Abstract
In 2007 a new Stemphylium leaf spot disease of Beta vulgaris (sugar beet) spread through the Netherlands. Attempts to identify this destructive Stemphylium sp. in sugar beet led to a phylogenetic revision of the genus. The name Stemphylium has been recommended for use over that of its sexual morph, Pleospora, which is polyphyletic. Stemphylium forms a well-defined monophyletic genus in the Pleosporaceae, Pleosporales (Dothideomycetes), but lacks an up-to-date phylogeny. To address this issue, the internal transcribed spacer 1 and 2 and intervening 5.8S nr DNA (ITS) of all available Stemphylium and Pleospora isolates from the CBS culture collection of the Westerdijk Institute (N = 418), and from 23 freshly collected isolates obtained from sugar beet and related hosts, were sequenced to construct an overview phylogeny (N = 350). Based on their phylogenetic informativeness, parts of the protein-coding genes calmodulin and glyceraldehyde-3-phosphate dehydrogenase were also sequenced for a subset of isolates (N = 149). This resulted in a multi-gene phylogeny of the genus Stemphylium containing 28 species-clades, of which five were found to represent new species. The majority of the sugar beet isolates, including isolates from the Netherlands, Germany and the UK, clustered together in a species clade for which the name S. beticola was recently proposed. Morphological studies were performed to describe the new species. Twenty-two names were reduced to synonymy, and two new combinations proposed. Three epitypes, one lectotype and two neotypes were also designated in order to create a uniform taxonomy for Stemphylium.
Key words: Morphology, Multi-gene phylogeny, Pleospora
Taxonomic novelties: New combinations: Stemphylium armeriae (Corda) Woudenb. & Crous, S. halophilum (J. Webster) Woudenb. & Crous
New species: S. canadense Woudenb. & Crous, S. chrysanthemicola Woudenb. & Crous, S. lucomagnoense Woudenb. & Crous, S. novae-zelandiae Woudenb. & Crous, S. simmonsii Woudenb. & Crous
Typification (Basionyms): Epitypifications: Alternaria lancipes Ellis & Everh., Stemphylium solani G.F. Weber, Thyrospora astragali Yoshii
Lectotypification: Thyrospora astragali Yoshii
Neotypifications: Pleospora pomorum A.S. Horne, Thyrospora lycopersici Enjoji
Introduction
In 2007 a new leaf spot disease associated with a Stemphylium sp. was first discovered on sugar beet (Beta vulgaris) in the Netherlands, which subsequently spread rapidly throughout the country in the following years (Hanse 2013). The causal agent was recently formally named as Stemphylium beticola (Crous et al. 2016), but the genus itself was not treated in that study.
Stemphylium is a dematiaceous hyphomycete, which can be distinguished from other hyphomycetes forming phaeodictyospores based on the percurrent rejuvenation of its conidiophores, and apically swollen conidiogenous cells. Other closely related genera mostly display a geniculate, sympodial proliferation, e.g. Alternaria (Simmons 2007). Stemphylium, with S. botryosum as type species, forms a well-defined monophyletic genus in the family Pleosporaceae, Pleosporales (Câmara et al., 2002, Inderbitzin et al., 2009). However, the sexual morph to which Stemphylium is linked, Pleospora, is known to be polyphyletic. The type species of Pleospora, Pleospora herbarum, has Stemphylium herbarum as asexual morph (Simmons 1985), but several Pleospora spp. have been linked to a range of different asexual genera (e.g. Inderbitzin et al., 2006, De Gruyter et al., 2013, Ariyawansa et al., 2015, Crous and Groenewald, 2017). The latest comprehensive phylogenetic study on Pleospora species with Stemphylium asexual morphs was published in 2009 (Inderbitzin et al. 2009), which left many unnamed and potentially new Stemphylium species. The Pleospora herbarum clade sensu Inderbitzin et al. (2009) illustrated the problems with identification in the genus. Based on a multi-gene phylogeny five species should be synonymised, but RAPD fingerprints (Chaisrisook et al. 1995), morphology and ecology studies supported them to be separate species. Some researchers therefore chose to retain all the species names (e.g. Inderbitzin et al. 2009), while others again chose to synonymise them (e.g. Köhl et al. 2009). With the uptake of the one fungus-one name initiative in the International Code of Nomenclature for algae, fungi and plants (ICN, McNeill et al., 2012), name changes in these genera became necessary. The use of Stemphylium over Pleospora has subsequently been recommended by the Working Group on Dothideomycetes of the International Committee on the Taxonomy of Fungi (Rossman et al. 2015).
The aim of the present study was to construct a phylogenetic overview of the genus Stemphylium. All available Stemphylium and Pleospora isolates from the CBS collection, together with Stemphylium isolates collected from sugar beet from different parts of the Netherlands as well as from the UK and Germany, were included in the study. The internal transcribed spacer 1 and 2 and intervening 5.8S nr DNA (ITS) were sequenced to construct a draft overview phylogeny. Using a reduced set of isolates, the phylogenetic informativeness of six commonly used protein-coding genes, namely partial actin (actA), beta-tubulin (tub2), calmodulin (cmdA), translation elongation factor 1-alpha (tef1), glyceraldehyde-3-phosphate dehydrogenase (gapdh) and DNA-directed RNA polymerase second largest subunit (rpb2) were also evaluated. Based on these results, the two most promising genes were additionally sequenced for the genus Stemphylium, and used to construct a multi-gene phylogeny.
Materials and methods
Isolates
Four-hundred-and-forty-one isolates were included in this study, comprising of 418 Pleospora and Stemphylium isolates from the culture collection of the Westerdijk Fungal Biodiversity Institute (CBS), Utrecht, the Netherlands (Supplementary Table 1) and 23 isolates received from the IRS (the research and knowledge centre for sugar beet cultivation in The Netherlands), Bergen op Zoom, the Netherlands (Supplementary Table 2). The dataset includes 48 (ex-)type strains. Freeze-dried strains from the CBS culture collection were revived in 2 mL malt/peptone (50 %/50 %) and subsequently transferred to oatmeal agar (OA) (Crous et al. 2009). Strains stored in liquid nitrogen were transferred to OA directly from the −185 °C storage. For the isolation methods of the IRS isolates see Hanse et al. (2015).
Morphology
Isolates were grown on potato carrot agar (PCA, Crous et al., 2009) and synthetic nutrient-poor agar (SNA, Nirenberg, 1976) at moderate temperatures under CoolWhite fluorescent light with an 8 h photoperiod. After 7 and 14 d the growth rates were measured and the colony characters noted. Colony colours were rated according to Rayner (1970). Morphological descriptions of asexual structures were made for isolates grown on SNA for 7 d. Slides were prepared with the cellotape technique (Schubert et al. 2007) using Titan Ultra Clear Tape (Conglom Inc., Toronto, Canada) and Shear's medium as mounting fluid. Morphological descriptions of sexual structures were made for isolates grown on PCA for 14 d, with 85 % lactic acid as mounting fluid. The mean plus/minus standard deviation values were derived from measurements of 30 structures, with extremes given in parentheses. Photographs of characteristic structures were made with a Zeiss Axio Imager A2 microscope equipped with a Nikon DS-Ri2 high-definition colour camera using differential interference contrast (DIC) optics and the Nikon software NIS-elements D v. 4.50. Adobe Bridge CS5.1 and Adobe Photoshop CS5 Extended, v. 12.1, were used for the final editing and photographic preparation. Nomenclatural data were deposited in MycoBank (Crous et al. 2004).
DNA isolation, PCR and sequencing
DNA extraction was performed using the Wizard® Genomic DNA purification kit (Promega, Madison, USA) according to the manufacturer's instructions. The ITS region, gapdh, tef1 and rpb2 gene regions were amplified and sequenced with respectively the primers V9G (De Hoog and Gerrits van den Ende, 1998)/ITS4 (White et al. 1990), gpd1/gpd2 (Berbee et al. 1999), EF1-728F/EF1-986R (Carbone & Kohn 1999), and RPB2-5F2 (Sung et al. 2007)/fRPB2-7cR (Liu et al. 1999) as described in Woudenberg et al. (2013). The actA gene region was amplified and sequenced with ACT-512F/ACT-783R (Carbone & Kohn 1999) as described in De Gruyter et al. (2009). For the tub2 gene region several primer combinations and PCR programs were tested, but no PCR product could be obtained. The cmdA gene region was amplified and sequenced with the primers CALDF1/CALDR2 (Lawrence et al. 2013). The PCR mixture consisted of 1 μl 50× diluted genomic DNA, 1× NH4+ reaction buffer (Bioline, Luckenwalde, Germany), 2 mM MgCl2, 20 μM of each dNTP, 0.2 μM of each primer and 0.25 U Taq DNA polymerase (Bioline). The PCR conditions consisted of an initial denaturation step of 5 min at 94 °C followed by 35 cycles of 30 s at 94 °C, 30 s at 59 °C and 1 min at 72 °C, and a final elongation step of 7 min at 72 °C. The PCR products were sequenced in both directions using a BigDye Terminator v. 3.1 Cycle Sequencing Kit (Thermo Fisher Scientific, Bleiswijk, the Netherlands) and analysed with an ABI Prism 3730xl DNA Analyser (Thermo Fisher Scientific) according to the manufacturer's instructions. Consensus sequences were computed from forward and reverse sequences using the Bionumerics v. 4.61 software package (Applied Maths, St-Marthens-Latem, Belgium). Generated sequences were deposited in GenBank (Table 1, Supplementary Table 1).
Table 1.
