Research Article |
Corresponding author: Yu-Cheng Dai ( yuchengdai@bjfu.edu.cn ) Corresponding author: Bao-Kai Cui ( cuibaokai@yahoo.com ) Academic editor: Maria-Alice Neves
© 2018 Jie Song, Yi-Fei Sun, Xing Ji, Yu-Cheng Dai, Bao-Kai Cui.
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:
Song J, Sun Y-F, Ji X, Dai Y-C, Cui B-K (2018) Phylogeny and taxonomy of Laetiporus (Basidiomycota, Polyporales) with descriptions of two new species from western China. MycoKeys 37: 57-71. https://doi.org/10.3897/mycokeys.37.26016
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Laetiporus is a cosmopolitan genus of brown rot fungi. In this study, L. medogensis and L. xinjiangensis are described as new species from western China, based on morphological and molecular evidence. L. medogensis has only been found on gymnosperms so far and is distinguished by pinkish-buff to clay-buff pileal surface and buff-yellow pore surface, azonate to faintly zonate pileus and ellipsoid to ovoid basidiospores (5–6.2 × 4.2–5.2 μm). L. xinjiangensis is found on angiosperms and is characterised by pale-buff to clay-pink pileal surface, cream to light yellow pore surface, azonate to faintly zonate pileus, large pores (2–3 per mm) and small basidiospores (4.5–5 × 3–4.2 μm). The phylogeny of Laetiporus is reconstructed with multi-gene sequences including the internal transcribed spacer regions (ITS), the large subunit (nrLSU) and small subunit (nrSSU) of the nuclear ribosomal RNA gene, the small subunit of the mitochondrial rRNA gene (mtSSU), the translation elongation factor 1-α gene (EF-1α) and the second subunit of RNA polymerase II (RPB2). The results show that L. medogensis and L. xinjiangensis formed two distinct lineages belonging to Laetiporus. Illustrated descriptions of the two new species are presented. An identification key to species of L. sulphureus complex is provided.
Brown-rot fungi, multi-gene phylogeny, Fomitopsidaceae , taxonomy, wood-decaying fungi
Laetiporus Murrill (Fomitopsidaceae, Polyporales) is a cosmopolitan genus, causing brown rot on living hardwoods and conifers (
A molecular phylogenetic study of Laetiporus in Japan identified three species, viz. L. cremeiporus, L. montanus and L. versisporus (
In the present study, the two new Laetiporus species from western China (Clade P and Clade Q) are described based on morphological and phylogenetic analyses.
Morphological studies followed
Genomic DNA was extracted from dried fruiting bodies using a cetyltrimethylammonium bromide rapid plant genome extraction kit (Aidlab Biotechnologies Co., Ltd., Beijing) according to the manufacturer’s instructions with some modifications (
A list of species, specimens and GenBank accession numbers of sequences used in this study.
Species | Collection no. | GenBank Accessions | |||||
---|---|---|---|---|---|---|---|
ITS | nrLSU | nuSSU | mtSSU | EF-1α | RPB2 | ||
Antrodia serialis | Cui 10519 | KP715307 | KP715323 | KR605911 | KR606011 | KP715337 | KR610830 |
Fomitopsis pinicola | Cui 10405 | KC844852 | KC844857 | KR605857 | KR605961 | KR610690 | KR610781 |
Laetiporus ailaoshanensis | Dai 13567 (Paratype) | KX354470 a | KX354498 a | KX354535 a | KX354577 a | KX354623 a | KX354665 a |
L. ailaoshanensis | Dai 13256 (Holotype) | KF951289 a | KF951317 a | KX354537 a | KX354579 a | KX354625 a | KT894786 a |
L. caribensis | PR 6583 | JN684766 | - | - | - | - | - |
L. caribensis | PR 914 | JN684762 | EU402526 | - | EU402482 | - | - |
L. caribensis | PR 6521 | JN684771 | - | - | - | - | - |
