Research Article |
Corresponding author: Cheng-Ming Tian ( chengmt@bjfu.edu.cn ) Academic editor: Cecile Gueidan
© 2019 Ning Jiang, Xin-Lei Fan, Pedro W. Crous, Cheng-Ming Tian.
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.
Citation:
Jiang N, Fan X-L, Crous PW, Tian C-M (2019) Species of Dendrostoma (Erythrogloeaceae, Diaporthales) associated with chestnut and oak canker diseases in China. MycoKeys 48: 67-96. https://doi.org/10.3897/mycokeys.48.31715
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Dendrostoma was recently proposed in Erythrogloeaceae (Diaporthales, Sordariomycetes), with all known members recorded as being plant pathogenic on economically important tree hosts. During our collections of Dendrostoma species in China, mild to severe canker symptoms were observed on sweet chestnut (Castanea mollissima) and oak (Quercus spp.) trees. Dead and dying plant tissues exhibiting Dendrostoma canker symptoms were sampled for fungal isolation. A total of 37 Dendrostoma isolates were obtained and analysed using morphological characteristics and molecular data (ITS, LSU, RPB2, TEF1-α). Based on these data, 10 novel clades could be distinguished, which also proved to represent morphologically distinct species described here as Dendrostoma aurorae, D. castaneae, D. castaneicola, D. chinense, D. dispersum, D. parasiticum, D. qinlingense, D. quercus, D. shaanxiense and D. shandongense spp. nov. A key to species of the genus is also provided.
Canker, Castanea , multi-gene phylogeny, Quercus , systematics
The family Erythrogloeaceae was established to accommodate Chrysocrypta, Disculoides, and Erythrogloeum, which exhibit epiphyllous acervuli along with subcylindrical to ampulliform conidiogenous cells and aseptate conidia (
Dendrostoma (Erythrogloeaceae, Diaporthales) was recently introduced as a phytopathogenic fungal genus causing canker diseases on several economic hardwoods such as Malus spectabilis, Osmanthus fragrans and Quercus acutissima (
The Erythrogloeaceae, including Chrysocrypta, Dendrostoma, Disculoides and Erythrogloeum, represent a family of fungal pathogens occurring on several commercially important tree genera such as Corymbia, Eucalyptus, Hymenaea, Malus, Osmanthus and Quercus in Australia, Brazil, China and Costa Rica (
The aims of present study were (i) to describe the important Dendrostoma spp. associated with canker diseases on chestnut and oak trees in China and (ii) to provide a multi-gene phylogeny for the genus Dendrostoma based on a large set of freshly collected specimens in China. In agreement with previous taxonomic studies in Erythrogloeaceae, where different Disculoides spp. were discovered on Myrtaceae (
Surveys for Dendrostoma species were conducted in plantations, nurseries, parks, gardens, on mountains and natural reserves in Beijing, Hebei, Shaanxi, Shandong, Tianjin and Zhejiang Provinces in China from 2017 to 2018. Typical canker symptoms were observed on stems, branches and twigs of different hosts, including Castanea mollissima, Quercus aliena, Q. aliena var. acuteserrata, Q. wutaishanica and other Quercus species (Fig.
A total of 37 Dendrostoma isolates were established by removing a mucoid spore mass from sporulating ascomata and conidiomata produced on diseased bark, spreading the suspension on the surface of potato dextrose agar (PDA) plates and incubating the plates at 25 °C in the dark for up to 24 h. Single germinating spores were then transferred to clean plates under a dissecting microscope with a sterile needle. Specimens and isolates were deposited in the Museum of Beijing Forestry University (BJFC). Axenic cultures are maintained in the China Forestry Culture Collection Centre (CFCC).
The identification of Dendrostoma spp. was based on morphological features observed on the natural substrates. Cross-sections for ascomata and conidiomata from tree barks were prepared by hand using a double-edged blade under a dissecting microscope. At least 10 conidiomata/ascomata, 10 asci and 50 conidia/ascospores were measured to calculate the mean size and standard deviation. Measurements are reported as maxima and minima in parentheses and the range representing the mean plus and minus the standard deviation of the number of measurements is given in parentheses (
Genomic DNA was extracted from fungal colonies growing on PDA using a modified cetyl trimethyl ammonium bromide method (CTAB;
Sequences generated from the above primers of the different genomic regions (ITS, LSU, TEF1-α and RPB2) were analysed in comparison with those of Dendrostoma mali (CFCC 52102), D. leiphaemia (CBS 187.37), D. osmanthi (CFCC 52106, CFCC 52107, CFCC 52108 and CFCC 52109) and D. quercinum (CFCC 52103, CFCC 52104 and CFCC 52105) from
Isolates and GenBank accession numbers used in the phylogenetic analyses.
