Research Article |
Corresponding author: Yong Li ( lylx@caf.ac.cn ) Academic editor: Rungtiwa Phookamsak
© 2022 Cheng-Bin Wang, Ning Jiang, Han Xue, Chun-Gen Piao, Yong Li.
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:
Wang C-B, Jiang N, Xue H, Piao C-G, Li Y (2022) Colletotrichum chinense sp. nov. from Yucca gloriosa and C. quercicola sp. nov. from Quercus variabilis in China. MycoKeys 93: 1-21. https://doi.org/10.3897/mycokeys.93.89209
|
Colletotrichum is an important plant pathogenic genus causing anthracnose on a wide range of host plants. During 2019 and 2021, Colletotrichum isolates were obtained during surveys of anthracnose on garden plants in China. Multi-gene phylogenetic analyses of internal transcribed spacer (ITS), glyceraldehyde-3-phosphate dehydrogenase (gapdh), chitin synthase 1 (chs-1), actin (act) and beta-tubulin (tub2) sequences coupled with morphological evidence support the introduction of two novel species namely Colletotrichum chinense sp. nov. from Yucca gloriosa in Beijing and C. quercicola sp. nov. from Quercus variabilis in Shaanxi Province. Phylogenetic inference revealed that two isolates of C. chinense belonged to the agaves species complex and were closely related to C. agaves, and differed from the other species within this species complex by shorter conidia and the host association. Molecular identification showed that two isolates of C. quercicola formed a highly supported lineage close to C. tanaceti in the destructivum species complex, which could be distinguished from C. tanaceti by straighter conidia. In pathogenicity tests, yellow spots and orange conidial masses displayed on the inoculated Y. gloriosa leaves and brown spots appeared on the inoculated Q. variabilis leaves. In addition, C. chinense and C. quercicola were re-isolated from spots of the tested leaves of Y. gloriosa and Q. variabilis.
Ascomycota, multigene phylogeny, new species, taxonomy
The genus Colletotrichum (Glomerellaceae, Glomerellales, Sordariomycetes) is represented by its type species Colletotrichum lineola (
Previously, species of Colletotrichum were distinguished based on host range and a suite of morphological characteristics, especially the size and shape of conidia, appressoria, and sporulating structures (
To establish a stable and natural classification system,
Many species of Colletotrichum have been identified as plant pathogens causing anthracnose on a wide range of hosts, especially in subtropical and tropical regions, leading to significant economic losses (
In the present study, by using a nucleotide basic local alignment search tool (BLASTn) analysis (
Recently, we investigated the phylogenetic diversity of Colletotrichum species associated with anthracnose on garden plants in China. Four novel isolates were collected from Y. gloriosa and Q. variabilis in Beijing and Shaanxi, respectively. The aim of this study was to identify these isolates based on phylogenetic data and morphology and to confirm their pathogenicity.
From 2019 to 2021, symptomatic leaves of garden plants were collected in China. Specimens were transferred to the laboratory in paper bags and stored at 4 °C until further processing. The surface of diseased leaves were sterilized with 70% ethanol and 2% NaClO for 1 min, rinsed three times with sterile water, and then samples were cut into 0.4 × 0.4 cm small pieces excised from the margins of foliar lesions, and placed on potato dextrose agar (PDA; potato extract 20 g, dextrose 20 g, agar 20 g, 1 L distilled water) plates at 25 °C in the dark. After 2–3 days, single colonies growing from the diseased tissue were transferred to new PDA plates. Single-spore cultures were obtained from the pure colonies and examined morphologically. The cultures were deposited in the China Forestry Culture Collection Center (CFCC; http://cfcc.caf.ac.cn/), and the specimens in the herbarium of the Chinese Academy of Forestry (CAF; http://museum.caf.ac.cn/).