Collection details and GenBank accession numbers of the Stemphylium cultures included in the multi-gene phylogeny.
| Name | Old name1 | Strain number2 | Other collection number2 | Host/Substrate | Country | GenBank accession numbers |
||
|---|---|---|---|---|---|---|---|---|
| ITS | gapdh | cmdA | ||||||
| Alternaria alternata | GV14-634a1 | Chenopodium album | Netherlands | KU850502 | KU850649 | KU850790 | ||
| Stemphylium amaranthi | S. phaseolinaT | CBS 124650 | HSAUP VI1538 | Phaseolus vulgaris | China | KU850503 | KU850650 | KU850791 |
| CBS 124651 | HSAUP VI1682 | Phaseolus vulgaris | China | KU850504 | KU850651 | KU850792 | ||
| CBS 124746T | HSAUPpyf1835 | Amaranthus retroflexus | China | KU850505 | KU850652 | KU850793 | ||
| CBS 124750 | HSAUPpyf1902 | Malus sieversii | Chile | KU850506 | KU850653 | KU850794 | ||
| S. microsporumT | CBS 124753 | HSAUPpyf1904 | Malus sieversii | China | KU850507 | KU850654 | KU850795 | |
| CBS 124984 | HSAUPpyf2018 | Raphanus sativus | China | KU850508 | KU850655 | KU850796 | ||
| S. luffaeT | CBS 124985 | HSAUPpyf2016 | Luffa cylindrica | China | KU850509 | KU850656 | KU850797 | |
| CBS 136589 | E.G.S. 48.098 | Lotus pendunculatus | New Zealand | KU850510 | KU850657 | KU850798 | ||
| Stemphylium armeriae comb. nov. | P. armeriae | CBS 338.73 | Armeria maritima | UK | KU850511 | KU850658 | KU850799 | |
| Stemphylium astragali | CBS 116583ET | E.G.S. 08.174 | Astragalus sp. | Japan | KU850512 | KU850659 | KU850800 | |
| Stemphylium beticola | P. armeriae | CBS 378.54 | Lychnis sp. | Canada | KU850513 | KU850660 | KU850801 | |
| CBS 116599 | UAMH 10489 | Herbaceous dicot | Canada | KU850514 | KU850661 | KU850802 | ||
| CBS 133512 | E.G.S. 30.152 | Pisum sativum | Canada | KU850515 | KU850662 | KU850803 | ||
| CBS 133892 | E.G.S. 38.090 | Lens culinaris | USA | KU850516 | KU850663 | KU850804 | ||
| CBS 136590 | E.G.S. 48.097 | Passiflora edulis | New Zealand | KU850517 | KU850664 | KU850805 | ||
| CBS 136699 | E.G.S. 48.126 | Panax sp. | USA | KU850518 | KU850665 | KU850806 | ||
| CBS 137492 | E.G.S. 50.095 | Spinacia oleracea | USA | KU850519 | KU850666 | KU850807 | ||
| CBS 141024T | GV11-265a | Beta vulgaris | Netherlands | KU850520 | KU850667 | KU850808 | ||
| CBS 141025 | GV12-288-2 | Beta vulgaris | Netherlands | KU850521 | KU850668 | KU850809 | ||
| CBS 141026 | GV12-474-a1 | Beta vulgaris | Netherlands | KU850522 | KU850669 | KU850810 | ||
| GV11-196a1-3 | Beta vulgaris | Netherlands | KU850523 | KU850670 | KU850811 | |||
| GV12-275a1 | Beta vulgaris | Netherlands | KU850524 | KU850671 | KU850812 | |||
| GV12-276a1 | Beta vulgaris | Netherlands | KU850525 | KU850672 | KU850813 | |||
| GV12-287a1 | Beta vulgaris | Netherlands | KU850526 | KU850673 | KU850814 | |||
| GV12-336a1 | Beta vulgaris | Netherlands | KU850527 | KU850674 | KU850815 | |||
| GV12-356a1 | Beta vulgaris | Netherlands | KU850528 | KU850675 | KU850816 | |||
| GV12-367a1 | Beta vulgaris | Netherlands | KU850529 | KU850676 | KU850817 | |||
| GV12-368a1 | Beta vulgaris | Netherlands | KU850530 | KU850677 | KU850818 | |||
| GV12-403a1 | Beta vulgaris | Netherlands | KU850531 | KU850678 | KU850819 | |||
| GV13-425a1 | Beta vulgaris | Netherlands | KU850532 | KU850679 | KU850820 | |||
| GV13-436c2 | Beta vulgaris | Netherlands | KU850533 | KU850680 | KU850821 | |||
| GV14-693a1 | Beta vulgaris | UK | KU850534 | KU850681 | KU850822 | |||
| IFZ2013-024 | Beta vulgaris | Germany | KU850535 | KU850682 | KU850823 | |||
| IFZ2013-035 | Beta vulgaris | Germany | KU850536 | KU850683 | KU850824 | |||
| IFZ2014-020 | Beta vulgaris | Germany | KU850537 | KU850684 | KU850825 | |||
| Stemphylium botryosum | CBS 714.68T | E.G.S. 04.118c; IMI 135456; MUCL 11717; QM 1379 | Medicago sativa | Canada | KC584238 | AF443881 | KU850826 | |
| CBS 116596 | E.G.S. 08.069; QM 7066 | Medicago sativa | USA | KU850538 | KU850685 | KU850827 | ||
| Stemphylium callistephi | CBS 527.50T | Callistephus chinensis | USA | KU850539 | KU850686 | KU850828 | ||
| Stemphylium canadense sp. nov. | CBS 116602T | UAMH 10491 | Salicornia sp. | Canada | KU850641 | KU850782 | KU850932 | |
| CBS 118081 | UAMH 10491 | Salicornia sp. | Canada | KU850642 | KU850783 | KU850933 | ||
| Stemphylium chrysanthemicola sp. nov. | CBS 117255T | E.G.S. 31.008 | Chrysanthemum sp. | New Zealand | KU850640 | KU850781 | KU850931 | |
| Stemphylium drummondii | CBS 346.83T | Phlox drummondii | Germany | GQ395365 | KU850687 | KU850829 | ||
| Stemphylium eturmiunum | S. vesicarium | CBS 668.80 | Solanum lycopersicum | Greece | KU850540 | KU850688 | KU850830 | |
| CBS 109845T | E.G.S. 29.099; IMI 386969 | Solanum lycopersicum | New Zealand | KU850541 | KU850689 | KU850831 | ||
| CBS 122124 | Asphodelus aestivus | Greece | KU850542 | KU850690 | KU850832 | |||
| S. variabilisT | CBS 122641 | HSAUPIVI1508 | Allium sativum | France | KU850543 | KU850691 | KU850833 | |
| CBS 124652 | HSAUP1559 | Solanum lycopersicum | China | KU850544 | KU850692 | KU850834 | ||
| S. vesicarium | CBS 133528 | E.G.S. 30.002 | Allium sativum | India | KU850545 | KU850693 | KU850835 | |
| S. capsiciT | CBS 138495 | E.G.S. 53.123 | Capsicum annuum | China | KU850546 | KU850694 | KU850836 | |
| Stemphylium gracilariae | P. lycopersici | CBS 308.36 | ATCC 10737 | Solanum lycopersicum | USA | KU850547 | KU850695 | KU850837 |
| P. herbarum f. lactucumT | CBS 273.55 | Lactuca sp. | Unknown | KU850548 | KU850696 | KU850838 | ||
| CBS 482.90T | E.G.S. 37.073; ATCC 669721 | Gracilaria sp. | Israel | KU850549 | AF443883 | KU850839 | ||
| CBS 115179 | STE-U 5216; CPC 5216 | Leucospermum sp. | Spain | KU850550 | KU850697 | KU850840 | ||
| CBS 115180 | STE-U 5217; CPC 5217 | Leucospermum sp. | Spain | KU850551 | KU850698 | KU850841 | ||
| S. cucumisT | CBS 125060 | HSAUPpyf2377 | Cucumis melo | China | KU850552 | KU850699 | KU850842 | |
| Stemphylium halophilum comb. nov. | CBS 337.73T | Limonium vulgare | UK | KU850553 | KU850700 | KU850843 | ||
| CBS 410.73 | Armeria maritima | UK | KU850554 | KU850701 | KU850844 | |||
| Stemphylium ixeridis | CBS 124748T | Ixeris denticulata | China | KU850590 | KU850737 | KU850881 | ||
| Stemphylium lancipes | CBS 101217 | Aquilegia sp. | New Zealand | KU850594 | KU850741 | KU850885 | ||
| CBS 116584 | E.G.S. 46.182 | Aquilegia sp. | New Zealand | KU850595 | AF443886 | KU850886 | ||
| CBS 133314ET | E.G.S. 10.022 | Aquilegia canadensis | USA | KU850596 | KU850742 | KU850887 | ||
| Stemphylium loti | CBS 407.54T | ATCC 11718 | Lotus corniculatus | USA | KU850597 | KU850743 | KU850888 | |
| Stemphylium lucomagnoense sp. nov. | P. gigaspora | CBS 116601T | E.G.S. 37.017 | Minuartia hybrida | Switzerland | KU850629 | KU850770 | KU850920 |
| Stemphylium lycii | CBS 115192 | STE-U 5223; CPC 5223 | Protea cynaroides | Portugal | KU850598 | KU850744 | KU850889 | |
| CBS 116582 | E.G.S. 48.089 | Pistacia vera | USA | KU850599 | KU850745 | KU850890 | ||
| CBS 124982 | HSAUPpyf1828 | Apium graveolens | China | KU850600 | KU850746 | KU850891 | ||
| CBS 125240 | HSAUP1826 | Cucurbita moschata | China | KU850601 | KU850747 | KU850892 | ||
| CBS 125241T | HSAUP 1833 | Lycium chinense | China | KU850602 | KU850748 | KU850893 | ||
| Stemphylium lycopersici | S. lancipes | CBS 333.73 | PD 72/1118 | Platycodon sp. | Netherlands | KU850603 | KU850749 | KU850894 |
| S. vesicarium | CBS 436.76 | Unknown | Indonesia | KU850604 | KU850750 | KU850895 | ||
| S. lancipes | CBS 463.78 | Solanum tuberosum | Peru | KU850605 | KU850751 | KU850896 | ||
| CBS 321.87 | Solanum lycopersicum | Senegal | KU850606 | KU850752 | KU850897 | |||
| S. xanthosomatisT | CBS 116585 | E.G.S. 17.137 | Xanthosoma sagittifolium | New Caledonia | KU850607 | AY317010 | KU850898 | |
| CBS 116587 | E.G.S. 46.001 | Solanum lycopersicum | Dominican Republic | KU850608 | KU850753 | KU850899 | ||