Species | Culture | Location | Host | Host family | GenBank accession numbers | |||
---|---|---|---|---|---|---|---|---|
ITS | LSU | TEF1−a | RPB2 | |||||
Chrysocrypta corymbiae | CBS 132528* | Australia | Corymbia sp. | Myrtaceae | JX069867 | JX069851 | MH545457 | MH545415 |
Dendrostoma aurorae | CFCC 52753* | China | Castanea mollissima | Fagaceae | MH542498 | MH542646 | MH545447 | MH545405 |
CFCC 52754 | China | Castanea mollissima | Fagaceae | MH542499 | MH542647 | MH545448 | MH545406 | |
Dendrostoma castaneae | CFCC 52745* | China | Castanea mollissima | Fagaceae | MH542488 | MH542644 | MH545437 | MH545395 |
CFCC 52746 | China | Castanea mollissima | Fagaceae | MH542489 | NA | MH545438 | MH545396 | |
CFCC 52747 | China | Castanea mollissima | Fagaceae | MH542490 | NA | MH545439 | MH545397 | |
CFCC 52748 | China | Castanea mollissima | Fagaceae | MH542491 | NA | MH545440 | MH545398 | |
CFCC 52749 | China | Castanea mollissima | Fagaceae | MH542492 | MH542645 | MH545441 | MH545399 | |
CFCC 52750 | China | Castanea mollissima | Fagaceae | MH542493 | NA | MH545442 | MH545400 | |
CFCC 52751 | China | Castanea mollissima | Fagaceae | MH542494 | NA | MH545443 | MH545401 | |
CFCC 52752 | China | Castanea mollissima | Fagaceae | MH542495 | NA | MH545444 | MH545402 | |
Dendrostoma castaneicola | CFCC 52743* | China | Castanea mollissima | Fagaceae | MH542496 | NA | MH545445 | MH545403 |
CFCC 52744 | China | Castanea mollissima | Fagaceae | MH542497 | NA | MH545446 | MH545404 | |
Dendrostoma chinense | CFCC 52755* | China | Castanea mollissima | Fagaceae | MH542500 | MH542648 | MH545449 | MH545407 |
CFCC 52756 | China | Castanea mollissima | Fagaceae | MH542501 | MH542649 | MH545450 | MH545408 | |
CFCC 52757 | China | Castanea mollissima | Fagaceae | MH542502 | MH542650 | MH545451 | MH545409 | |
CFCC 52758 | China | Castanea mollissima | Fagaceae | MH542503 | MH542651 | MH545452 | MH545410 | |
Dendrostoma dispersum | CFCC 52730* | China | Quercus sp. | Fagaceae | MH542467 | MH542629 | MH545416 | MH545374 |
CFCC 52731 | China | Quercus sp. | Fagaceae | MH542468 | MH542630 | MH545417 | MH545375 | |
Dendrostoma leiphaemia | CBS 187.37 | NA | Quercus sp. | Fagaceae | MH855882 | MH867393 | NA | NA |
Dendrostoma mali | CFCC 52102* | China | Malus spectabilis | Rosaceae | MG682072 | MG682012 | MG682032 | MG682052 |
Dendrostoma osmanthi | CFCC 52106* | China | Osmanthus fragrans | Oleaceae | MG682073 | MG682013 | MG682033 | MG682053 |
CFCC 52108 | China | Osmanthus fragrans | Oleaceae | MG682074 | MG682014 | MG682034 | MG682054 | |
CFCC 52107 | China | Osmanthus fragrans | Oleaceae | MG682075 | MG682015 | MG682035 | MG682055 | |
CFCC 52109 | China | Osmanthus fragrans | Oleaceae | MG682076 | MG682016 | MG682036 | MG682056 | |
Dendrostoma parasiticum | CFCC 52761 | China | Castanea mollissima | Fagaceae | MH542480 | MH542636 | MH545429 | MH545387 |
CFCC 52763 | China | Castanea mollissima | Fagaceae | MH542481 | MH542637 | MH545430 | MH545388 | |
CFCC 52762* | China | Quercus wutaishanica | Fagaceae | MH542482 | MH542638 | MH545431 | MH545389 | |
CFCC 52764 | China | Quercus aliena | Fagaceae | MH542483 | MH542639 | MH545432 | MH545390 | |
CFCC 52765 | China | Castanea mollissima | Fagaceae | MH542484 | MH542640 | MH545433 | MH545391 | |
CFCC 52766 | China | Quercus aliena var. acuteserrata | Fagaceae | MH542485 | MH542641 | MH545434 | MH545392 | |
Dendrostoma qinlingense | CFCC 52732* | China | Quercus wutaishanica | Fagaceae | MH542471 | MH542633 | MH545420 | MH545378 |
CFCC 52733 | China | Quercus aliena var. acuteserrata | Fagaceae | MH542472 | MH542634 | MH545421 | MH545379 | |
Dendrostoma quercinum | CFCC 52103* | China | Quercus acutissima | Fagaceae | MG682077 | MG682017 | MG682037 | MG682057 |
CFCC 52104 | China | Quercus acutissima | Fagaceae | MG682078 | MG682018 | MG682038 | MG682058 | |
CFCC 52105 | China | Quercus acutissima | Fagaceae | MG682079 | MG682019 | MG682039 | MG682059 | |
Dendrostoma quercus | CFCC 52734 | China | Quercus sp. | Fagaceae | MH542473 | NA | MH545422 | MH545380 |
CFCC 52735 | China | Quercus sp. | Fagaceae | MH542474 | NA | MH545423 | MH545381 | |
CFCC 52737 | China | Quercus sp. | Fagaceae | MH542475 | NA | MH545424 | MH545382 | |
CFCC 52739* | China | Quercus sp. | Fagaceae | MH542476 | MH542635 | MH545425 | MH545383 | |
CFCC 52738 | China | Quercus sp. | Fagaceae | MH542477 | NA | MH545426 | MH545384 | |
CFCC 52736 | China | Quercus sp. | Fagaceae | MH542478 | NA | MH545427 | MH545385 | |
CFCC 52740 | China | Quercus sp. | Fagaceae | MH542479 | NA | MH545428 | MH545386 | |
Dendrostoma shaanxiense | CFCC 52741* | China | Castanea mollissima | Fagaceae | MH542486 | MH542642 | MH545435 | MH545393 |
CFCC 52742 | China | Castanea mollissima | Fagaceae | MH542487 | MH542643 | MH545436 | MH545394 | |
Dendrostoma shandongense | CFCC 52759* | China | Castanea mollissima | Fagaceae | MH542504 | MH542652 | MH545453 | MH545411 |
CFCC 52760 | China | Castanea mollissima | Fagaceae | MH542505 | MH542653 | MH545454 | MH545412 | |
Disculoides eucalypti | CBS 132183* | Australia | Eucalyptus sp. | Myrtaceae | JQ685517 | JQ685523 | MH545455 | MH545413 |
Disculoides eucalyptorum | CBS 132184* | Australia | Eucalyptus viminalis | Myrtaceae | JQ685518 | JQ685524 | MH545456 | MH545414 |
A partition homogeneity test with heuristic search and 1000 replicates was performed using PAUP v. 4.0b10 to assess the discrepancy amongst the ITS, LSU, TEF1-α and RPB2 sequence datasets in reconstructing phylogenetic trees. MP analysis was run using a heuristic search option of 1000 search replicates with random-additions of sequences with a tree bisection and reconnection algorithm. Maxtrees were set to 5000, branches of zero length were collapsed and all equally parsimonious trees were saved. Other calculated parsimony scores were tree length (TL), consistency index (CI), retention index (RI) and rescaled consistency (RC). ML analysis was performed using a GTR site substitution model including a gamma-distributed rate heterogeneity and a proportion of invariant sites (
The alignment based on the combined sequence dataset (ITS, LSU, TEF1-α and RPB2) included 46 ingroup taxa and three outgroup taxa, comprising 3536 characters in the aligned matrix. Of these, 2612 characters were constant, 175 variable characters were parsimony-uninformative and 749 characters were parsimony informative (101 from ITS, 21 from LSU, 389 from TEF1-α and 238 from RPB2). The MP analysis resulted in 108 equally most parsimonious trees (TL = 1590, CI = 0.744, RI = 0.897, RC = 0.668); the first tree is shown in Fig.