Agar plugs (6 mm in diameter) were taken from the edge of actively growing cultures on PDA and transferred in triplicate on PDA, synthetic low-nutrient agar (SNA;
Total genomic DNA was extracted from fungal mycelia using a CTAB DNA extraction protocol (
Newly generated sequences from the four isolates in this study were assembled using SeqMan v. 7.1.0, and the closest match using BLASTn analyses. Reference Colletotrichum sequences (Table
Phylogenetic analyses using Maximum Likelihood (ML) and Bayesian Inference (BI) were performed. ML analyses were constructed on the RAxML-HPC BlackBox 8.2.10 (
The pathogenicity of two Colletotrichum isolates was assessed on detached healthy Y. gloriosa and Q. variabilis plants in the greenhouse. Leaves were washed in running distilled water, surface-sterilized in 70% ethanol and 2% NaClO for 1 min, then rinsed in sterile distilled water. Spores were harvested from two-week-old PDA plates with 10 ml of sterilized water with spore suspension filtered through two layers of cheesecloth to eliminate debris and mycelium. The conidial suspension was adjusted to a final inoculum concentration of 1 × 106–107 conidia/mL with sterile deionized water. Then 10 µL of conidial suspension was placed in the middle portion of the leaves, and inoculated sterile water in the additional leaves served as control. Each treatment had three replicates (three leaves), and the experiment was carried out twice. The inoculated leaves were placed in transparent plastic bags at 25 °C and over 90% humidity in the dark for 14 days. After appearance of symptoms, fungus isolates were re-isolated from the infected leaves and identified based on the morphological and phylogenetic analyses to fulfill Koch’s postulates.
Closest matches in BLASTn searches with the ITS sequences, these isolates were preliminarily identified to be in the agaves and destructivum species complexes. Further, phylogenetic trees were constructed based on combined loci of ITS, gapdh, act, chs-1 and tub2 sequences to identify these isolates to species level.
For the agaves species complex, DNA sequences of five genes were obtained from two isolates from Y. gloriosa in this study, with seven reference strains of the agaves species complex, and C. boninense (CBS 123755, ex-type) and C. brasiliense (CBS 128501, ex-type) as the outgroup taxa. A total of 1649 characters including alignment gaps (578 for ITS, 94 for gapdh, 232 for chs-1, 240 for act and 505 for tub2) were included in the phylogenetic analyses. Of these characters, 1271 were constant, 162 were variable and parsimony-uninformative, and 216 were parsimony-informative. The resulting ML and BI trees had similar topologies; the ML tree (Fig.
Phylogenetic tree obtained by Maximum likelihood analyses using the combined ITS, gapdh, chs-1, act and tub2 sequence alignments of the agaves species complex. Numbers above the branches indicate ML bootstraps (left, MLBS ≥ 50%) and Bayesian Posterior Probabilities (right, BPP ≥ 0.7). The tree is rooted with C. boninense (CBS 123755, ex-type) and C. brasiliense (CBS 128501, ex-type).
For the destructivum species complex, DNA sequences of five genes were obtained from two isolates from Q. variabilis in this study, and 44 reference strains of the destructivum species complex, and C. truncatum (IMI 135524) and C. fusiforme (MFLUCC 12-0437) as the outgroup taxa. A total of 1875 characters including gaps (560 for ITS, 236 for gapdh, 280 for chs-1, 274 for act and 525 for tub2) were obtained in the phylogenetic analyses. Of these characters, 1292 were constant, 177 were variable and parsimony-uninformative, and 406 were parsimony-informative. The resulting ML and BI trees had similar topologies; the ML tree (Fig.
Phylogenetic tree obtained by Maximum likelihood analyses using the combined ITS, gapdh, chs-1, act and tub2 sequence alignments of the destructivum species complex. Numbers above the branches indicate ML bootstraps (left, MLBS ≥ 50%) and Bayesian Posterior Probabilities (right, BPP ≥ 0.7). The tree is rooted with C. fusiforme (
Referring to the country, where the species was first collected.