L. cincinnatus | Dai 12811 | KF951291 a | KF951304 a | KX354516 a | KX354558 a | KX354605 a | KT894788 a |
L. cincinnatus | DA 37 | EU402557 | EU402521 | - | EU402485 | AB472661 | - |
L. cincinnatus | JV 0709/168J | KF951290 a | KF951305 a | KX354517 a | KX354559 a | KX354606 a | KX354651 a |
L. conifericola | JV 0709/81J | KF951292 a | KF951327 a | KX354531 a | KX354573 a | KX354683 a | |
L. conifericola | CA 8 | EU402575 | EU402523 | - | EU402487 | AB472663 | - |
L. conifericola | JAM 1 | EU402577 | EU402524 | - | EU402486 | AB472664 | - |
L. cremeiporus | Dai 10107 | KF951281 a | KF951301 a | KX354515 a | KX354557 a | KX354604 a | KX354650 a |
L. cremeiporus | Cui 10991 | KF951279 a | KF951298 a | - | KX354595 a | KX354641 a | KX354679 a |
L. cremeiporus | Cui 10586 | KF951277 a | KF951297 a | KX354513 a | KX354555 a | KX354602 a | KX354648 a |
L. gilbertsonii | JV 1109/31 | KF951293 a | KF951306 a | KX354542 a | KX354584 a | KX354630 a | KX354671 a |
L. gilbertsonii | TJV 2000/101 | EU402553 | EU402528 | - | EU402493 | AB472668 | - |
L. gilbertsonii | CA 13 | EU402549 | EU402527 | - | EU402496 | AB472666 | - |
L. huroniensis | HMC 3 | EU402571 | EU402540 | - | - | - | - |
L. huroniensis | MI 14 | EU402573 | EU402539 | - | EU402489 | AB472672 | - |
L. medogensis | Cui 12219 (Paratype) | KX354472 a | KX354500 a | KX354538 a | KX354580 a | KX354626 a | KX354667 a |
L. medogensis | Cui 12240 (Holotype) | KX354473 a | KX354501 a | KX354539 a | KX354581 a | KX354627 a | KX354668 a |
L. medogensis | Cui 12390 (Paratype) | KX354474 a | KX354502 a | KX354540 a | KX354582 a | KX354628 a | KX354669 a |
L. montanus | Dai 15888 | KX354466 a | KX354494 a | KX354530 a | KX354572 a | KX354619 a | KX354662 a |
L. montanus | Cui 10011 | KF951274 a | KF951315 a | KX354528 a | KX354570 a | KX354617 a | KT894790 a |
L. montanus | Cui 10015 | KF951273 a | KF951311 a | KX354529 a | KX354571 a | KX354618 a | KT894791 a |
L. sp. 1 | EUC 1 | EU402545 | EU402541 | - | - | - | - |
L. sp. 1 | KOA 1 | EU402546 | EU402542 | - | - | - | - |
L. sp. 2 | RV4A | EU840662 | - | - | - | - | - |
L. sp. 2 | RV5A | EU840663 | - | - | - | - | - |
L. sp. 3 | Munez 207 | JN684764 | - | - | - | - | - |
L. sp. 4 | Robledo 1122 | JN684765 | - | - | - | - | - |
L. sulphureus | Cui 12389 | KR187106 a | KX354487 a | KX354519 a | KX354561 a | KX354608 a | KX354653 a |
L. sulphureus | Cui 12388 | KR187105 a | KX354486 a | KX354518 a | KX354560 a | KX354607 a | KX354652 a |
L. sulphureus | Dai 12154 | KF951295 a | KF951302 a | KX354521 a | KX354563 a | KX354610 a | KX354655 a |
L. sulphureus | Z.R.L. CA04 | KX354479 a | KX354506 a | KX354545 a | KX354587 a | KX354633 a | KX354674 a |
L. sulphureus | Z.R.L. CA08 | KX354480 a | KX354507 a | KX354546 a | KX354588 a | KX354634 a | KX354675 a |
L. sulphureus | DA 41 | EU40256 | EU402533 | - | EU402481 | AB472660 | - |
L. sulphureus | TJV 99/150 | EU402567 | EU402530 | - | EU402492 | - | - |
L. sulphureus | MAS 2 | EU402568 | EU402531 | - | EU402491 | - | - |
L. sulphureus | JV 1106/15 | KF951296 a | KF951303 a | KX354520 a | KX354562 a | KX354609 a | KX354654 a |
L. versisporus | Cui 7882 | KF951269 a | KF951323 a | - | KX354596 a | KX354642 a | KT894783 a |
L. versisporus | Li 15071314 | KX354476 a | KX357139 a | - | KX354598 a | KX354644 a | KX354680 a |
L. versisporus | Dai 13160 | KF951266 a | KF951320 a | - | KX354597 a | KX354643 a | KT894785 a |
L. versisporus | Yuan 6319 | KX354475 a | KX354503 a | KX354541 a | KX354583 a | KX354629 a | KX354670 a |