Dendrostoma mali X.L. Fan & C.M. Tian.
Sexual morph: Pseudostromata small to large, distinct, circular, erumpent, consisting of an inconspicuous ectostromatic disc, semi-immersed to superficial, causing a pustulate bark surface. Ectostromatic disc flat or concave, orange, surrounded by bark flaps. Central column beneath the disc more or less conical. Stromatic zones lacking. Ascomata perithecial, conspicuous, umber to fuscous black, embedded in orange to umber pseudostromatic tissue, regularly scattered, surrounding the ectostromatic disc, with small to long ostioles that emerge within the ectostromatic disc. Ostioles flat in the disc or sometimes slightly projecting, cylindrical, sometimes obscuring the disc, covered by an orange, umber to fuscous black crust. Paraphyses deliquescent. Asci fusoid, 8-spored, 2–3-seriate, with an apical ring, becoming detached from the perithecial wall. Ascospores hyaline, fusoid to cylindrical, symmetrical to asymmetrical, straight to curved, bicellular, with a median septum, constricted at the septum, smooth, multiguttulate. Asexual morph: Conidiomata pycnidial, spherical to conical to pulvinate, occurring separately, immersed to semi-immersed in bark; wall of several layers of yellow textura angularis. Central column beneath the disc conical or not. Conidiophores reduced to conidiogenous cells. Conidiogenous cells lining the inner walls of cavity, hyaline, smooth, subcylindrical to ampulliform. Conidia hyaline, aseptate, smooth, multiguttulate or not, thin-walled, ellipsoid to fusoid, straight to curved.
Dendrostoma aurorae differs from D. chinensis and D. shandongense by the existence of obvious central column.
CHINA. Shaanxi Province: Lan’gao County, chestnut plantation, 32°13'43"N, 109°00'44"E, 1820 m a.s.l., on branches of Castanea mollissima, 3 Jul. 2017, N. Jiang (holotype: BJFC-S1561; ex-type culture: CFCC 52753).
Aurorae, referring to the orange conidiomata with exuding conidial tendrils.
Sexual morph not observed. Asexual morph: Conidiomata pycnidial, conical to pulvinate, occurring separately, bright yellow to orange, semi-immersed in bark, 300–500 μm high, 800–1400 μm diam.; wall of several layers of bright yellow textura angularis; conidiomata exuding slimy orange masses of conidia; central column beneath the disc more or less conical, pale yellow. Conidiophores reduced to conidiogenous cells. Conidiogenous cells lining the inner walls of the cavity, hyaline, smooth, subcylindrical to ampulliform, 4–15 × 2.5–4 μm. Conidia hyaline, aseptate, smooth, multiguttulate, thin-walled, ellipsoid to fusoid, straight to curved, (7.2–)8.1–9.8(–10.3) × (2.1–)2.3–2.6(–2.8) μm, l/w = (2.7–)3.2–4.1(–4.2) (n = 50).
Morphology of Dendrostoma aurorae from Castanea mollissima (BJFC-S1561). A–C Habit of conidiomata on branches D Transverse section of conidioma E Longitudinal section through conidioma F, H Conidia G Conidiogenous cells. Scale bars: 1 mm (A); 0.5 mm (B, C, E); 0.2 mm (D); 5 μm (F, H); 10 μm (G).
On PDA, cultures are initially white, becoming isabelline after 2 weeks. The colonies are flat with irregular edge; texture uniform within 1 month at 25 °C in the dark.
CHINA. Shaanxi Province: Lan’gao County, chestnut plantation, 32°13'43"N, 109°00'44"E, 1820 m a.s.l., on branches of Castanea mollissima, 3 Jul. 2017, N. Jiang, living culture CFCC 52754 (BJFC-S1562).
Dendrostoma aurorae was discovered on stems of dying chestnut trees and appears morphologically similar to the chestnut blight pathogen, Cryphonectria parasitica. However, these two diaporthalean pathogens can be distinguished by the existence of a central column inside the conidiomata of Dendrostoma aurorae. In the genus Dendrostoma, D. aurorae differs from D. chinensis and D. shandongense by the existence of an obvious central column.
Dendrostoma castaneae is distinguished from the phylogenetically closely related species D. castaneicola by its narrower conidia.
CHINA. Hebei Province: Xinglong County, chestnut plantation, 40°21'44"N, 117°51'29"E, 256 m a.s.l., on branches of Castanea mollissima, 27 Apr. 2018, N. Jiang & C.M. Tian (holotype: BJFC-S1553; ex-type culture: CFCC 52745).
Castaneae, referring to the host genus, Castanea.
Sexual morph not observed. Asexual morph: Conidiomata pycnidial, pulvinate, occurring separately, bright yellow to orange, immersed in bark, 400–600 μm high, 900–2200 μm diam.; wall of several layers of brown textura angularis; central column beneath the disc irregular, pale yellow. Conidiophores reduced to conidiogenous cells. Conidiogenous cells lining the inner walls of the cavity, hyaline, smooth, subcylindrical to ampulliform, 3–10 × 2–3.5 μm. Conidia hyaline, aseptate, smooth, multiguttulate, thin-walled, ellipsoid, straight to curved, (9.3–)10.4–12.3(–13.3) × (2.1–)2.2–2.7(–2.9) μm, l/w = (3.4–)4.2–5.2(–5.9) (n = 50).