| S. sophoraeT | CBS 120325 | Sophora microphylla | China | KU850609 | KU850754 | KU850900 | ||
| S. oblongumT | CBS 120326 | Gossypium hirsutum | China | KU850610 | KU850755 | KU850901 | ||
| CBS 122639NT | HSAUPV0893 | Solanum lycopersicum | China | KU850611 | KU850756 | KU850902 | ||
| S. pyrinaT | CBS 122803 | HSAUP wy0006 | Pyrus sinkiangensis | China | KU850612 | KU850757 | KU850903 | |
| CBS 123008 | HSAUP0475 | Brassica pekinensis | China | KU850613 | KU850758 | KU850904 | ||
| S. pruniT | CBS 124980 | HSAUPIII00159; E.G.S. 53.121 | Prunus persica | China | KU850614 | KU850759 | KU850905 | |
| S. plantaginisT | CBS 124981 | HSAUPIII00532 | Plantago major | China | KU850615 | KU850760 | KU850906 | |
| CBS 124983 | HSAUPpyf1842(2) | Clinopodium polycephalum | China | KU850616 | KU850761 | KU850907 | ||
| CBS 135778 | E.G.S. 46.183 | Salvia officinalis | New Zealand | KU850617 | AY317026 | KU850908 | ||
| Stemphylium majusculum | CBS 717.68T | E.G.S. 29.094; ATCC 18520; IMI 135459; MUCL 11720; MUCL 18568; NRRL 5269; QM 8382 | Lathyrus maritimus | USA | KU850618 | AF443891 | KU850909 | |
| CBS 133424 | E.G.S. 16.068; IMI 135459; QM 8382 | Lathyrus maritimus | USA | KU850619 | AF443891 | KU850910 | ||
| Stemphylium novae-zelandiae sp. nov. | CBS 138157 | E.G.S. 52.147 | Avicennia resinifera | New Zealand | KU850630 | KU850771 | KU850921 | |
| CBS 138295T | E.G.S. 52.148 | Avicennia resinifera | New Zealand | KU850631 | KU850772 | KU850922 | ||
| Stemphylium paludiscirpi | CBS 109842T | E.G.S. 31.016; IMI 386966 | Scirpus sp. | USA | KU850620 | KU850762 | KU850911 | |
| Stemphylium sarciniforme | CBS 335.33 | Trifolium pratense | USA | KU850621 | KU850763 | KU850912 | ||
| CBS 364.49 | ATCC 10828 | Trifolium pratense | USA | KU850622 | KU850764 | KU850913 | ||
| “S. kaiseri” | CBS 110049 | E.G.S. 31.011 | Cicer arietinum | Iran | KU850591 | KU850738 | KU850882 | |
| CBS 116579 | E.G.S. 38.121 | Trifolium pratense | USA | KU850623 | AF443892 | KU850914 | ||
| CBS 116581 | E.G.S. 29.188 | Cicer arietinum | Iran | KU850592 | KU850739 | KU850883 | ||
| CBS 133723 | E.G.S. 36.006 | Trifolium pratense | USA | KU850624 | KU850765 | KU850915 | ||
| CBS 136810 | E.G.S. 49.033 | Cicer arietinum | Iran | KU850593 | KU850740 | KU850884 | ||
| CBS 138345 | E.G.S. 53.018 | Trifolium pratense | New Zealand | KU850625 | KU850766 | KU850916 | ||
| Stemphylium simmonsii sp. nov. | S. globuliferum | CBS 716.68 | ATCC 18518; IMI 135458; MUCL 11718; QM 8729 | Commelina sp. | USA | KU850632 | KU850773 | KU850923 |
| CBS 116598 | UAMH 10487 | Phragmitis sp. | Canada | KU850633 | KU850774 | KU850924 | ||
| CBS 116603 | UAMH 10493 | Lactuca muralis | Canada | KU850634 | KU850775 | KU850925 | ||
| CBS 116604 | UAMH 10494 | Guem macrophyllum | Canada | KU850635 | KU850776 | KU850926 | ||
| CBS 133515 | E.G.S. 30.153 | Solanum lycopersicum | Canada | KU850636 | KU850777 | KU850927 | ||
| CBS 133518T | E.G.S. 30.154 | Fragaria sp. | Canada | KU850637 | KU850778 | KU850928 | ||
| S. globuliferum | CBS 133894 | E.G.S. 38.115 | Trifolium pratense | USA | KU850638 | KU850779 | KU850929 | |
| S. globuliferum | CBS 134496 | E.G.S. 42.138 | Malus sylvestris | Australia | KU850639 | KU850780 | KU850930 | |
| Stemphylium solani | CBS 408.54 | ATCC 11128 | Solanum lycopersicum | USA | KU850626 | KU850767 | KU850917 | |
| CBS 116586ET | E.G.S. 41.135 | Solanum lycopersicum | USA | KU850627 | KU850768 | KU850918 | ||
| CBS 118082 | E.G.S. 42.055; CBS 134293 | Euphorbia marginata | USA | KU850628 | KU850769 | KU850919 | ||
| Stemphylium symphyti | CBS 115268T | Symphytum uplandicum | USA | KU850643 | KU850784 | KU850934 | ||
| CBS 118796 | Symphytum uplandicum | New Zealand | KU850644 | KU850785 | KU850935 | |||
| CBS 138069 | E.G.S. 52.041 | Borago officinalis | New Zealand | KU850645 | KU850786 | KU850936 | ||
| CBS 138070 | E.G.S. 52.042 | Borago officinalis | New Zealand | KU850646 | KU850787 | KU850937 | ||
| Stemphylium trifolii | CBS 116580T | E.G.S. 12.142 | Trifolium repens | USA | KU850647 | KU850788 | KU850938 | |
| Stemphylium triglochinicola | CBS 718.68T | ATCC 18516; IMI 122774ii; IMI 135460; MUCL 11716; MUCL 18569; NRRL 5270; QM 8752 | Triglochin maritima | UK | KU850648 | KU850789 | KU850939 | |
| Stemphylium vesicarium | CBS 155.24 | Allium sp. | Unknown | KU850555 | KU850702 | KU850845 | ||
| CBS 157.24 | Abies sp. | Unknown | KU850556 | KU850703 | KU850846 | |||
| P. pomorumNT | CBS 184.25 | Malus domestica | UK | KU850557 | KU850704 | KU850847 | ||
| CBS 273.31 | Unknown | Unknown | KU850558 | KU850705 | KU850848 | |||
| CBS 274.31 | Phaseolus vulgaris | Unknown | KU850559 | KU850706 | KU850849 | |||
| CBS 307.36 | Citrus sp. | Tunisia | KU850560 | KU850707 | KU850850 | |||
| CBS 156.45 | Dianthus caryophyllus | Netherlands | KU850561 | KU850708 | KU850851 | |||
| CBS 322.49 | Lathyrus odoratus | Netherlands | KU850562 | KU850709 | KU850852 | |||
| CBS 370.51 | Trigonella foenum-graecum | Netherlands | KU850563 | KU850710 | KU850853 | |||
| CBS 368.59 | Linum usitatissimum | Denmark | KU850564 | KU850711 | KU850854 | |||
| S. vesicarium | CBS 715.68 | E.G.S. 12.171; ATCC 18521; DAOM 48576a; IMI 135457; MUCL 11719; NRRL 5 | Pisum sativum | Canada | KU850565 | KU850712 | KU850855 | |
| CBS 406.76 | Solanum lycopersicum | Germany | KU850566 | KU850713 | KU850856 | |||
| CBS 205.82 | Lunaria annua | Netherlands | KU850567 | KU850714 | KU850857 | |||
| S. herbarumT | CBS 191.86 | E.G.S. 36.138; IMI 276975 | Medicago sativa | India | KC584239 | AF443884 | KU850858 | |
| S. alfalfaeT | CBS 192.86 | E.G.S. 36.088; IMI 269683 | Medicago sativa | Australia | KU850568 | KU850715 | KU850859 | |
| S. vesicarium | CBS 311.92 | Allium cepa | Netherlands | KU850569 | KU850716 | KU850860 | ||
| S. vesicarium | CBS 486.92 | Allium cepa | Netherlands | KU850570 | KU850717 | KU850861 | ||
| P. sedicolaT | CBS 109843 | E.G.S. 48.095; IMI 386967 | Sedum spectabile | New Zealand | KU850571 | KU850718 | KU850862 | |
| P. tomatonisT | CBS 109844 | E.G.S. 29.089; IMI 386968 | Solanum lycopersicum | USA | KU850572 | KU850719 | KU850863 | |
| CBS 115182 | STE-U 5229; CPC 5229 | Leucadendron sp. | South Africa | KU850573 | KU850720 | KU850864 | ||
| CBS 115204 | STE-U 5224; CPC 5224 | Leucadendron sp. | Portugal | KU850574 | KU850721 | KU850865 | ||
| S. maliT | CBS 122640 | HSAUP VIwy1542 | Malus sieversii | China | KU850575 | KU850722 | KU850866 | |
| CBS 123005 | HSAUPV 0366 | Fabaceae | China | KU850576 | KU850723 | KU850867 | ||
| S. alfalfae | CBS 123803 | HSAUP 0366 | Allium sativum | China | KU850577 | KU850724 | KU850868 | |
| S. eturmiunum | CBS 124279 | Malus domestica | Denmark | KU850578 | KU850725 | KU850869 | ||
| S. cremanthodiiT | CBS 124747 | HSAUPpyf1830(1) | Cremanthodium discoideum | China | KU850579 | KU850726 | KU850870 | |
| S. brassicicolaT | CBS 124749 | HSAUPpyf1858(2) | Brassica pekinensis | China | KU850580 | KU850727 | KU850871 | |
| CBS 124751 | HSAUPpyf2328 | Pyrus sinkiangensis | China | KU850581 | KU850728 | KU850872 | ||
| CBS 124752 | HSAUPpyf2371 | Populus tomentosa | China | KU850582 | KU850729 | KU850873 | ||
| CBS 125242 | HSAUP 1914 | Dahlia pinnata | China | KU850583 | KU850730 | KU850874 | ||
| S. tomatonis | CBS 133474 | E.G.S. 29.089 | Solanum lycopersicum | USA | KU850584 | KU850731 | KU850875 | |
| S. alfalfae | CBS 133737 | E.G.S. 36.088; IMI 269683 | Medicago sativa | Australia | KU850585 | KU850732 | KU850876 | |
| S. alfalfae | CBS 133905 | E.G.S. 39.127 | Medicago sativa | USA | KU850586 | KU850733 | KU850877 | |
| S. alfalfae | CBS 133914 | E.G.S. 40.038 | Medicago sativa | USA | KU850587 | KU850734 | KU850878 | |
| CBS 138138 | E.G.S. 52.113 | Lonicera sp. | Netherlands | KU850588 | KU850735 | KU850879 | ||
| GV11-355-a1-2 | Beta vulgaris | Netherlands | KU850589 | KU850736 | KU850880 | |||
The T indicates the ex-type isolate of the synonymised species.