L. versisporus | Dai 10992 | KF951272 a | KF951325 a | - | KX354600 a | KX354646 a | KX354681 a |
L. versisporus | Dai 13052 | KF951271 a | KF951324 a | - | KX354601 a | KX354647 a | KX354682 a |
L. xinjiangensis | Dai 15825 (Paratype) | KX354465 a | KX354493 a | KX354527 a | KX354569 a | KX354616 a | KX354661 a |
L. xinjiangensis | Dai 15828 (Paratype) | KX354461 a | KX354489 a | KX354523 a | KX354565 a | KX354612 a | KX354657 a |
L. xinjiangensis | Dai 15953 (Holotype) | KX354460 a | KX354488 a | KX354522 a | KX354564 a | KX354611 a | KX354656 a |
L. xinjiangensis | Dai 15898A (Paratype) | KX354464 a | KX354492 a | KX354526 a | KX354568 a | KX354615 a | KX354660 a |
L. zonatus | HKAS 71806 (Paratype) | KF951284 a | KF951310 a | KX354548 a | KX354590 a | KX354636 a | KT894796 a |
L. zonatus | Cui 10403 (Paratype) | KF951282 a | KF951307 a | KX354550 a | KX354592 a | KX354638 a | - |
L. zonatus | Cui 10404 (Holotype) | KF951283 a | KF951308 a | KX354551 a | KX354593 a | KX354639 a | KT894797 a |
Bayesian Inference (BI), Maximum Likelihood (ML) and Maximum Parsimony (MP) analyses were applied to the combined dataset. The best fit model of nucleotide evolution to each individual genetic marker and the combined dataset was selected with AIC (Akaike Information Criterion) using MrModeltest 2.3 (
ML searches were conducted with RAxML-HPC2 on Abe through the Cipres Science Gateway (www.phylo.org) and comprised 100 ML searches under the GTRGAMMA model, with all model parameters estimated by the programme. Only the maximum likelihood best tree from all searches was kept. In addition, 100 rapid bootstrap replicates were run with the GTRCAT model to assess the reliability of the nodes.
MP analysis was applied to the combined dataset as in
Branches that received bootstrap support for maximum parsimony (MP), maximum likelihood (ML) and Bayesian posterior probabilities (BPP) greater than or equal to 75% (MP/ML) and 0.95 (BPP) were considered as significantly supported.
The combined dataset (ITS+nrLSU+nrSSU+mtSSU+EF-1α+RPB2) included sequences from 55 samples representing 19 taxa. Antrodia serialis and Fomitopsis pinicola were used as outgroups. The dataset had a total aligned length of 3963 characters, of which 3137 (79.2%) were constant, 301 (7.6%) were variable and parsimony uninformative and 525 (13.2%) were parsimony informative. The parsimony analysis yielded 68 equally parsimonious trees (TL = 1173, CI = 0.812, RI = 0.865, RC = 0.702, HI = 0.188). The multiple sequence alignment and tree files were deposited at TreeBase (submission ID 21249; www.treebase.org). MP analysis and BI resulted in similar topologies as the ML analysis. The consensus tree inferred from the ML analysis with MP, ML and BPP values is shown in Figure
Samples of Laetiporus clustered together with significant support (100% MP, 100% ML and 1.00 BPP; Figure
Strict consensus tree illustrating the phylogeny of Laetiporus generated by ML analysis based on ITS+nrLSU+nrSSU+mtSSU+EF-1α+RPB2 sequences. Branch support is indicated where MP/BS support is greater than 50% and collapsed below that support threshold. BPP is indicated when greater than 0.95. New species are indicated in bold.
Differs from other Laetiporus species by its pinkish-buff to clay-buff pileal surface, buff-yellow pore surface and ellipsoid to ovoid basidiospores (5–6.2 × 4.2–5.2 μm).
Medogensis (Lat.): referring to the locality (Medog County) of the type specimens.
CHINA. Xizang Auto. Reg. (Tibet), Medog County, on living tree of Abies, 21 Sep 2014, Cui 12240 (BJFC 017154).