On PDA, cultures are initially white, exhibiting grey after 2 weeks. Colonies are flat with irregular edge; texture initially uniform, producing concentric circles with faint orange conidiomata distributed outside the rim within 1 month at 25 °C in the dark.
CHINA. Hebei Province: Chengde City, Xinglong County, chestnut plantation, 40°21'44"N, 117°51'29"E, 256 m a.s.l., on branches of Castanea mollissima, 27 Apr. 2018, N. Jiang & C.M. Tian, living culture CFCC 52748 (BJFC-S1556); Hebei Province: Chengde City, Xinglong County, chestnut plantation, 40°21'44"N, 117°51'29"E, 256 m a.s.l., on branches of Castanea mollissima, 27 Apr. 2018, N. Jiang & C.M. Tian, living culture CFCC 52751 (BJFC-S1557); Hebei Province: Chengde City, Xinglong County, chestnut plantation, 40°21'44"N, 117°51'29"E, 256 m a.s.l., on branches of Castanea mollissima, 27 Apr. 2018, N. Jiang & C.M. Tian, living culture CFCC 52747 (BJFC-S1559); Hebei Province: Chengde City, chestnut plantation, 40°37'39"N, 118°27'22"E, 256 m a.s.l., on branches of Castanea mollissima, 28 Apr. 2018, N. Jiang & C.M. Tian, living culture CFCC 52750 (BJFC-S1558); Hebei Province: Chengde City, chestnut plantation, 40°37'39"N, 118°27'22"E, 256 m a.s.l., on branches of Castanea mollissima, 28 Apr. 2018, N. Jiang & C.M. Tian, living culture CFCC 52752 (BJFC-S1560); Tianjin City: Jizhou District, chestnut plantation, 40°06'33"N, 117°42'45"E, 185 m a.s.l., on branches of Castanea mollissima, 25 Apr. 2018, N. Jiang & C.M. Tian, living culture CFCC 52749 (BJFC-S1554); Tianjin City: Jizhou District, chestnut plantation, 40°06'33"N, 117°42'45"E, 185 m a.s.l., on branches of Castanea mollissima, 25 Apr. 2018, N. Jiang & C.M. Tian, living culture CFCC 52746 (BJFC-S1555).
Dendrostoma castaneae is the most common species in this genus occurring on the host Castanea mollissima in China and is associated with canker symptoms on stems and branches. As shown in Fig.
Dendrostoma castaneicola differs from the two phylogenetically closely related species, D. castaneae and D. shaanxiense, by its white central column.
CHINA. Hebei Province: Chengde City, chestnut plantation, 40°24'32"N, 117°28'55"E, 262 m a.s.l., on branches of Castanea mollissima, 28 Apr. 2018, N. Jiang & C.M. Tian (holotype: BJFC-S1551; ex-type culture: CFCC 52743).
Castaneicola, referring to the host genus, Castanea.
Sexual morph not observed. Asexual morph: Conidiomata pycnidial, conical to pulvinate, occurring separately, reddish-orange, semi-immersed in bark, 300–550 μm high, 900–1600 μm diam.; wall of several layers of faint yellow textura angularis; central column beneath the disc more or less conical, white. Conidiophores reduced to conidiogenous cells. Conidiogenous cells lining the inner walls of the cavity, hyaline, smooth, subcylindrical to ampulliform, 5–14 × 2–3.5 μm. Conidia hyaline, aseptate, smooth, multiguttulate, thin-walled, ellipsoid to fusoid, straight, (9.3–)10.5–12.8(–13.8) × (3.1–)3.2–3.8(–4.1) μm, l/w = (2.3–)3–4(–4.4) (n = 50).
On PDA, cultures are initially white, becoming black after 2 weeks. The colonies are flat with irregular edge; texture uniform, producing a circle with faint orange conidiomata distributed along the edge of the circle within 1 month at 25 °C in the dark.
CHINA. Hebei Province: Chengde City, Xinglong County, chestnut plantation, 40°21'44"N, 117°51'29"E, 256 m a.s.l., on branches of Castanea mollissima, 27 Apr. 2018, N. Jiang & C.M. Tian, living culture CFCC 52744 (BJFC-S1552).
Dendrostoma castaneicola, D. castaneae and D. shaanxiense comprise three closely related pathogen species causing chestnut canker diseases in China, all three species occurring on Castanea mollissima. They differ with regard to conidiomatal characteristics, including conidial dimensions (Table
Conidial size of Dendrostoma species from natural host barks, species with * were measured from conidia produced in PDA.
Species | Conidial length (μm) | Conidial width (μm) | Length/width ratio |
Dendrostoma aurorae | 8.1–9.8 | 2.3–2.6 | 3.2–4.1 |
Dendrostoma castaneae | 10.4–12.3 | 2.2–2.7 | 4.2–5.2 |
Dendrostoma castaneicola | 10.5–12.8 | 3.2–3.8 | 3–4 |
Dendrostoma chinense | 7.7–9.1 | 3.4–3.7 | 2.2–2.6 |
Dendrostoma dispersum | 11.1–12.2 | 2–2.3 | 4.9–5.9 |
Dendrostoma mali* | 3.5–4.5 | 2–2.5 | NA |
Dendrostoma osmanthi* | 7.5–10.5 | 2–2.5 | NA |
Dendrostoma parasiticum | 9.3–11.7 | 2.8–3.3 | 3–3.9 |
Dendrostoma qinlingense | 16–18 | 3.3–3.7 | 4.4–5.2 |
Dendrostoma quercinum* | 10.5–14 | 2.5 | NA |
Dendrostoma quercus | 13.3–16.1 | 3.5–4.2 | 3.3–4.4 |
Dendrostoma shaanxiense | 9.5–11.1 | 2.5–3.1 | 3.3–4.2 |
Dendrostoma shandongense | 8.1–8.8 | 3.8–4.3 | 1.9–2.3 |
Dendrostoma chinense differs from D. shandongense by the appearance of conidiomata and is again similar to D. shandongense in its conidial characteristics.