ATCC: American Type Culture Collection, Manassas, VA, USA; CBS: Culture Collection of the Westerdijk Fungal Biodiversity Institute, Utrecht, the Netherlands; CPC: Personal collection of P.W. Crous, Utrecht, the Netherlands; DAOM: Canadian Collection of Fungal Cultures, Ottawa, Canada; E.G.S.: Personal collection of Dr. E.G. Simmons; HSAUP: Department of Plant Pathology, Shandong Agricultural University, China; IMI: Culture Collection of CABI Europe-UK, Egham, UK; MUCL: (Agro)Industrial Fungi and Yeast Collection of the Belgian Co-ordinated Collections of Micro-organisms (BCCM), Louvain-la Neuve, Belgium; NRRL: ARS Culture Collection, U.S. Department of Agriculture, Peoria, IL, USA; PD: Plant Protection Service, Wageningen, the Netherlands; QM: Quarter Master Culture Collection, Amherst, MA, USA; STE-U: Department of Plant Pathology, University of Stellenbosch, South Africa; UAMH: University of Toronto, UAMH Centre for Global Microfungal Biodiversity, Toronto, Canada; Ex-epitype, -type, and -neotype isolates are indicated with ET, T and NT, respectively.
Identification of best loci
Based on the ITS sequence results and former sequence data (Inderbitzin et al. 2009), seven isolates representing clade 10 (Fig. 1), namely CBS 378.54, CBS 116598, CBS 116599, CBS 134496, CBS 136590, GV11-196-a1-3 and IFZ2013-024, were selected to determine which gene would be the most informative in distinguishing species within this clade. In addition to ITS, the actA, cmdA, gapdh, rpb2 and tef1 gene regions were amplified and sequenced as described above. Unfortunately the beta-tubulin PCRs did not give any results, even when following previously published PCR primers and methods (Bt2a/Bt2b, Glass & Donaldson 1995) which are supposed to work on Stemphylium species (Lawrence et al. 2013). A sequence comparison from the five additional gene regions of the seven selected isolates was made in Bionumerics v. 4.61 (Applied Maths) and by eye (Table 2).
Fig. 1.
Maximum likelihood tree based on the ITS sequences of 357 isolates. The RAxML bootstrap support values > 75 % (BS) and Bayesian posterior probabilities > 0.95 (PP) are given at the nodes. Thickened lines indicate a BS of 100 % and a PP of 1.0. Ex-type strain numbers are in bold face and indicated with T (or NT or ET when respectively neo- or epi-typified in this study). Species names in bold face represent unconfirmed species names. The tree was rooted to A. alternata GV14-634a1.
Table 2.
Gene test on selected isolates from clade 10 (see Fig. 1). The numbers in the body of the table represent the number of the sequence allele for the given locus.
| Isolate number | Original name | Host | Location | ITS1 | actA | rpb2 | tef1 | cmdA | gapdh | tub22,3 |
|---|---|---|---|---|---|---|---|---|---|---|
| CBS 116599 | Pleospora sp. | Herbaceous dicot | Canada | 1 | 1 | 1 | 1 | 1 | 1 | np |
| GV11-196-a1-3 | Stemphylium sp. | Beta vulgaris | Netherlands | 1 | 1 | 1 | 1 | 1 | 1 | np |
| CBS 378.54 | P. armeriae | Lychnis sp. | Canada | 1 | 1 | 1 | 1 | 1 | 2 | np |
| IFZ2013-024 | Stemphylium sp. | Beta vulgaris | Germany | 1 | 1 | 1 | 1 | 2 | 1 | np |
| CBS 136590 | Pleospora sp. | Passiflora edulis | New Zealand | 1 | 1 | 1 | 1 | 2 | 3 | np |
| CBS 116598 | Pleospora sp. | Phragmitis sp. | Canada | 2 | 2 | 2 | 2 | 3 | 4 | np |
| CBS 134496 | S. globuliferum | Malus sylvestris | Australia | 2 | 2 | np3 | 3 | 4 | 5 | np |
ITS difference is only in two T-repeat regions.
tub2 gave no PCR products, despite of testing different primer combinations and PCR conditions.
np: no PCR product.
Phylogenetic analyses
In Bionumerics v. 4.61 (Applied Maths), a quick UPGMA phylogeny was constructed from the ITS sequences of the 441 included isolates to assign them to clusters of closely related or identical isolates. For those isolates belonging to the Stemphylium clade, a multiple sequence alignment of the ITS sequences was generated with MAFFT v. 7.271 (http://mafft.cbrc.jp/alignment/server/index.html) using the FFT-NS-i method. With Findmodel (http://www.hiv.lanl.gov/content/sequence/findmodel/findmodel.html) the best nucleotide substitution model was determined. Bayesian analyses were performed with MrBayes v. 3.2.1 (Huelsenbeck and Ronquist, 2001, Ronquist and Huelsenbeck, 2003). The Markov Chain Monte Carlo (MCMC) analysis used four chains and started from a random tree topology. The sample frequency was set at 1 000 and the temperature value of the heated chain was set at 0.1. The run stopped when the average standard deviation of split frequencies reached below 0.01. Burn-in was set to 25 % after which the likelihood values were stationary. Tracer v. 1.5.0 (Rambaut & Drummond 2009) was used to confirm the convergence of chains. A maximum-likelihood analysis including 500 bootstrap replicates using RAxML v. 7.2.6 (Stamatakis & Alachiotis 2010) was also run. Sequences of A. alternata (GV14-634-a1) were used as outgroup. The same steps were applied to generate the multi-gene phylogeny, on both the single gene alignments and the multi-gene alignment, with the only difference being that the L-INS-I method was used in MAFFT v. 7.271 for generating the multiple sequence alignment. The resulting trees were printed with TreeView v. 1.6.6 (Page 1996) and, together with the alignments, deposited into TreeBASE (http://www.treebase.org).
Results
Identification of best loci
The ITS, rpb2 and actA gene regions were the least informative, since only two sequence alleles were observed, all splitting the seven isolates in the same two allele groups (Table 2). For the ITS sequences the sequence difference between the two allele groups is in two T-repeats, which are not considered informative by standard phylogeny software. Differences in repeat regions are normally regarded as sequence errors, and are not included in calculations for phylogenetic trees. However, when these differences are compared with the results from the other gene information, the difference in number of T-repeats does seem to be relevant in this case. The tef1 gene region showed three different sequence alleles, additionally splitting CBS 134496 from the second allele group (Table 2). The cmdA and gapdh gene regions seem to have the highest potential of being most informative as respectively four and five different sequence alleles were observed (Table 2). Based on these results the cmdA and gapdh gene regions were sequenced for a selection of 150 isolates (including the outgroup isolate GV14-634-a1), representing all possible species in Stemphylium based on ITS sequence data and ecological data (Table 1).
ITS phylogeny
The initial UPGMA phylogeny constructed in Bionumerics v. 4.61 placed 356 isolates in the Stemphylium clade (data not shown). Together with the outgroup-isolate GV14-634-a1, an Alternaria alternata isolated from sugar beet, these 357 isolates form the dataset of the Stemphylium ITS phylogeny. The aligned sequences contained 545 nucleotides with 101 unique site patterns. The TrN model with a gamma-distributed rate variation was suggested as model for the Bayesian analysis. The average standard deviation of split frequencies never reached below 0.01 while running MrBayes at different temperature values. Therefore, the temperature value was lowered to 0.05, and the run was stopped after 5 M generations for which the convergence of chains was confirmed in Tracer. After discarding the burn-in phase trees, the runs resulted in 7 502 trees from which the majority rule consensus tree and posterior probabilities were calculated.
The phylogeny based on the ITS sequences divides the 356 Stemphylium isolates into 22 clades (Fig. 1). In clade 10, 33 isolates were found, 18 sugar beet isolates and 15 isolates from the CBS collection. The three sugar beet isolates from Germany and the one from the UK cluster here amidst the Dutch sugar beet isolates. The phylogenetic tree shows a straight vertical line for this clade, implying that the sequences are phylogenetically identical. However, by eye two different sequences are observed with a T repeat of 7 nt starting on position 139 in the ITS alignment (deposited in TreeBASE) in combination with a T repeat of 6 nt starting on position 491, versus a T repeat of 6 nt starting on position 139 in combination with a T repeat of 7 nt starting on position 491 in the alignment. Although not phylogenetically recognised, this difference splits the CBS isolates in two subgroups, with seven isolates, CBS 378.54, CBS 116599, CBS 133512, CBS 133892, CBS 136590, CBS 136699 and CBS 137492, having an ITS sequence identical to the sugar beet isolates.
Multi-gene phylogeny
From the ITS phylogeny 149 isolates were selected to represent the genus Stemphylium and the partial gapdh and cmdA gene sequences were added to the existing ITS sequence data (Table 1). The selection included all ex-type isolates, all isolates from potential new species, and at least one representative per clade of the ITS phylogeny. The aligned sequences of the ITS (545 characters), gapdh (595 characters) and cmdA (860 characters) gene regions of the 150 isolates (including the outgroup isolate) had a total length of 2 000 characters, with respectively 95, 199, and 317 unique site patterns. The HKY model with a gamma-distributed rate variation was suggested as model for the ITS and gapdh alignments and the GTR model with a gamma-distributed rate variation for the cmdA alignment. After discarding the burn-in phase trees, the multi-gene Bayesian analysis resulted in 6 978 trees from which the majority rule consensus tree and posterior probabilities were calculated.
The multi-gene phylogeny divided the isolates in 28 species clades (Fig. 2). New species descriptions are provided in the taxonomy section below.
Fig. 2.
Maximum likelihood tree based on the combined ITS, gapdh and cmdA sequence alignment of 150 isolates. The RAxML bootstrap support values > 75 % (BS) and Bayesian posterior probabilities > 0.95 (PP) are given at the nodes. Thickened lines indicate a BS of 100 % and a PP of 1.0. Species names between parentheses represent synonymised species names. Ex-type strains are in bold face and indicated with T (or NT or ET when respectively neo- or epi-typified in this study). The tree was rooted to A. alternata GV14-634a1.
Taxonomy
As a result of the multi-gene phylogenetic analysis, 22 species names are synonymised, and two new combinations and five new species proposed. Synonyms and descriptions of the new species and new combinations are provided below.
Stemphylium amaranthi Y.F. Pei & X.G. Zhang, Mycotaxon 109: 495. 2009.