Annual, sessile to laterally substipitate, imbricate, fleshy when fresh, crumbly when dry, without odour or taste. Pileus flabelliform to dimidiate, applanate, projecting up to 9 cm, 12 cm wide and 1 cm thick. Pileal surface pinkish-buff to clay-buff when fresh, becoming pale yellow upon drying, glabrous, azonate to faintly zonate. Margin soft and slightly viscous, fawn when juvenile, fading to reddish-brown when dry. Pore surface buff-yellow when fresh, becoming pale yellow to cream when dry; sterile margin cream when fresh, up to 3 mm wide; pores angular, 2–4 per mm; dissepiments thin, entire to lacerate. Context white when fresh, becoming cream to pale yellow when dry, up to 8.5 mm thick. Tubes concolorous with pore surface, crumbly or chalky, up to 1.5 mm long.
Hyphal system dimitic; generative hyphae simple-septate; skeletal hyphae IKI–, CB–, dissolving in KOH. Generative hyphae in context infrequent, hyaline, thin-walled, occasionally branched, up to 11 µm in diam.; skeletal hyphae in context dominant, thick-walled with a wide lumen, frequently branched and interwoven, occasionally simple-septate, hyaline, 4–11 μm in diam. Generative hyphae in tubes dominant, hyaline, thin-walled, frequently branched, simple-septate, 4–5 µm in diam.; skeletal hyphae in tubes thick-walled with a wide lumen, occasionally branched and simple-septate, subparallel along the tubes, 3–5 µm in diam.
Cystidia and other sterile hyphal elements absent.
Basidia clavate, 20–25 × 8–9 μm, bearing four sterigmata and a basal simple-septum; basidioles clavate, smaller than basidia.
Basidiospores ellipsoid to ovoid, hyaline, thin-walled, smooth, IKI–, CB–, 5–6.2 × 4.2–5.2 μm, L = 5.78 μm, W = 4.73 μm, Q = 1.22–1.23 (n = 60/2).
(paratypes) examined. CHINA. Xizang Auto. Reg. (Tibet), Medog County, on living tree of Abies, 20 Sep 2014, Cui 12218 (BJFC 017132) & Cui 12219 (BJFC 017133); 21 Sep 2014, Cui 12241 (BJFC 017155); 24 Aug 2014, Cui 12390 (BJFC 017304).
Differs from other Laetiporus species by its pale-buff to clay-pink pileal surface, cream to light-yellow pore surface, large pores (2–3 per mm) and smaller basidiospores (4.5–5 × 3–4.2 μm).
Xinjiangensis (Lat.): referring to the locality (Xinjiang Autonomous Region) of the type specimens.
CHINA. Xinjiang Auto. Reg., Ili Kazak Autonomous Prefecture, Gongliu County, West Tianshan National Nature Reserve, on living tree of Betula, 14 Sep 2015, Dai 15953 (BJFC 020054).
Annual, sessile to laterally substipitate, imbricate, odour distinctive, taste with acid flavor, fleshy when fresh, crumbly when dry. Pilei flabelliform to dimidiate, applanate, projecting up to 15 cm, 20 cm wide and 3 cm thick. Pileal surface pale-buff to clay-pink when fresh, becoming pale-buff to cream upon drying, glabrous, azonate to faintly zonate when fresh. Margin blunt, clay-buff to greyish-brown to brown when juvenile, fading to dark brown when dry. Pore surface cream to light yellow when fresh, becoming pale yellow when dry; sterile margin pale yellow when fresh, up to 2 mm wide; pores angular, 2–3 per mm; dissepiments thin, entire to lacerate. Context white when fresh, becoming cream to pale yellow when dry, up to 2.2 cm thick. Tubes concolorous with pore surface, crumbly or chalky, up to 8 mm long.
Hyphal system dimitic; generative hyphae simple-septate; skeletal hyphae IKI–, CB–, dissolving in KOH. Generative hyphae in context infrequent, hyaline, thin-walled, occasionally branched, up to 11 µm in diam.; skeletal hyphae in context dominant, hyaline, thick-walled with a wide lumen, frequently branched and interwoven, occasionally simple-septate, 8–15 μm in diam. Generative hyphae in tubes dominant, hyaline, thin-walled, frequently branched, simple-septate, 4–6 µm in diam.; skeletal hyphae in tubes thick-walled with a wide lumen, occasionally branched and simple-septate, subparallel along the tubes or interwoven, 3–5 µm in diam.