CHINA. Shandong Province: Rizhao City, Donggang District, chestnut plantation, 35°42'28"N, 119°46'23"E, 452 m a.s.l., on branches of Castanea mollissima, 14 Apr. 2017, N. Jiang (holotype: BJFC-S1563; ex-type culture: CFCC 52755).
Chinense, referring to the country, China.
Sexual morph not observed. Asexual morph: Conidiomata pycnidial, spherical, occurring separately, black, semi-immersed in bark, 250–450 μm high, 600–850 μm diam.; wall of several layers of white textura angularis. Conidiophores reduced to conidiogenous cells. Conidiogenous cells lining the inner walls of the cavity, hyaline, smooth, ampulliform, 7–14 × 1–2.5 μm. Conidia hyaline, aseptate, smooth, multiguttulate or not, thin-walled, fusoid to ellipsoid, apex acutely rounded, base truncate, (6.9–)7.7–9.1(–9.7) × (3.3–)3.4–3.7(–3.9) μm, l/w = (1.9–)2.2–2.6(–2.7) (n = 50).
On PDA, cultures are initially white, becoming olive green in the outer zone after 2 weeks. Colonies are flat with a regular edge; texture uniform within 1 month at 25 °C in the dark.
CHINA. Shandong Province: Rizhao City, Donggang District, chestnut plantation, 35°42'28"N, 119°46'23"E, 452 m a.s.l., on branches of Castanea mollissima, 14 Apr. 2017, N. Jiang, living culture CFCC 52756 (BJFC-S1564); Hebei Province: Chengde City, chestnut plantation, 40°24'32"N, 117°28'55"E, 262 m a.s.l., on branches of Castanea mollissima, 29 Apr. 2018, N. Jiang & C.M. Tian, living culture CFCC 52757 (BJFC-S1565); Hebei Province: Chengde City, chestnut plantation, 40°24'32"N, 117°28'55"E, 262 m a.s.l., on branches of Castanea mollissima, 29 Apr. 2018, N. Jiang & C.M. Tian, living culture CFCC 52757 (BJFC-S1566).
Dendrostoma chinense and D. shandongense have been occasionally discovered on the same branches and share similar conidial shape and dimensions. However, the conidiomatal appearance of these two species is quite different (black conidiomata in Dendrostoma chinense vs. orange conidiomata in D. shandongense).
Dendrostoma dispersum can be distinguished from the phylogenetically closely related D. mali and D. quercinum based on its conidial dimensions.
CHINA. Shaanxi Province: Beijing City: Mentougou District, Xiaolongmen Forest Park, 39°55'52"N, 115°45'15"E, 1670 m a.s.l., on branches of Quercus sp., 15 Aug. 2017, N. Jiang & X.L. Fan (holotype: BJFC-S1537; ex-type culture: CFCC 52730).
Dispersum, referring to the conidiomata scattered on the bark surface.
Sexual morph not observed. Asexual morph: Conidiomata pycnidial, conical to spherical, occurring separately, bright yellow, semi-immersed in bark, 500–800 μm high, 900–1500 μm diam.; wall of several layers of bright yellow textura angularis; central column beneath the disc conical, bright yellow. Conidiophores reduced to conidiogenous cells. Conidiogenous cells lining the inner walls of the cavity, hyaline, smooth, subcylindrical to ampulliform, 6–15 × 2.5–5 μm. Conidia hyaline, aseptate, smooth, multiguttulate, thin-walled, ellipsoid to fusoid, straight to curved, (10.9–)11.1–12.2(–12.8) × (1.9–)2–2.3(–2.4) μm, l/w = (4.8–)4.9–5.9(–6.3) (n = 50).
On PDA, cultures are initially white, becoming faint yellow after 2 weeks. The colonies are flat with regular edge; texture uniform, producing concentric circles within 1 month at 25 °C in the dark.
CHINA. Beijing City: Yanqing District, Yudu Mountain, 40°53'48"N, 115°54'48"E, 840 m a.s.l., on branches of Quercus sp., 12 Mar. 2018, N. Jiang, X.L. Fan, Y.M. Liang & C.M. Tian, living culture CFCC 52731 (BJFC-S1538).
Dendrostoma dispersum is phylogenetically close to D. mali and D. quercinum (Fig.
Dendrostoma parasiticum is distinguished from D. quercus by its shorter and narrower conidia.
CHINA. Shaanxi Province: Shangluo City, Zhashui County, Longtougou Village, 33°39'27"N, 109°07'15"E, 2504 m a.s.l., on branches of Quercus wutaishanica, 8 Jul. 2017, N. Jiang (holotype: BJFC-S1570; ex-type culture: CFCC 52762).
Parasiticum, referring to the fungus causing canker diseases on different hosts.
Sexual morph not observed. Asexual morph: Conidiomata pycnidial, conical to spherical, occurring separately, yellow, semi-immersed in bark, 350–600 μm high, 1000–1800 μm diam.; wall of several layers of bright yellow textura angularis; central column beneath the disc conical, bright yellow. Conidiophores reduced to conidiogenous cells. Conidiogenous cells lining the inner walls of the cavity, hyaline, smooth, subcylindrical to ampulliform, 7–12 × 2–3.5 μm. Conidia hyaline, aseptate, smooth, multiguttulate, thin-walled, fusoid, straight, (9.2–)9.3–11.7(–13.6) × (2.7–)2.8–3.3(–3.6) μm, l/w = (2.7–)3–3.9(–4.2) (n = 50).
On PDA, cultures are initially white, becoming dark orange after 2 weeks. The colonies are flat with irregular edge; texture uniform, producing concentric circles within 1 month at 25 °C in the dark.