Synonyms: Stemphylium microsporum Y.F. Pei & X.G. Zhang, Mycotaxon 111: 171. 2010.
Stemphylium phaseolina Yong Wang bis & X.G. Zhang, Mycologia 102: 709. 2010.
Stemphylium luffae Y.F. Pei & X.G. Zhang, Mycol. Progr. 10: 166. 2011.
Specimens examined: China, Hebei Province, Zhaoxian, from Phaseolus vulgaris leaves, Sep. 2006, Y. Wang (culture ex-type of S. phaseolina CBS 124650); Shandong Province, Tai'an, from Phaseolus vulgaris leaves, Oct. 2006, Y. Wang, CBS 124651; Sinkiang Province, Korla, from Amaranthus retroflexus leaves, 17 Oct. 2008, Y.F. Pei (culture ex-type CBS 124746); Sinkiang Province, Yili, from Luffa cylindrica leaves, collection date unknown, Y.F. Pei (culture ex-type of S. luffae CBS 124985); Sinkiang Province, Yili, from Malus sieverii leaves, 10 Aug. 2009, Y.F. Pei, (culture ex-type of S. microsporum CBS 124753).
Notes: The species S. amaranthi and S. microsporum were described based on morphological data only (Pei et al., 2009, Pei et al., 2010), and no sequence data were available on GenBank. Their morphological descriptions differ, especially their spore sizes (22–35 × 10–19 for S. amaranthi versus 15–24 × 9–15 for S. microsporum). However, our measurements of the ex-type isolate of S. microsporum (CBS 124753) resulted in a spore size of (24.5–)27–35 (−42) × (12–)13.5–16(–18), which would fit the description of S. amaranthi. Both S. luffae and S. phaseolina are described based on morphological and molecular data, although in the later description of S. luffae, the sequences of S. phaseolina are not incorporated in the phylogenetic tree. The published ITS sequences of the ex-type isolate of S. luffae and S. phaseolina (GU182943 and GQ395369 respectively) are 100 % identical, but their gapdh sequences (GU182938 and GQ395374 respectively) are only 98 % identical. However, the gapdh sequence we obtained from the ex-type strain of S. luffae (KU850656) is only 99 % identical to the originally published sequence (GU182938), and also the gapdh sequence we obtained from the ex-type strain of S. phaseolina (KU850650) is only 99 % identical to the originally published sequence (GQ395374). This led to a 100 % identity of the gapdh sequences of the ex-type isolates of S. luffae and S. phaseolina. When looking at the described morphological characters, S. luffae and S. phaseolina also fit in the morphological species description of S. amaranthi. The only remark is that S. luffae and S. phaseolina are described with a conspicuously punctate conidial wall, although S. amaranthi was originally described with an inconspicuously micromaculate conidial wall.
Stemphylium armeriae (Corda) Woudenb. & Crous, comb. nov. MycoBank MB820657.
Basionym: Sphaeria armeriae Corda, Icon. Fungorum hucusque Cogn. 4: 41, t. 8:119. 1840.
Synonyms: Pleospora armeriae (Corda) Ces. & De Not., Comment. Soc. Crittog. Ital. 1: 218. 1863.
Pleospora herbarum f. armeriae (Corda) Sacc., Syll. Fungorum (Abellini) 2: 247. 1883.
Pyrenophora armeriae (Corda) Berl., Nuovo Giorn. Bot. Ital. 20: 242. 1888.
Pleospora herbarum var. armeriae (Corda) J. Webster, Trans. Brit. Mycol. Soc. 44: 418. 1961.
Specimen examined: UK, England, Devon, Budleigh Salterton Salt Marsh, from Armeria maritima, 12 Aug. 1972, J. Webster, CBS 338.73.
Notes: Sphaeria armeriae was described from flower stalks of Armeria vulgaris (= A. maritima) in Germany (Corda 1840). Later it was transferred to the genus Pleospora (Cesati & De Notaris 1863). Saccardo (1883) treated it as a form of P. herbarum, while others treated it as synonym of P. herbarum (Winter, 1887, Müller, 1951). Wehmeyer (1952) and Webster & Lucas (1961) both studied the holotype specimen (Herb A.C.I. Corda no. 155637), and concluded that it was immature; no fully mature ascospores could be found. A study comparing P. herbarum var. armeriae isolates from Armeria with cultures of P. herbarum from other hosts in culture, showed conidia similar to the Stemphylium type (Webster & Lucas 1961). However, they did observe a difference in the ascus width between the two species, with var. armeriae having wider asci. Isolate CBS 338.73 was deposited in the CBS collection as S. herbarum var. armeriae by J. Webster, the author of this variety. We therefore propose the new combination for Sphaeria armeriae as Stemphylium armeriae.
Stemphylium astragali (Yoshii) W. Yamam., Trans. Mycol. Soc. Japan 2: 92. 1960.
Basionym: Thyrospora astragali Yoshii, J. Pl. Protect. 16: 536. 1929.
Specimen and material examined: Japan, (lectotype designated here of T. astragali, Journal of Plant Protection, Tokyo 16: illustration on page 534, 1929, Yoshii H, MBT375877); Fukuoka, from Astragalus sp., collection date unknown, H. Yoshii, (epitype designated here of T. astragali CBS H-23050, MBT375505, culture ex-epitype CBS 116583 = E.G.S. 08.174).
Notes: Stemphylium astragali, with Thyrospora astragali as basionym, does not refer to a holotype specimen in its original description (Yoshii 1929), nor could we locate one. However, in 1956 Yoshii sent an isolate (CBS 116583) named Thyrospora astragali to Emory G. Simmons, who recognised this as authentic isolate. Since no holotype specimen is known, we designated the original illustration on page 534 as lectotype, and propose CBS 116583 as ex-epitype culture of Thyrospora astragali here.
Stemphylium beticola Woudenb. & Hanse, Persoonia 36: 403. 2016. Fig. 3.
Fig. 3.
Stemphylium beticola (CBS 141024). A, C. Conidiophores and conidia. B. Conidia. D–E. Ascoma. Scale bars: A–C = 10 μm; D–E = 100 μm.
Conidiophores solitary, straight to flexuous, occasionally branched, septate, smooth, pale brown, (41–)45–72(–88) × 4–5 μm, bearing 1–3 darkened percurrent rejuvenation sites. Conidiogenous cells swollen at the apex, darkened, 5–6 μm wide. Conidia solitary, conidium body pale olive-brown, verrucose, ellipsoid to cylindrical, (21–)22–26(–30) × (13–)14–16(–18) μm, L/W = 1.6, with 2–4 transverse septa and 1–3 longitudinal and 0–2 oblique septa per transverse sector. Constricted at 1–2 darkened transverse septa. Occasionally with an apical secondary conidiophore. Immature ascomata of sexual morph observed on agar, pseudothecia globose, ellipsoid or irregular, single or aggregated, ranging from 100 to 300 μm tall (from Crous et al. 2016).
Culture characteristics: After 7 d cultures on SNA flat, fimbriate, colourless with abundant black ascomatal initials in the agar, aerial mycelium is sparse, white, colonies reaching 45–55 mm diam; cultures on PCA flat, entire to undulate, colourless with abundant black ascomata in the agar, aerial mycelium is sparse floccose, (greenish) olivaceous; colonies reaching 50–60 mm diam.
Specimens examined: Netherlands, Noord-Brabant, Langenboom, on leaves of Beta vulgaris, 17 Aug. 2011, P. Wilting, (holotype CBS H-22486, culture ex-type CBS 141024 = GV11-265a); Groningen, Nieuwe Pekela, on leaves of Beta vulgaris, 17 July 2012, J. Lingbeek, GV12-288-2 = CBS 141025; Drenthe, Eerste Exloërmond, on leaves of Beta vulgaris, 11 Sept. 2012, B. Hanse, CBS 141026 = GV12-474a1.
Notes: Stemphylium beticola causes a leaf spot disease on sugar beet (Beta vulgaris) (Hanse et al. 2015), which has been detected in multiple European countries (Crous et al. 2016). Host range tests demonstrated that the species was not restricted to Beta vulgaris (Hanse et al. 2015), which is confirmed in this study by the clustering of multiple isolates from different hosts in the S. beticola clade. This study further shows that S. beticola also occurs in the USA, Canada and New Zealand. Molecularly it is closely related to S. simmonsii, another species with a broad host range, but which does not include isolates from Europe. They can be separated morphologically by their ascomata, which have dark hyphal outgrows in S. simmonsii.
Stemphylium canadense Woudenb. & Crous, sp. nov. MycoBank MB820658. Fig. 4.
Fig. 4.
Stemphylium canadense sp. nov. (CBS 116602). A–D. Conidiophores and conidia. E. Conidia. Scale bars = 10 μm.
Etymology: Named after the country from which it was collected, Canada.
Conidiophores solitary, straight to flexuous, occasionally branched, septate, smooth, light olive brown, (46–)62.5–107(–137.5) × (3–)4–5.5(–7) μm, bearing 1–2 thickened, darkened, percurrent rejuvenation sites. Conidiogenous cells swollen at the apex, darkened, (5.5–)6.5–8.5(–10.5) μm wide. Conidia solitary, conidium body pale olive brown, verrucose, ovoid with pointed apex, (37.5–)43.5–59(–71.5) × (13.5–)15–18(–20) μm, L/W = 3.1, with 5–8 transverse septa and 1–2(–3) longitudinal or oblique septa per transverse sector. Constricted at multiple darkened transverse septa. Sexual morph not observed.
Culture characteristics: After 7 d cultures on SNA flat, entire, aerial mycelium is scarce, woolly, white, colonies colourless, with pale olivaceous grey centre, colonies 20–29 mm diam; cultures after 7 d on PCA effuse, entire, aerial mycelium scarce, fine felty to woolly, olivaceous grey, colonies colourless with greenish olivaceous zones, colonies reaching 20–31 mm diam.
Specimens examined: Canada, British Colombia, near Roberts Bank Port, from Salicornia sp., 24 May 2001, A. & R. Bandoni (holotype F 14991, culture ex-type CBS 116602 = UAMH 10491); British Colombia, Hornby Island, beach of Cape Gurney, from Salicornia sp., collection date unknown, A. & R. Bandoni, CBS 118081 = UAMH 10492.