Sexual morph not observed. Asexual morph developed on PDA. Setae and chlamydospores not observed. Conidiomata acervular, abundant, pulvinate, 200–500 μm diam. Conidiophores smooth-walled, unbranched, septate, sometimes constricted at the septa, hyaline, up to 40 µm long. Conidiogenous cells 6.5–19.5 × 3–8 µm (x– = 12.7 ± 2.7 × 5.3 ± 1.3 µm, n = 20), subglobose to ampulliform, smooth-walled, hyaline. Conidia 9.5–25.5 × 3.5–8.5 µm (x– = 14.8 ± 1.8 × 6 ± 1 μm, n = 50), L/W ratio = 2–2.7, cylindrical, obtuse at the apex, smooth-walled, hyaline, contents granular. Appressoria not observed.
Colonies on PDA, flat, with an entire margin, with sparse aerial mycelium, covered with orange conidial masses, reaching 23–25 mm diam in 7 days at 25 °C. Colonies on MEA, flat, with no aerial mycelium, covered with slimy conidial masses, reaching 15–20 diam in 7 days at 25 °C. Colonies on SNA flat, sparse white hyphae, with an entire margin, reaching 12–15 diam in 7 days at 25 °C.
China, Beijing City, isolated from leaf spot of Yucca gloriosa L., Cheng-Bin Wang, 15 August 2020 (holotype CAF800056; ex-type living culture: CFCC 57501); Ibid (living culture: CFCC 57502).
Colletotrichum beeveri of the boninense species complex and C. tofieldiae of the spaethianum species complex have been reported from Yucca before the present study (
Species | Type | Media for Conidia morph | Hosts | Distribution | Conidia (µm) | Appressoria (µm) | Reference |
---|---|---|---|---|---|---|---|
C. agaves | Epitype | PDA | Agave spp. | Mexico; USA; Netherlands | (17.5–)19.0–30.5(–33) × 5–8(–9.5) on | Not observed |
|
C. chinense | Holotype | PDA | Yucca gloriosa | China | (9.5–)12.5–16.5(–25.5) × (3.5–)6.0–7.0(–8.5) | Not observed | This study |
C. euphorbiae | Holotype | SNA | Euphorbia sp | South Africa | (17–)23–28(–28.5) × (6–)6.5–7 | (6.5–)8.5–14.5(–20.5) × (5.5–)6–10.5(–16) |
|
C. ledebouriae | Holotype | PNA | Ledebouria floribunda | South Africa | (15–)17–21(–22) × (5–)6 | Not observed | Crous et al. (2016) |
C. neosansevieriae | Holotype | SNA | Sansevieria trifasciata | South Africa | (16–)18–22(–25) × (4–)5–6 | Not observed |
|
C. sansevieriae | Holotype | PDA | Sansevieria spp. | Asia; Australia; USA | 12.5–(18.4)–32.5 × 3.8–(6.4)–8.8 PDA | 6.3–(7.7)–8.8 × 6.3–(7.3)–7.5 |
|
Referring to the host genus, Quercus.
Sexual morph not observed. Asexual morph developed on PDA. Chlamydospores not observed. Conidiomata acervular, abundant, globose to pulvinate, 200–400 μm diam. Conidiophores, hyaline, branched, smooth-walled, up to 50 μm long. Setae medium brown, smooth-walled, 60–145 μm long, 1–3-septate. Conidiogenous cells 6–18 × 3–7 µm (x– = 7.9 ± 3.6 × 4 ± 1.2 µm, n = 20), hyaline, smooth-walled, cylindrical to elongate ampulliform. Conidia 14.5–23 × 3–5 µm (x– = 17 ± 1.7 × 3.9 ± 0.5 μm, n = 50), L/W ratio =4–5, hyaline, smooth-walled, fusiform, straight to slightly curved with both ends rounded or one end round and the other truncate. Appressoria 6–11 × 4–8 µm (x– = 8.4 ± 1.4× 5 ± 1 μm, n = 50), L/W ratio = 1.5–2, single, medium brown, smooth-walled, subglobose, ovate to broadly elliptical in outline.
Colonies on PDA flat, with moderate aerial mycelium, margin white to light gray, gray to brown in the center, reaching 46–50 mm diam in 7 days at 25 °C. Colonies on MEA flat, covered by white aerial mycelium, white margin and light orange in the center, reaching 30–35 mm diam after 7 days at 25 °C. Colonies on SNA flat, with entire margin, covered by sparse white aerial mycelium, reaching 20 mm diam after 7 days at 25 °C.