CHINA. Shaanxi Province: Shangluo City, Zhashui County, chestnut plantation, 33°39'27"N, 109°07'15"E, 2504 m a.s.l., on branches of Castanea mollissima, 8 Jul. 2017, N. Jiang, living culture CFCC 52762 (BJFC-S1569); Shaanxi Province: Ankang City, Xiangxidong Park, 32°40'32"N, 109°18'57"E, 2504 m a.s.l., on branches of Castanea mollissima, 29 Jun. 2017, N. Jiang, living culture CFCC 52763 (BJFC-S1571); Beijing City: Mentougou District, Xiaolongmen Forest Park, 39°17'25"N, 115°45'23"E, 452 m a.s.l., on branches of Castanea mollissima, 17 Aug. 2017, N. Jiang & X.L. Fan, living culture CFCC 52764 (BJFC-S1572); Beijing City: Yanqing District, Yudu Mountain, 40°53'48"N, 115°54'48"E, 840 m a.s.l., on branches of Quercus aliena, 12 Mar. 2017, N. Jiang, X.L. Fan, Y.M. Liang & C.M. Tian, living culture CFCC 52765 (BJFC-S1573); Hebei Province: Chengde City, chestnut plantation, 40°24'32"N, 117°28'55"E, 262 m a.s.l., on branches of Quercus aliena var. acutiserrata, 15 Oct. 2017, N. Jiang, living culture CFCC 52766 (BJFC-S1574).
Dendrostoma parasiticum constitutes a widely distributed species occurring on several Fagaceae tree species including Castanea mollissima, Quercus aliena, Q. aliena var. acuteserrata and Q. wutaishansea. Dendrostoma parasiticum appears to be associated with tree dieback, canker and even tree death, although its pathogenicity remains unproven. Dendrostoma parasiticum is close to D. quercus in the phylogram (Fig.
Dendrostoma qinlingense produces the largest conidia amongst known species of the genus.
CHINA. Baoji City, Mei County, Taibai Mountain, 34°15'43"N, 107°88'42"E, 2752 m a.s.l., on branches of Quercus wutaishanica, 13 Jul. 2017, N. Jiang (holotype: BJFC-S1539; ex-type culture: CFCC 52732).
Qinlingense, referring to the Qinling Mountain.
Sexual morph not observed. Asexual morph: Conidiomata pycnidial, conical to pulvinate, occurring separately, dark yellow, semi-immersed in bark, 400–700 μm high, 1100–1600 μm diam.; wall of several layers of bright yellow textura angularis; central column beneath the disc conical, dark orange. Conidiophores reduced to conidiogenous cells. Conidiogenous cells lining the inner walls of the cavity, hyaline, smooth, ampulliform, 6–22 × 2–3.5 μm. Conidia hyaline, aseptate, smooth, multiguttulate, thin-walled, fusoid, straight, (15.6–)16–18(–18.6) × (3.1–)3.3–3.7(–3.8) μm, l/w = (4.2–)4.4–5.2(–5.8) (n = 50).
On PDA, cultures are initially white, exhibiting light grey after 2 weeks. The colonies are flat with irregular edge; texture uniform, producing concentric circles with sparse conidiomata irregularly distributed on the centre of the plate within 1 month at 25 °C in the dark.
CHINA. Shaanxi Province: Baoji City, Mei County, Taibai Mountain, 34°15'43"N, 107°88'42"E, 2752 m a.s.l., on branches of Quercus aliena var. acutiserrata, 13 Jul. 2017, N. Jiang, living culture CFCC 52733 (BJFC-S1540).
Dendrostoma qinlingense was discovered on two Quercus species on the Qinling Mountain in northwest China. This species is phylogenetically related to Dendrostoma osmanthi on Osmanthus fragrans. However, Dendrostoma qinlingense differs from D. osmanthi by much larger conidia (16–18 × 3.3–3.7 μm in D. qinlingense vs. 7.5–10 × 2–2.5 μm in D. osmanthi).
Dendrostoma quercus is recognised by the existence of dimorphic conidia, which is unique in the genus.
CHINA. Hebei Province: Qinhuangdao City, Zu Mountain, 40°14'13"N, 119°43'28"E, 1125 m a.s.l., on branches of Quercus sp., 2 May 2018, N. Jiang & C.M. Tian (holotype: BJFC-S1547; ex-type culture: CFCC 52739).
Quercus, referring to the host genus, Quercus.
Sexual morph: Pseudostromata erumpent, consisting of an inconspicuous ectostromatic disc, semi-immersed to superficial, causing a pustulate bark surface, 1000–1500 µm diam. Ectostromatic disc flat or concave, pale brown to brown, sometimes concealed by ostioles, surrounded by bark flaps, 400–800 µm diam.; central column yellowish to brownish. Stromatic zones lacking. Perithecia conspicuous, umber to fuscous black, 350–500 µm diam. Ostioles 5–8 per disc, flat in the disc or sometimes slightly projecting, cylindrical, covered by an orange, umber to fuscous black crust, 60–80 µm diam. Paraphyses slightly deliquescent. Asci fusoid to slightly fusiform, 8-spored, ascospores regularly disposed, with an apical ring, 55–65 × 8–11 µm. Ascospores hyaline, fusoid to cylindrical, smooth, often containing one guttule per cell to multiguttulate, symmetrical to asymmetrical, straight curved, bicellular, (13.4–)13.8–15.6(–16.6) × (5.1–)5.3–5.8(–5.9) μm, l/w = (2.4–)2.5–2.8(–2.9) (n = 50). Asexual morph: Conidiomata pycnidial, conical, occurring separately, pale yellow, semi-immersed in bark, 700–1000 μm high, 700–950 μm diam.; wall of several layers of pale yellow textura angularis; central column beneath the disc conical, yellow. Conidiophores reduced to conidiogenous cells. Conidiogenous cells lining the inner walls of the cavity, hyaline, smooth, subcylindrical to ampulliform, 4.5–9 × 2–4 μm. Conidia hyaline, aseptate, smooth, multiguttulate, thin-walled, dimorphic, type one (> 99%) ellipsoid to fusoid, straight to curved, (11–)13.3–16.1(–16.9) × (3.4–)3.5–4.2(–4.5) μm, l/w = (2.6–)3.3–4.4(–4.9) (n = 50); type two (< 1%) fusoid, apex acutely rounded, 13–16 × 4–6 μm.