Notes: Stemphylium canadense includes two cultures (CBS 116602 and CBS 118081) isolated from Salicornia spp. in Canada. In fig. 2 of Inderbitzin et al. (2009) these two isolates were already mentioned as an unnamed species in Clade E1. A Pleospora sp. has already been described from Salicornia sp. in France, namely Pleospora salicorniae (Dangeard 1888). However no sexual morph was observed in our isolates of Stemphylium canadense, and therefore we could not confirm conspecificity.
Stemphylium chrysanthemicola Woudenb. & Crous, sp. nov. MycoBank MB820659. Fig. 5.
Fig. 5.
Stemphylium chrysanthemicola sp. nov. (CBS 117255). A–B. Conidiophores and conidia. C–D. Conidia. E. Hyphal plaques. Scale bars = 10 μm.
Etymology: Named after the host genus from which it was collected, Chrysanthemum.
Conidiophores solitary, straight to curved, occasionally branched, septate, smooth, sub-hyaline, (71–)106–186(–282) × (3–)4–5 μm, bearing multiple darkened percurrent rejuvenation sites. Conidiogenous cells swollen at the apex, sub-hyaline, (5–)5.5–7(–7.5) μm wide. Conidia solitary, conidium body brown, verrucose, ellipsoid to cylindrical, (24.5–)26–29(–30.5) × (11–)13.5–15.5(–16.5) μm, L/W = 1.9, with 2–3 transverse septa and 1(–2) longitudinal or oblique septa per transverse sector. Constricted at 1–2 darkened transverse septa. Forms hyphal plaques at the bottom of PCA plates. Sexual morph not observed.
Culture characteristics: After 7 d cultures on SNA flat, rhizoid, aerial mycelium is fine felty, grey olivaceous, colonies colourless, pale olivaceous grey coloured by aerial conidia, black hyphal plaques at the bottom of the plate, colonies reaching 42 mm diam; cultures on PCA flat, entire, aerial mycelium is floccose, pale olivaceous grey, colonies colourless with grey olivaceous rings, centre olivaceous, black hyphal plaques at the bottom of the plate; colonies reaching 46 mm diam.
Specimen examined: New Zealand, from Chrysanthemum sp., before May 1973, K.S. Milne (holotype CBS H-23045, culture ex-type CBS 117255 = E.G.S. 31.008).
Notes: Characteristic for the new species S. chrysanthemicola are the hyphal plaques which are formed at the bottom of the agar plates. These hyphal plaques are also observed in S. novae-zelandiae but after 14 d on PCA only.
Stemphylium drummondii Nirenberg & Plate, Phytopathol. Z. 107: 365. 1983.
Synonyms: Pleospora drummondii Nirenberg & Plate, Phytopathol. Z. 107: 365. 1983.
Stemphylium spinaciae B.J. Li, Yan F. Zhou & Y.L. Guo, Mycosystema 30: 380. 2011.
Notes: Comparison of the ITS (HQ622100) and gapdh (JF489118) sequence of the type of S. spinaciae (Zhou et al. 2011) with the type of S. drummondii showed identical ITS sequences and nearly identical gapdh sequences (1 nt difference in 374 nt). Together with the matching spore size (S. spinaciae 20–40 × 17.5–25 μm, S. drummondii 33.8 × 22.6 μm), we propose to synonymise these species. The description of a smooth conidial wall in S. spinaciae, which is incongruent with the verrucose conidia in S. drummondii, is questioned, since in fig. 1D of the original description (Zhou et al. 2011) verrucose conidia can be seen.
Stemphylium eturmiunum E.G. Simmons, Harvard Pap. Bot. 6: 204. 2001.
Synonyms: Pleospora eturmiuna E.G. Simmons, Harvard Pap. Bot. 6: 206. 2001.
Stemphylium variabilis Yong Wang bis & X.G. Zhang, Mycologia 102: 711. 2010.
Stemphylium capsici Yong Wang bis & X.G. Zhang, Mycotaxon 96: 80. 2006.
Specimens examined: China, Yunnan Province, Dali, from Capsicum annuum leaves, 5 Aug. 2002, X.G. Zhang (culture ex-type of S. capsici CBS 138495 = E.G.S. 53.123). France, Angres, from Allium sativum leaves, Aug. 2006, X.G. Zhang (culture ex-type of S. variabilis CBS 122641). New Zealand, Levin, from Solanum lycopersicum fruit, 1969, G.F. Laundon (culture ex-type of P. eturmiuna CBS 109845 = E.G.S. 29.099).
Notes: Morphological examination supports the synonymy of S. capsici and S. variabilis under S. eturmiunum (Fig. 6). Stemphylium capsici was described based on morphology only (Wang & Zhang 2006). Although the description of S. capsici describes smooth-walled conidia, our morphological examination of the ex-type isolate (CBS 138495) clearly shows densely verrucose conidia (Fig. 6B). Stemphylium variabilis was described based on morphological characters and molecular phylogenetic analyses (Wang et al. 2010). However, some sequence differences between the published sequences of S. variabilis (ITS GQ395366, gapdh GQ395373) and our sequences (ITS KU850543, gapdh KU850691, 3 and 4 nt difference respectively) placed S. variabilis in synonymy with S. eturmiunum instead of the close phylogenetic relationship published originally. Morphologically the variable shape of conidia and abundant secondary conidiophores were mentioned as being unique for S. variabilis, and different from the broadly ovoid or ellipsoid conidia of S. eturmiunum (Wang et al. 2010). However, our morphological examination did not show extensive secondary conidiophore formation or highly variable shaped conidia in the type isolate of S. variabilis (CBS 122641, Fig. 6C).
Fig. 6.
Stemphylium eturmiunum conidiophores and conidia. A. CBS 109845. B. CBS 138495. C. CBS 122641. Scale bars = 10 μm.
Stemphylium gracilariae E.G. Simmons, Mem. New York Bot. Gard. 49: 305. 1989.
Synonyms: Pleospora herbarum f. lactucum Padhi & Snyder, Phytopath. 44: 179. 1954. (nom. inval.)
Pleospora gracilariae E.G. Simmons & S. Schatz, Mem. New York Bot. Gard. 49: 305. 1989.
Stemphylium cucumis Y.F. Pei & X.G. Zhang, Mycol. Progr. 10: 167. 2011.
Specimens examined: China, Sinkiang province, Korla, from Cucumis melo leaves, collection date unknown, Y.F. Pei (culture ex-type of S. cucumis CBS 125060). Israel, from Gracilaria sp., collection date unknown, S. Schatz (culture ex-type of S. gracilariae CBS 482.90 = E.G.S. 37.073). Spain, Tenerife, from Leucospermum sp. (Rigoletto), 1 Apr. 2000, S. Denman, CBS 115179; Tenerife, from Leucospermum sp. (Succession), 1 Apr. 2000, S. Denman, CBS 115180. USA, California, from Solanum lycopersicum fruit, collection date unknown, G.B. Ramsey, CBS 308.36 = ATCC 10737. Unknown, from leaf of Lactuca sp., collection date unknown, W.C. Snyder (culture ex-type P. herbarum f. lactucum CBS 273.55).
Notes: In this study CBS 273.55 is recognised as ex-type culture of Pleospora herbarum f. lactucum based on the study of the original data deposited in the CBS culture collection archive. This correspondence showed that the isolate was deposited in the collection by the original author of the species (W.C. Snyder), after a request from the curator of the CBS collection to deposit the new species. Therefore P. herbarum f. lactucum will be synonymised with S. gracilariae instead of P. herbarum under which name it is currently synonymised. The description of S. cucumis was based on morphology and molecular phylogenetic analyses (Pei et al. 2011). Although their phylogenetic tree places S. cucumis distant from S. gracilariae, their sequences published for S. gracilariae and S. cucumis are identical (S. cucumis GU182942, GU182939, S. gracilariae AF442784, AF443883, for ITS and gapdh respectively). In the tree, S. cucumis was probably exchanged with S. luffae which is placed in close phylogenetic relation with S. gracilariae in the tree. However, sequence comparisons between the ex-type isolate of S. luffae and S. gracilariae show multiple nucleotide differences. The morphological description of S. cucumis also fits the description of S. gracilariae and is therefore synonymised here. Culture CBS 308.36, isolated from tomato in California, USA, was stored as Pleospora lycopersici in the CBS collection. However, the original description of P. lycopersici was from Solanum lycopersicum in Belgium (Marchal & Marchal 1921). Therefore, based on this single strain, we choose not to synonymise P. lycopersici with S. gracilariae at this point pending the collection of more isolates.
Stemphylium halophilum (J. Webster) Woudenb. & Crous, comb. nov. MycoBank MB820660.
Basionym: Pleospora halophila J. Webster, in Subramanian, Taxonomy of Fungi, (Proc. Int. Symp. Madras 1973) Part 2 (Madras): 349. 1984.
Specimens examined: UK, England, Devon, Exeter, Dawlish Warren, from Limonium vulgare, coll. date unknown, J. Webster (holotype HME 3143, culture ex-type CBS 337.73); England, Devon, near Exeter, from Armeria maritima, 10 Aug. 1972, J. Webster, CBS 410.73.
Note: The transfer of P. halophila to the genus Stemphylium is in congruence with an earlier study based on the large subunit 28S nr DNA (Kodsueb et al. 2006).
Stemphylium lancipes (Ellis & Everh.) E.G. Simmons, Mycologia 61: 21. 1969.
Basionym: Alternaria lancipes Ellis & Everh., J. Mycol. 4: 45. 1888.
Specimens examined: New Zealand, from Aquilegia sp., collection date and collector unknown, CBS 116584 = E.G.S. 46.182; from Aquilegia sp., Jul. 1998, HM Dance, CBS 101217. USA, Kansas, from Aquilegia canadensis, collection date and collector unknown (epitype designated here CBS H-23043, MBT375502, culture ex-epitype CBS 133314 = E.G.S. 10.022).
Notes: The type material from Alternaria lancipes, basionym of Stemphylium lancipes, was originally described from Argemone sp. collected in Manhattan, Kansas, USA (Ellis & Everhart 1888). The holotype material, stored at the NY herbarium (ID 00830044), was studied by Emory G. Simmons, who subsequently transferred the species to the genus Stemphylium (Simmons 1969). However, two other collections from the same locality are on Aquilegia sp., which yielded the isolate Emory G. Simmons studied (Simmons 1969). Here we propose this isolate (CBS 133314), isolated from Aquilegia canadensis in Kansas, USA, as epitype of A. lancipes.