China, Shaanxi Province, Foping County, Dongshan Park, isolated from leaf spot of Quercus variabilis Bl., Yong Li, 11 September 2019 (holotype CAF800057; ex-type living culture: CFCC 54457); Ibid (living culture: CFCC 57507).
Four Colletotrichum species are presently known to occur on Quercus hosts, viz. C. clidemiae, C. gloeosporioides, C. karstii and C. theobromicola (
Pathogenicity tests were conducted to confirm Koch’s postulates on Q. variabilis leaves for C. quercicola, and on Y. gloriosa leaves for C. chinense. After 14 days of inoculation, necrotic lesions and typical orange conidial masses were observed from the inoculated site of Y. gloriosa leaves, and Q. variabilis leaves showed brown spot from the inoculated site, whereas all control leaves remained healthy (Fig.
Typical field symptoms of disease and artificial inoculation results A–E Yucca gloriosa leaves F–J Quercus variabilis leaves A, F Anthracnose field symptoms B–D Symptoms resulting from Colletotrichum chinense (CFCC 57501; ex-type) after 14 days G–I symptoms resulting from Colletotrichum quercicola (CFCC 54457; ex-type) after 14 days E, J symptoms resulting from sterile deionized water after 14 days.
In the present study, we collected garden plants with anthracnose symptoms or leaf spots in China. From these samples, the obtained Colletotrichum isolates were identified based on morphological features of the asexual morph obtained in culture and five combined loci (ITS, gapdh, chs-1, act and tub2) phylogenies. The phylogenetic analyses revealed two novel species, C. chinense from Y. gloriosa in Beijing, and C. quercicola from Q. variabilis in the Shaanxi Province, and morphological characters can distinguish these isolates from related species. Pathogenicity test revealed C. chinense appearing as a causal agent of Y. gloriosa anthracnose and C. quercicola as a pathogen of Q. variabilis anthracnose.
ITS is evaluated as a universal DNA barcode marker for fungi (
The agaves species complex groups Colletotrichum agaves, and four related species, C. ledebouriae, C. neosansevieriae, C. euphorbiae and C. sansevieriae (
Species in the destructivum species complex are serious pathogens undergoing a hemibiotrophic lifestyle and have been associated with 49 plant species belonging to 41 genera (
Morphological comparison of species in the destructivum species complex.
Species | Type | Media for Conidia morph | Hosts | Distribution | Conidia (µm) | Appressoria (µm) | Reference |
---|---|---|---|---|---|---|---|
C. americae-borealis | Holotype | SNA | Medicago sativa; Glycyrrhiza uralensis | America; China | (13.5–)15.5–18(–19) × 3.5–4 | (4.5–)6–10.5(–13) × (3.5–)4–7(–10) |
|
C. antirrhinicola | Holotype | SNA | Antirrhinum majus | New Zealand; Japan | (14.5–)15.5–19(–23.5) × (3.5–) 4–4.5(–5) | (9–)9.5–12(–13.5) × (5–)6–8(–10) |
|
C. atractylodicola | Holotype | PDA | Atractylodes lancea | China | 13.5–19 × 4–6.5 | 7.5–14 × 7–10.5 |
|