Morphology of Dendrostoma quercus from Quercus sp. (BJFC-S1547). A–C Habit of psedostromata on branches D Transverse section of pseudostroma E, H Habit of conidiomata on branches F Transverse section of conidioma G Longitudinal section through conidioma I Conidiogenous cells producing dimorphic conidia J Secondary conidia K Asci and ascospores L Ascospores M Primary conidia. Scale bars: 1 mm (A, H); 0.5 mm (B–G); 10 μm (I, K–M); 5 μm (J).
On PDA, cultures are initially white, becoming dark grey after 2 weeks. The colonies are flat with irregular edge; texture uniform, producing concentric circles with sparse conidiomata irregularly distributed within 1 month at 25 °C in the dark.
CHINA. Hebei Province: Qinhuangdao City, Zu Mountain, 40°14'13"N, 119°43'28"E, 1125 m a.s.l., on branches of Quercus sp., 2 May 2018, N. Jiang & C.M. Tian, living culture CFCC 52734 (BJFC-S1548); Hebei Province: Qinhuangdao City, Zu Mountain, 40°14'13"N, 119°43'28"E, 1125 m a.s.l., on branches of Quercus sp., 2 May 2018, N. Jiang & C.M. Tian, living culture CFCC 52735 (BJFC-S1541); Hebei Province: Qinhuangdao City, Zu Mountain, 40°14'13"N, 119°43'28"E, 1125 m a.s.l., on branches of Quercus sp., 2 May 2018, N. Jiang & C.M. Tian, living culture CFCC 52736 (BJFC-S1542); Hebei Province: Qinhuangdao City, Zu Mountain, 40°14'13"N, 119°43'28"E, 1125 m a.s.l., on branches of Quercus sp., 2 May 2018, N. Jiang & C.M. Tian, living culture CFCC 52737 (BJFC-S1543); Hebei Province: Qinhuangdao City, Zu Mountain, 40°14'13"N, 119°43'28"E, 1125 m a.s.l., on branches of Quercus sp., 2 May 2018, N. Jiang & C.M. Tian, living culture CFCC 52738 (BJFC-S1544); Hebei Province: Qinhuangdao City, Zu Mountain, 40°14'13"N, 119°43'28"E, 1125 m a.s.l., on branches of Quercus sp., 2 May 2018, N. Jiang & C.M. Tian, living culture CFCC 52740 (BJFC-S1545).
Dendrostoma quercus is associated with oak branch cankers and forms both sexual and asexual fruiting structures beneath cankered bark. Within the genus, D. quercus produces the second largest conidia, smaller only than those of D. qinlingense (Table
Dendrostoma shaanxiense is distinguished from the closely related species D. castaneae by smaller l/w ratio and from D. castaneicola by its narrower conidia.
CHINA. Shaanxi Province: Ankang City, Xiangxidong Park, 32°40'32"N, 109°18'57"E, 1079 m a.s.l., on branches of Castanea mollissima, 1 Jul. 2017, N. Jiang (holotype: BJFC-S1549; ex-type culture: CFCC 52741).
Shaanxiense, referring to the Shaanxi Province in China.
Sexual morph not observed. Asexual morph: Conidiomata pycnidial, conical to pulvinate, occurring separately, dark orange, semi-immersed in bark, 350–650 μm high, 1050–1400 μm diam.; wall of several layers of bright yellow textura angularis; central column beneath the disc conical, bright yellow. Conidiophores reduced to conidiogenous cells. Conidiogenous cells lining the inner walls of the cavity, hyaline, smooth, subcylindrical to ampulliform, 5–11 × 2.5–3.5 μm. Conidia hyaline, aseptate, smooth, multiguttulate, thin-walled, ellipsoid to fusoid, straight to curved, (8.6–)9.5–11.1(–11.7) × (2.3–)2.5–3.1(–3.4) μm, l/w = (2.8–)3.3–4.2(–4.9) (n = 50).
On PDA, cultures are initially white, turning purple after 2 weeks on PDA. The colonies are flat with irregular edge; texture uniform, producing concentric circles within 1 month at 25 °C in the dark.
Shaanxi Province: Ankang City, Xiangxidong Park, 32°40'32"N, 109°18'57"E, 1079 m a.s.l., on branches of Castanea mollissima, 1 Jul. 2017, N. Jiang, CFCC 52742 (BJFC-S1550).
Dendrostoma shaanxiense, D. castaneae and D. castaneicola are phylogenetically closely related species occurring on the same host, Castanea mollissima (Fig.
Dendrostoma shandongense is distinguished from its closest relative D. chinensis by the colour of conidiomata.
CHINA. Shandong Province: Rizhao City, Donggang District, chestnut plantation, 35°42'28"N, 119°46'23"E, 452 m a.s.l., on branches of Castanea mollissima, 14 Apr. 2017, N. Jiang (holotype: BJFC-S1567; ex-type culture: CFCC 52759).
Shandongense, referring to the Shandong Province in China.
Sexual morph not observed. Asexual morph: Conidiomata pycnidial, spherical, occurring separately, reddish-orange, semi-immersed in bark, 250–400 μm high, 450–650 μm diam.; wall of several layers of black textura angularis. Conidiophores reduced to conidiogenous cells. Conidiogenous cells lining the inner walls of cavity, hyaline, smooth, ampulliform, 6.5–13 × 1–2.5 μm. Conidia hyaline, aseptate, smooth, multiguttulate, thin-walled, fusoid to ellipsoid, apex acutely rounded, base truncate, (7.8–)8.1–8.8(–9) × (3.7–)3.8–4.3(–4.8) μm, l/w = (1.6–)1.9–2.3(–2.4) (n = 50).