Stemphylium lucomagnoense Woudenb. & Crous, sp. nov. MycoBank MB820661. Fig. 7.
Fig. 7.
Stemphylium lucomagnoense sp. nov. (CBS 116601). A–C. Conidiophores and conidia. D. Ascoma. E. Ascomatal wall. Scale bars: A–C, E = 10 μm; D = 100 μm.
Etymology: Named after the place of isolation, Lucomagno, the Lukmanier Pass in Switzerland.
On PCA after 14 d: Conidiophores solitary, straight to flexuous, occasionally branched, septate, smooth, sub-hyaline, (34–)46–95(–119) × (2.5–)3–4(–4.5) μm, bearing multiple darkened percurrent rejuvenation sites. Conidiogenous cells swollen at the apex, darkened, (4–)5–6.5(–7.5) μm wide. Conidia solitary or in short chains of 2 conidia, conidium body is dark brown, inconspicuously verrucose, ellipsoid to broad ovoid, (18.5–)20–27(–31) × (9.5–)11–16(–18) μm, L/W = 1.8, with (2–)3 transverse septa and 1–2 longitudinal or oblique septa per transverse sector. Constricted at 1–3 darkened transverse septa. Immature ascomata of sexual morph observed in agar, pseudothecia globose or broad ovoid, single, covered with dark hyphal outgrows, ranging in size to 485 μm tall.
Culture characteristics: After 7 d cultures on SNA flat, rhizoid, aerial mycelium is scarce, colonies colourless, no sporulation, colonies 5 mm diam; cultures after 7 d on PCA flat, entire, aerial mycelium woolly, pale olivaceous grey, colonies greenish olivaceous with two olivaceous rings, young colourless ascomata in agar which become black after 14 d, colonies reaching 28–30 mm diam.
Specimen examined: Switzerland, Ticino, Lucomagno, from Minuartia hybrida, 19 Jun. 1981, P.G. Crivelli (holotype CBS H-23046, culture ex-type CBS 116601 = E.G.S. 37.017).
Notes: Culture CBS 116601 was deposited as Pleospora gigaspora in the CBS collection, as diagnosed by Crivelli (Inderbitzin et al. 2009). Pleospora gigaspora was originally described from dead shoots of “herbarum majorum” from the inlands of “Maris glacialis, Kildin”, Russia (Karsten 1884), with smooth ascomata of 300–400 μm and no description of the asexual morph. Since our species has dark hyphal outgrows on its ascomata and is obviously different, we provided this species with a new name. Pleospora minuartiae is described from dry leaves of Minuartia taurica from Mt. Babugan-Yayla, Tauria, Crimea, Ukraine (Gucevicz 1972). This species is described with small ascomata measuring 140–180 μm, which significantly differs from our species for which ascomata of up to 485 μm tall are observed. Since there is also a morphologically different Pleospora species named after the country of isolation, P. helvetica with small ascomata measuring 180–200 μm (Niessl 1867), we named our isolate after the place of isolation, Lucomagno, the Lukmanier Pass.
Stemphylium lycopersici (Enjoji) W. Yamam., Trans. Mycol. Soc. Japan 2: 93. 1960. Fig. 8.
Fig. 8.
Stemphylium lycopersici conidiophores and conidia after 7 d on PCA. A–B. CBS 122639. C. CBS 120325. D. CBS 122803. E–F. CBS 124981. G. CBS 124980. Scale bars = 10 μm.
Basionym: Thyrospora lycopersici Enjoji, J. Pl. Protect. 18: 52. 1931.
Synonyms: Stemphylium xanthosomatis B. Huguenin, as “xanthosomae”, Bull. Soc. Mycol. France 81: 697. 1966.
Stemphylium plantaginis Yong Wang bis & X.G. Zhang, Mycotaxon 96: 79. 2006.
Stemphylium pruni Yong Wang bis & X.G. Zhang, Mycotaxon 96: 78. 2006.
Stemphylium oblongum Yong Wang bis & X.G. Zhang, Nova Hedwigia 88: 201. 2009.
Stemphylium pyrina Yong Wang bis & X.G. Zhang, Mycol. Progr. 8: 303. 2009.
Stemphylium sophorae Yong Wang bis & X.G. Zhang, Nova Hedwigia 88: 200. 2009.
Stemphylium platycodontis J.X. Deng & S.H. Yu, Mycol. Progr. 13: 479. 2014.
Specimens examined: China, Guizhou Province, Guiyang, from Solanum lycopersicum leaves, collection date unknown, Y. Wang (neotype designated here of T. lycopersici CBS H-23051, MBT375506, culture ex-neotype CBS 122639); Guizhou Province, Guiyang, from Prunus persica leaves, 16 Aug. 2003, Y. Wang (culture ex-type of S. pruni CBS 124980); Shandong Province, Taian, from Gossypium hirsutum leaves, 3 Oct. 2004, X.G. Zhang (culture ex-type of S. oblongum CBS 120326); Shandong Province, Mountain Tai, from Plantago major leaves, 5 Oct. 2003, Y. Wang (culture ex-type of S. plantaginis CBS 124981); Shandong Province, Mountain Tai, from Sophora microphylla leaves, 3 Oct. 2004, Y. Wang (culture ex-type of S. sophorae CBS 120325); Sinkiang Province, Korla, from Pyrus sinkiangensis leaves, 9 Aug. 2006, Y. Wang (culture ex-type of S. pyrina CBS 122803). New Caledonia, Nouméa, from Xanthosoma sagittifolium, 1962, B. Huguenin (culture ex-type of S. xanthosomatis CBS 116585 = E.G.S. 17.137 = IMI 98083).
Notes: Stemphylium lycopersici, with Thyrospora lycopersici as basionym, was originally described from Solanum lycopersicum in Japan, but lacks a holotype specimen (Enjoji 1931). The culture CBS 116587, isolated from Solanum lycopersicum in the Dominican Republic, was considered by Emory G. Simmons to fit the concept of this species (Inderbitzin et al. 2009). Here we propose CBS 122639, isolated from Solanum lycopersicum in China, as ex-neotype of T. lycopersici, since this isolate is from a geographically closer location, and also clusters in the same phylogenetic species clade. The type-isolate of S. platycodontis (CNU 111092) is not included in this study, but another one is included, namely CBS 333.73, also isolated from Platycodon sp. and regarded as S. platycodontis (Deng et al. 2014). Stemphylium platycodontis was described based on phylogenetic study of the ITS, gapdh and tef1 partial gene sequences in combination with morphology studies. When comparing the ITS, gapdh and cmdA sequence of isolate CBS 333.73, only the gapdh sequence is unique for the two isolates from Platycodon, with only 1 nt difference. Together with the minor morphological differences described, slightly larger spore size (S. platycodontis 33–80 × 12–22, S. lycopersici 21–60 × 12–24 μm) and no production of brown pigment in PDA of S. platycodontis, we propose to synonymise S. platycodontis under S. lycopersici. Five synonymised species under S. lycopersici were described based on morphology alone. Stemphylium oblongum, S. plantaginis, S. pruni, S. pyrina and S. sophorae were described as new species from China (Wang and Zhang, 2006, Wang et al., 2009, Wang and Zhang, 2009), with some even appearing in the same manuscript. However, the broad conidial size range (21–60 × 12–24 μm) and described shape of conidia (ellipsoidal, ovoid, short cylindrical or shortly obclavate) of S. lycopersici by Yamamoto (1960), results in the fact that all described species fit the concept of S. lycopersici. The only difference in the descriptions is the structure of the conidial wall. This ranges from smooth (S. plantaginis and S. pruni) to densely tuberculate (S. pyrina) including descriptions with both smooth and finely postulate/micromaculate conidia (S. oblongum and S. sophorae). The description of Stemphylium lycopersici mentions echinulate (with sharply pointed spines) conidia. Morphological examination showed that all studied isolates have roughened conidia (Fig. 8), including the ex-type isolates of S. plantaginis (CBS 124981, Fig. 8E–F) and S. pruni (CBS 124980, Fig. 8G).
Stemphylium subglobuliferum was described based on a phylogenetic study of the ITS and gapdh partial gene sequences in combination with morphological studies (Xue et al. 2005). The ITS sequence of S. subglobuliferum (AY751454) is 100 % identical with S. lycopersici, and the gapdh sequence (AY751459) only has 1 unique nt compared to our S. lycopersici gapdh sequences. However, S. subglobuliferum was described as a new species based on the smaller spore size (9–20 × 5–13) and smooth conidial wall. A re-examination of the type-isolate is needed to clarify if this is indeed another synonym of S. lycopersici.
Based on our specimens examined, Stemphylium lycopersici has a broad host range infecting plant leaves from at least six different families (Araceae, Fabaceae, Malvaceae, Plantaginaceae, Rosaceae and Solanaceae).
Stemphylium novae-zelandiae Woudenb. & Crous, sp. nov. MycoBank MB820662. Fig. 9.
Fig. 9.
Stemphylium novae-zelandiae sp. nov. (CBS 138295). A, D. Conidiophores and conidia. B–C. Conidia. E. Hyphal plaques. Scale bars = 10 μm.
Etymology: Named after the country where it was isolated, New Zealand.
Conidiophores solitary, straight to flexuous, unbranched, septate, smooth, sub-hyaline, (46.5–)64.5–111(–144.5) × (2.5–)3–4.5(–5.5) μm, bearing 1–2 thickened percurrent rejuvenation sites. Conidiogenous cells swollen at the apex, darkened, (5–)6–7.5(–8.5) μm wide. Conidia solitary, conidium body is light olive brown, verrucose, cylindrical, (31–)34–40.5(–45.5) × (9–)11–13(–14.5) μm, L/W = 3.1, with 3–5(–7) transverse septa and 1–2 longitudinal or oblique septa per transverse sector. Constricted at 2–3 darkened transverse septa. Forms hyphal plaques at the bottom of PCA plates after 14 d. Sexual morph not observed.
Culture characteristics: After 7 d cultures on SNA flat, entire, aerial mycelium is scarce, wooly, white, colonies colourless, with three pale olivaceous grey rings and centre, colonies 20–24 mm diam; cultures after 7 d on PCA flat, entire, aerial mycelium fine felty, pale olivaceous grey, colonies white to olivaceous buff with two grey olivaceous rings and a greenish olivaceous outer ring, colonies reaching 35 mm diam.