C. bryoniicola | Holotype | SNA | genera of Asteraceae, Convolvulaceae, and Fabaceae; etc | Netherlands; Italy | (13.5–)15–18.5(–22) × 4–5(–5.5) | (3.5–) 4–10(–18) × (2.5–)3.5–6.5(–7.5) |
|
C. destructivum | Epitype | SNA | Trifolium spp.; Bletilla ochracea; Phragmites sp.; etc | worldwide | (14–)14.5–16.5(–18) × 3.5–4(–4.5) | (6.5–)10–15.5(–20.5) × (4.5–)5–8(–10.5 |
|
C. fuscum | Epitype | SNA | Digitalis spp.; Heracleum sp.; Coreopsis lanceolata | Germany; Italy; Netherlands | (16–)16.5–20(–34) × (3.5–)4–4.5(–5.5) | (6–)8.5–14.5(–19) × (6.5–)7–10(–11.5) |
|
C. higginsianum | Epitype | SNA | Brassicaceae; Campanula sp.; Rumex acetosa | Italy; Japan, Korea; Trinidad; Tobago; America | (17–)19–20.5(–21) × (3–)3.5–4(–4.5) | (5.5–)10–20(–28.5) × (3.5–) 5–9(–12) |
|
C. lentis | Holotype | SNA | Lens culinaris; Vicia sativa | Canada; China; Romania | (13–)16–20(–26) × 3–4(–5) | (5–)5.5–7.5(–9) × (3.5–)4.5–6(–6.5) |
|
C. lini | Epitype | SNA | Linum sp.; Nigella sp.; Taraxacum sp.; etc | France; Germany; America; Ireland; Tunisia;Netherlands | (13–)15–18(–22.5) × (3–)3.5–4(–4.5) | (5–)6.5–10(–12.5) × (4–)4.5–6(–7) |
|
C. neorubicola | Holotype | PDA | Rubus idaeus | China | (14.8–)21.5–22.7(–23.5) × (4–)4.9–5.1(–5.6) | (4–)8.2–10.5(–17.5)× (3.6–)5.6–6.8(–11.7) |
|
C. ocimi | Holotype | SNA | Ocimum basilicum | Italy; Australia | 14.5–15.5(–16.5) × (3.5–)4–4.5 | (6.5–)7–13(–15.5) × (4–)4.5–7.5(–9) |
|
C. quercicola | Holotype | PDA | Quercus variabilis | China | (14–)14.5–17.5(–21.5) × (3–)3.3–4.3(–4.7) | (5.7–)6.8–9.7(–10) × (3.2–)4–6(–8) | This study |
C. panacicola | Panax sp. | Eastern Asia | 17.0–22.1 × 3.4–5.1 | 14–8 |
|
||
C. pleopeltidis | Holotype | SNA | Pleopeltis sp. | South Africa | (15–)19–23(–25) × (5–)5.5(–6) | Not described |
|
C. pisicola | Holotype | SNA | Pisum sp. | America | (11–)15–21(–29.5) × (3–)3.5–4 | (5.5–)7–11.5(–13.5) × (4–)4.5–6(–6.5) |
|
C. shisoi | Holotype | PDA | Perilla frutescens | Japan | (15.0–)17–19(–27.0) × (3.0–)4.0(–5.0) | (7.0–)9.0–10.0(–11.0) × (5.0–)7.0–8.0 |
|
C. tabacum | Neotype | SNA | Nicotiana spp., Centella asiatica | France; India; Germany; Madagascar; Zimbabwe | (11·5–) 19–20 (–27) × (3–) 5·5–5·8 (–7·6) | (10–) 11·5–12·5 (–14·5) × (6·5–) 8·5–9·5 (–11·5) |
|
C. tanaceti | Holotype | SNA | Tanacetum cinerariifolium | Australia | (13–)14.5–17.5(–19) × (3–)3.5–4(–4.5) | (5–)6.5–12(–14.6)× (3.5–)4.5–7(–10) |
|
C. utrechtense | Holotype | PDA | Trifolium pratense | Netherlands | 17.5–20.5(–23) × 3.5–4(–4.5) | (7–)10–14.5(–15) × (5–)6.5–9.5(–10) |
|
C. vignae | Holotype | SNA | Vigna unguiculata | Nigeria | (12–)14–17.5(–18.5) × (3–)3.5–4(–4.5) | (4–)4.5–8.5(–12.4)× (3.5–)4–5(–6.5) |
|
Although morphological characters may not prove taxonomically informative for species differentiation within species complex, they are considered as a basis to taxonomic segregation for distinguishing species between different species complexes (
This research was funded by the National Microbial Resource Center of the Ministry of Science and Technology of the People’s Republic of China (NMRC-2021-7).