 in his3 and 24/311 in tef1). Morphologically, D. shaanxiensis differs from both D. aquatica (37–47.5 vs. 9–12.5 µm) and D. incompleta (37–47.5 vs. 19–44 µm) in having longer beta conidia (Gao et al. 2016, 2017).

Discussion

In this study, an investigation of forest pathogens from Huoditang in Shaanxi Province was carried out and Diaporthe canker was observed as a common disease. Identification of our collections was conducted, based on isolates from fruiting bodies using five combined loci (ITS, cal, his3, tef1 and tub2), as well as morphological characters. Three new Diaporthe species were described. These are D. albosinensis sp. nov., D. coryli sp. nov. and D. shaanxiensis sp. nov.

Diaporthe albosinensis is associated with Betula albosinensis. Thus far, six Diaporthe species have been reported from Betula. These are D. alleghaniensis, D. betulae, D. betulicola, D. betulina, D. eres and D. melanocarpa (Kobayashi 1970, Gomes et al. 2013, Du et al. 2016, Yang et al. 2018). Morphologically, D. albosinensis differs from D. betulae (600–1250 μm), D. betulicola (700–1300 μm) and D. betulina (670–905 μm) in having smaller locules (Du et al. 2016, Yang et al. 2018); and from D. alleghaniensis (5–8 × 1.5–2 μm) and D. eres (6.5–8.5 × 3–4 μm) in having larger alpha conidia (Arnold 1967, Anagnostakis 2007, Gomes et al. 2013). In addition, our phylogenetic reconstruction of a five-locus dataset adds support for the new species, although no sequence data are currently available for D. alleghaniensis, D. betulicola and D. melanocarpa (Fig. 1). Interestingly, D. melanocarpa is found on different plant hosts; it was described from Pyrus melanocarpa in London and then recorded from Amelanchier, Betula and Cornus (Dearness 1926, Wehmeyer 1933, Kobayashi 1970). Diaporthe coryli is characterised by the ostiole with orange discharged conidial masses and a yellow central column (Fig. 3). Diaporthe shaanxiensis was found on branches of liana with an obvious ostiole per disc and characterised by hyaline, filiform beta conidia. Alpha conidia were found neither in the natural environment nor in culture for this species.

Species delimitation of Diaporthe has improved considerably by using a combination of morphological, cultural, phytopathological and molecular phylogenetic analyses (Udayanga et al. 2014a, b, 2015, Fan et al. 2015, Gao et al. 2017, Guarnaccia and Crous 2017, Hyde et al. 2017, 2020, Guarnaccia et al. 2018, Yang et al. 2018, Long et al. 2019). As a result, many Diaporthe canker diseases and new species have been discovered and reported from all over the world and also in China. The descriptions and molecular data of Diaporthe species represent an important resource for plant pathologists, plant quarantine officials and taxonomists.

Acknowledgements

This study is financed by the Research Foundation of Education Bureau of Hunan Province, China (Project No.: 19B608) and the introduction of talent research start-up fund project of CSUFT (Project No.: 2019YJ025). We are grateful to Chungen Piao, Minwei Guo (China Forestry Culture Collection Center, Chinese Academy of Forestry, Beijing) and reviewers Lu Quan and Jadson Bezerra.

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