On PDA, cultures are white. The colonies are flat with irregular edge; texture uniform, producing sparse conidiomata irregularly distributed near the centre of the plate within 1 month at 25 °C in the dark.
Shandong Province: Rizhao City, Donggang District, chestnut plantation, 35°42'28"N, 119°46'23"E, 452 m a.s.l., on branches of Castanea mollissima, 14 Apr. 2017, N. Jiang, CFCC 52760 (BJFC-S1568).
Dendrostoma shandongense and D. chinensis occasionally occur on the same branches. These species are best distinguished by the appearance of their conidiomata, which are black in Dendrostoma chinense and orange in D. shandongense.
In this study, we reviewed the taxonomic circumscription of Dendrostoma using molecular and morphological data. This is the first study that presents a robust phylogeny using a number of Dendrostoma isolates from different geographic origins. The results revealed up to 14 species in Dendrostoma based on the observation of type specimens and ex-type cultures (D. leiphaemia was not observed), of which 10 species were shown to represent new species, namely D. aurorae, D. castaneae, D. castaneicola, D. chinense, D. dispersum, D. parasiticum, D. qinlingense, D. quercus, D. shaanxiense and D. shandongense.
The 13 type specimens in Dendrostoma (except D. leiphaemia) were examined to establish robust morphological characteristics amongst specific ranks. Amongst these, 3 species, Dendrostoma mali, D. osmanthi and D. quercinum, were discovered to only have a sexual morph on natural hosts; 9 species, D. aurorae, D. castaneae, D. castaneicola, D. chinense, D. dispersum, D. parasiticum, D. qinlingense, D. shaanxiense and D. shandongense, were observed with only an asexual morph and only one species, D. quercus, was represented by both asexual and sexual morphs. Hence, morphological differences amongst Dendrostoma species were mainly established based on conidiomata produced on diseased host tissues, including colours of conidiomata, culture characteristics (Fig. 13), existence or non-existence of a central column, conidial shape and dimensions.
Dendrostoma shandongense and D. chinense are similar in conidial shape and size, but differ markedly from the other species. Additionally, Dendrostoma shandongense and D. chinense comprise the only two species in the genus with conidiomata lacking a central column structure, although they differ considerably with regard to in conidiomatal appearance (Figs
1 | Asexual morphs with or without sexual morphs known from natural substrates | 2 |
– | Only sexual morph known from natural substrates | 11 |
2 | Central column absent, length/width ratio of conidia < 3 | 3 |
– | Central column present, length/width ratio of conidia > 3 | 4 |
3 | Conidiomata orange | D. shandongense |
– | Conidiomata black | D. chinense |
4 | Conidia dimorphic | D. quercus |
– | Conidia monomorphic | 5 |
5 | Conidial length > 15 μm | D. qinlingense |
– | Conidial length < 15 μm | 6 |
6 | Conidial length/width ratio > 4.2 | 7 |
– | Conidial length/width ratio < 4.2 | 8 |
7 | Conidial length/width ratio 4.2–5.2, conidial width 2.2–2.7 μm | D. castaneae |
– | Conidial length/width ratio 4.9–5.9, conidial width 2–2.3 μm | D. dispersum |
8 | Central column white | D. castaneicola |
– | Central column bright yellow or pale yellow | 9 |
9 | Central column pale yellow | D. aurorae |
– | Central column bright yellow | 10 |
10 | Conidial width 2.8–3.3 μm, length/width ratio 3–3.9 | D. parasiticum |
– | Conidial width 2.5–3.1 μm, length/width ratio 3.3–4.2 | D. shaanxiense |
11 | Ascospores width > 5 μm | D. leiphaemia |
– | Ascospores width < 5 μm | 12 |
12 | Ascospores length > 15 μm | D. quercinum |
– | Ascospores length < 15 μm | 13 |
13 | On Osmanthus, Ascospores 11.5–14.5 × 3.5–4 μm | D. osmanthi |
– | On Malus, Ascospores 12–14 × 3–4 μm | D. mali |
The genus Dendrostoma was initially proposed to include three presumed plant pathogens causing canker diseases on hardwood trees, namely D. mali on Malus spectabilis, D. osmanthi on Osmanthus fragrans and D. quercinum on Quercus acutissima (
The tree genera Castanea and Quercus in Fagaceae contain numerous important and common tree species in China, including C. mollissima, C. crenata, C. henryi, C. seguinii, Q. acutissima, Q. aliena, Q. dentata, Q. mongolica and Q. wutaishanica (Flora of China website: http://frps.eflora.cn/). Castanea mollissima constitutes one the most important crop tree species widely cultivated in 26 provinces in China. However, many plantations and nurseries planting Chinese chestnut suffer from fungal diseases that cause high production losses (
In the present study, seven Dendrostoma species were observed on the host Castanea mollissima including D. aurorae, D. castaneae, D. castaneicola, D. chinense, D. parasiticum, D. shaanxiense and D. shandongense, causing chestnut canker diseases, termed Dendrostoma canker herein. Dendrostoma canker constitutes a newly discovered disease that has been observed in chestnut plantations and nurseries. Species of Dendrostoma usually infect host branches and stems, with occasional infection of twigs. Maturation of the fruiting structures from June to July resulted in death of the infected branches. Notably, no sexual fruiting structures were discovered during our investigations on chestnut trees.
Accurate recognition and identification of plant diseases are essential as fungal pathogens are constantly evolving and traditional control methods are frequently insufficient for disease control. In comparison, in the present study, Dendrostoma canker is considered to be caused by up to eight different species of Dendrostoma. Further studies are, however, required to confirm their pathogenicity and fully resolve their ecology.
This study was financed by the National Natural Science Foundation of China (Project No.: 31670647). We thank Yingmei Liang [Museum of Beijing Forestry University (BJFC), Beijing Forestry University], Chungen Piao and Minwei Guo [China Forestry Culture Collection Center (CFCC), Chinese Academy of Forestry, Beijing] for the preservation of materials studied during this study.