Cystidia and other sterile hyphal elements absent.
Basidia clavate, 20–25 × 6–8 μm, bearing four sterigmata and a basal simple-septum; basidioles clavate, smaller than basidia.
Spores. Basidiospores ellipsoid to ovoid, hyaline, thin-walled, smooth, IKI–, CB–, 4.5–5 × 3–4.2 μm, L = 4.87 μm, W = 3.65 μm, Q = 1.33–1.37 (n = 60/2).
(paratypes) examined. CHINA. Xinjiang Auto. Reg., Shihezi, on living tree of Populus, 9 Sep 2015, Dai 15825 (BJFC 019930) & Dai 15828 (BJFC 019931); Burqin County, on living tree of Salix, 9 Sep 2015, Dai 15836 (BJFC 019937) & Dai 15838 (BJFC 019939); Burqin County, Kanas Integrated Nature Landscape Protect Region, on living tree of Salix, 11 Sep 2015, Dai 15893 (BJFC019994); Ili Kazak Autonomous Prefecture, on living tree of Populus, 13 Sep 2015, Dai 15902 (BJFC 020003) & Dai 15905 (BJFC 020006); 4 Oct 2015, Dai 15898A (BJFC 019999).
Recent studies indicated that Laetiporus sulphureus in East Asia is a species complex, comprising several morphologically and ecologically distinct species (
Laetiporus medogensis and L. ailaoshanensis group together with moderate to low MP and ML support (50% MP and 53% ML). Both L. medogensis and L. ailaoshanensis are found in Southwest China. Morphologically, L. ailaoshanensis is similar to L. medogensis by producing orange to yellow pileal surface, white context and ellipsoid to ovoid basidiospores. However, L. medogensis is found on conifers and the pore surface is yellow; L. ailaoshanensis grows on hardwoods and has a white pore surface (
Laetiporus xinjiangensis, L. sulphureus and L. montanus are all common in Northwest China. Both L. xinjiangensis and L. sulphureus grow on angiosperms and group together in the phylogenetic tree with moderate MP, ML and significant BI support (65% MP, 51% ML and 0.98 BPP). Morphologically, L. sulphureus is similar to L. xinjiangensis in having yellowish pore surface and ovoid to ellipsoid basidiospores; however, L. sulphureus produces larger basidiospores (5–7 × 4–5 μm) and has smaller pores (2–5 per mm;
Our research expanded the number of Laetiporus species to 17 around the world. However, studies in the Southern Hemisphere are still few and the relationships amongst Laetiporus species remain unresolved (
1 | Pore surface light goldenrod to sulphur yellow or light yellow when fresh | 2 |
– | Pore surface cream to white when fresh | 10 |
2 | Occurring on conifers | 3 |
– | Occurring on hardwoods | 6 |
3 | Distributed in cool temperate to boreal zones in East Asia and Europe | 4 |
– | Distributed in North America | 5 |
4 | Basidiospores 6–8 × 4–5.5 µm | L. montanus |
– | Basidiospores 5–6.2 × 4.2–5.2 μm | L. medogensis |
5 | Basidiospores 5–7 × 3.8–5 µm; distributed in eastern North America | L. huroniensis |
– | Basidiospores 6.5–8 × 4–5 µm; distributed in far western North America | L. conifericola |
6 | Pores 4–5 per mm | L. caribensis |
– | Pores 2–4 per mm | 7 |
7 | Basidiocarps single, occasionally imbricate but not in large clusters; anamorphic form frequently produced | L. versisporus |
– | Basidiocarps imbricate, rarely single; no anamorphic form or rarely produced | 8 |
8 | Basidiospores 4.5–5 × 3–4.2 µm | L. xinjiangensis |
– | Basidiospores 5–7 × 3–5.5 µm | 9 |
9 | Distributed in temperate zones | L. sulphureus |
– | Distributed in temperate to tropical zones | L. gilbertsonii |
10 | Basidiocarps arising from soil or surface of roots near the base of living trees | L. cincinnatus |
– | Basidiocarp arising from trunks of standing trees or on fallen logs | 11 |
11 | Distributed in mountain forests of subtropical zones | L. ailaoshanensis |
– | Distributed in cool temperate to boreal zones | 12 |
12 | Pileal surface cream to white, pores 3–6 per mm | L. zonatus |
– | Pileal surface light orange to reddish-orange, pores 2–4 per mm | L. cremeiporus |
The main morphological characters, host trees and distribution areas of species in the Laetiporus sulphureus complex.
Species | Pileal surface | Pore surface | Pores | Basidiospores | Distribution | Host | References |
---|---|---|---|---|---|---|---|
L. ailaoshanensis | orange yellow to reddish orange | cream to buff | 3–5/mm | ovoid to ellipsoid 5.0–6.2 × 4.0–5.0 µm |
subtropical areas of south-western China | Lithocarpus |
|
L. caribensis | orange to pale orange | lemon yellow | 4–5/mm | ellipsoid 4.0–4.5 × 2.7–3.6 µm |
tropical zones of the Caribbean basin and central America | Guarea guidonia, Dacryodes |
|
L. cincinnatus | bright salmon orange | pale cream | 2–4/mm | broadly ovoid 4.5–5.5 × 3.5–4.0 µm |
throughout the eastern USA except for in the states along the Gulf of Mexico, common in the Great Lakes regions | arising from the soil (Quercus) |
|
L. conifericola | bright orange to salmon orange | lemon yellow to bright creamy yellow | 2–4/mm | broadly ovoid 6.5–8.0 × 4.0–5.0 µm |
western North America from California to Alaska | Tsuga, Picea, Abies, Pinus |
|
L. cremeiporus | light orange to reddish-orange | yellowish-white to cream | 2–4/mm | ovoid to ellipsoid 5.6–7.0 × 3.9–4.7 µm |
cool temperate to boreal areas of East Asia | Quercus, Pyrus, Prunus |
|
L. gilbertsonii | pale salmon orange or pale pinkish-orange | lemon yellow to pale lemon yellow (in West USA) or isabelline to nearly white (in Southeast USA) | 2–4/mm | broadly ovoid 5.0–6.5 × 3.5–4.5 µm |
North America, Central and South America | Eucalyptus, Quercus, Prunus |
|
L. huroniensis | bright orange | lemon yellow | 2–4/mm | broadly ovoid 5.0–7.0 × 4.2–5.0 µm |
eastern North America and in its Great Lakes areas | Tsuga |
|
L. medogensis | pinkish-buff to clay-buff | buff-yellow | 2–4/mm | ellipsoid to ovoid 5–6.2 × 4.2–5.2 μm |
cool temperate areas of south-western China | Abies | in the present study |
L. montanus | light orange to reddish-orange | bright sulphurous yellow | 1–4/mm | pyriform or ovoid to ellipsoid 6.0–8.0 × 4.0–5.5 µm |
boreal zones in north-eastern China and in mountain areas of Japan and Central Europe | Picea, Larix, Abies |
|
L. sulphureus | bright salmon orange | lemon yellow | 2–4/mm | ovoid to ellipsoid 5.0–6.8 × 4.0–5.0 µm |
North America, Europe and South America | Acer, Salix, Gleditisa, Quercus, Fraxinus, Castanea, Salix |
|
L. versisporus | whitish to sulphur yellow | usually yellow, sometimes pale yellow to nearly white | 3–6/mm | ovoid to short ellipsoid 4.0–6.8 × 3.0–5.5 µm |
cool temperate to tropical areas of East Asia | Robinia, Castanea, Quercus, Elaeocarpus, Castanopsis |
|
L. xinjiangensis | pale-buff to clay-pink | cream to light yellow | 2–3/mm | ellipsoid to ovoid 4.5–5 × 3–4.2 μm |
temperate areas of western China | Betula, Populus, Salix | in the present study |
L. zonatus | white to cream and buff to clay-buff at base | white to cream | 2–5/mm | ellipsoid to pyriform or drop-shaped 5.8–7.2 × 4.3–5.5 µm |
high mountains of temperate areas of south-western China | Quercus |
|
Special thanks are due to Dr. Xiao-Lan He (Soil and Fertilizer Research Institute, Sichuan Academy of Agricultural Sciences, China) and Dr. Xiao-Yong Liu (Institute of Microbiology of the Chinese Academy of Sciences, China) for help in collecting specimens. The research is supported by the Fundamental Research Funds for the Central Universities (No. 2016ZCQ04) and the National Natural Science Foundation of China (Project Nos. 31750001, 31670016).