Specimens examined: New Zealand, Waitakaruru, from dead leaf of Avicennia resinifera, 10 Sep. 2006, C.F. Hill (holotype CBS H-23047, culture ex-type CBS 138295 = E.G.S. 52.148 (06/5200B)); additional strain from the same source CBS 138157 = E.G.S. 52.147 (06/5200A).
Notes: To avoid confusion with the species Pleospora avicenniae (Borse 1987), we named the species after the country where it was isolated, New Zealand, instead of the host of isolation. Recently Pleospora avicenniae was placed in the new genus Halojulella based on a morphological and molecular examination (Ariyawansa et al. 2013). As in S. chrysanthemicola, S. novae-zelandiae forms hyphal plaques at the bottom of the PCA plate but these are only observed after 14 d.
Stemphylium simmonsii Woudenb. & Crous, sp. nov. MycoBank MB820663. Fig. 10.
Fig. 10.
Stemphylium simmonsii sp. nov. (CBS 133518). A–C. Conidiophores and conidia. D. Conidia. E. Ascomata. Scale bars: A–D = 10 μm; E = 100 μm.
Etymology: Named after Emory G. Simmons, who extensively studied Pleospora and Stemphylium species.
Conidiophores solitary, straight to flexuous, occasionally branched, septate, smooth, sub-hyaline, (18–)30–93(–159) × (2–)3–4(–5) μm, bearing multiple darkened percurrent rejuvenation sites. Conidiogenous cells swollen at the apex, darkened, (4.5–)5–6.5(–7.5) μm wide. Conidia solitary, conidium body is pale olive brown, verrucose, ellipsoid to broad ovoid, (18–)20.5–24.5(–28) × (11–)13–16(–18.5) μm, L/W = 1.6, with (2–)3 transverse septa and (1–)2(–3) longitudinal or oblique septa per transverse sector. Often constricted at the middle, darkened transverse septum. Immature ascomata of sexual morph observed in and on agar, pseudothecia subglobose or broad ovoid, single, covered with dark hyphal outgrows, ranging from 175 to 365 μm tall.
Culture characteristics: After 7 d cultures on SNA flat, rhizoid, aerial mycelium is fine felty, pale olivaceous grey, colonies colourless, pale olivaceous grey coloured by aerial conidia in rhizoid shape, colonies 45–55 mm diam; cultures on PCA flat, entire, aerial mycelium scarce, woolly, pale olivaceous grey, colonies colourless with three grey olivaceous rings, and centre olivaceous to iron-grey with ascomata in and on agar, colonies reaching 60 mm diam.
Specimens examined: Australia, from Malus sylvestris fruit, 1 Apr. 1976, C. Robertson, CBS 134496 = E.G.S. 42.138. Canada, from Fragaria sp., before 1971, C.O. Gourlay (holotype CBS H-23048, culture ex-type CBS 133518 = E.G.S. 30.154); from Solanum lycopersicum leaf, before 1971, C.O. Gourlay, CBS 133515 = E.G.S. 30.153; British Colombia, Ladner, from Phragmites sp. leaves, 7 Feb. 1999, A. & R. Bandoni & S. landvik & P. Inderbitzin, CBS 116598 = UAMH 104876; British Colombia, Sidney, from Lactuca muralis, 22 May 2001, M.E. Barr, CBS 116603; British Colombia, Sidney, from Geum macrophyllum, 22 May 2001, M.E. Barr, CBS 116604. USA, Maryland, Laurel, from Commelina sp. leaf, 14 Aug. 1966, E.G. Simmons, CBS 716.68. = E.G.S. 17.151 = ATCC 18518 = IMI 135458 = MUCL 11718; Massachusetts, Hadley, from Trifolium pratense leaf, 20 Jun. 1985, E.G. Simmons, CBS 133894 = E.G.S. 38.115.
Notes: Three examined isolates were named S. globuliferum by E.G. Simmons (CBS 716.68, CBS 133894, CBS 134496). Since the original description of M. globuliferum was from Lotus corniculatus (Fabaceae) from Gotland, Sweden (Vestergren 1896), we did not follow this identification but introduced the new name S. simmonsii. Morphologically S. simmonsii resembles S. botryosum, which is phylogenetically only distantly related. Phylogenetically it is closely related to S. beticola, which can easily be distinguished from S. simmonsii by its glabrous ascomata (Fig. 3D–E; S. simmonsii has ascomata with dark hyphal outgrows, Fig. 10E). See the general discussion below for additional information.
Stemphylium solani G.F. Weber, Phytopathol. 20: 516. 1930.
Synonym: Thyrospora solani (G.F. Weber) Sawada, Rep. Dept. Agric. Gov. Res. Inst. Formosa 51: 115. 1931.
Specimens examined: USA, Indiana, Darlington, from Solanum lycopersicum, Sep. 1993, E.G. Simmons (epitype designated here CBS H-23049, MBT375504, culture ex-epitype CBS 116586 = E.G.S. 41.135); Kansas, Riley County, from Euphorbia marginata leaf, 6 Nov. 1994, D. Stuterille, CBS 118082 = E.G.S. 42.055; South Carolina, Charleston, from Solanum lycopersicum, 1952, C.F. Andrus, CBS 408.54 = ATCC 11128.
Notes: Stemphylium solani was originally described from diseased tomato plants collected in Florida, USA (Weber 1930). The holotype material is stored in the Florida Agricultural Experiment Station Herbarium, now named University of Florida Herbarium, under the specimen number FLAS-F-13571. According to Emory G. Simmons, CBS 116586, isolated from Solanum lycopersicum from Indiana, USA, was a good representative of the species after examination of the type material (Inderbitzin et al. 2009). We follow his suggestion and designate CBS 116586 as ex-epitype culture of S. solani.
Stemphylium vesicarium (Wallr.) E.G. Simmons, Mycologia 61: 9. 1969. Fig. 11.
Fig. 11.
Stemphylium vesicarium. A–D. (CPC 29939). Asci, pseudoparaphyses, and ascospores. E–I. (CBS 123005). Conidiophores and conidia. Scale bars = 10 μm.
Basionym: Helminthosporium vesicarium Wallr. [as ‘Helmisporium’], Fl. Cryptog. German. 2: 166. 1833.
Synonyms: Macrosporium vesicarium (Wallr.) Sacc., Syll. Fungorum 4: 537. 1886.
Sphaeria herbarum Pers.: Fr, Syn. Meth. Fungorum 1: 78. 1801.
Pleospora herbarum (Pers.: Fr) Rabenh. ex Ces. & De Not.: Fr Comment. Soc. Crittog. Ital. 1:217. 1863.
Pleospora pomorum A.S. Horne, J. Bot. 58: 239. 1920.
Stemphylium herbarum E.G. Simmons, Sydowia 38: 291. 1986.
Pleospora alfalfae E.G. Simmons, Sydowia 38: 292. 1986.
Stemphylium alfalfae E.G. Simmons, Sydowia 38: 292. 1986.
Pleospora sedicola E.G. Simmons, Harvard Pap. Bot. 6: 202. 2001.
Stemphylium sedicola E.G. Simmons, Harvard Pap. Bot. 6: 202. 2001.
Pleospora tomatonis E.G. Simmons, Harvard Pap. Bot. 6: 204. 2001.
Stemphylium tomatonis E.G. Simmons, Harvard Pap. Bot. 6: 204. 2001.
Stemphylium cremanthodii Y.F. Pei & X.G. Zhang, Mycotaxon 109: 494. 2009.
Stemphylium mali Yong Wang bis & X.G. Zhang, Mycol. Progr. 8: 303. 2009.
Stemphylium brassicicola Y.F. Pei & X.G. Zhang, Mycotaxon 111: 169. 2010.
See Index Fungorum for additional synonyms.
Specimens examined: Australia, Western Australia, Harvey, from Medicago sativa, 30 Jul. 1982, collector unknown (culture ex-type of P. alfalfae CBS 192.86 = E.G.S. 36.088 = IMI 269683). China, Sinkiang province, Korla, from Cremanthodium discoideum leaves, 16 Oct. 2008, Y.F. Pei (culture ex-type of S. cremanthodii CBS 124747); Sinkiang province, Korla, from Brassica pekinensis leaves, 7 Aug. 2009, Y.F. Pei (culture ex-type of S. brassicicola CBS 124749); Sinkiang Province, Yili, from Malus sieversii leaves, 19 Jul. 2005, Y. Wang (culture ex-type of S. mali CBS 122640). India, Uttar Pradesh, Jhansi, from Medicago sativa, 1983, H.K. Joshi (culture ex-type of S. herbarum CBS 191.86 = E.G.S. 36.138 = IMI 276975). New Zealand, Auckland, from Sedum spectabile leaf lesion, Mar. 2000, E.G. Simmons (culture ex-type of P. sedicola CBS 109843 = E.G.S. 48.095 = IMI 386967). UK, England, from Malus domestica fruit, collection date unknown, M.N. Kidd (neotype of P. pomorum designated here CBS H-23044, MBT375503, culture ex-neotype CBS 184.25). USA, California, Central Valley, from Solanum lycopersicum fruit, Oct. 1968, E.G. Simmons (culture ex-type of P. tomatonis CBS 109844 = E.G.S. 29.089 = IMI 386968).
Notes: Pleospora pomorum was originally described from spotted apples in Britain, without the designation of a holotype specimen (Horne 1920). A second publication on the species was done by Kidd & Beaumont (1924), who deposited isolate CBS 184.25, from apple fruit in England in the CBS collection. Since no holotype specimen is known, we propose CBS 184.25 as ex-neotype culture of Pleospora pomorum. Therefore, P. pomorum will be synonymised with S. vesicarium. The first molecular study of Stemphylium species showed that S. alfalfae, S. herbarum, and S. vesicarium were identical based on their ITS and gapdh sequences (Câmara et al. 2002). A more extensive phylogenetic analysis on DNA sequences from four loci ITS, gapdh, tef1 and the intergenic spacer between vmaA and vpsA (Inderbitzin et al. 2009) showed the same clustering, and added the species P. sedicola and P. tomatonis to the species clade. However, small morphological differences have been used to distinguish among the species now synonymised under S. vesicarium (summarised in Table 3). Although the described differences seem sometimes considerable, they are not always obvious when performing morphological studies (illustrated by pictures 1–5 in fig. 4 of Inderbitzin et al. 2009). See the general discussion below for additional information on the synonymies proposed here for S. vesicarium. Only the synonyms of S. vesicarium proposed in this research are listed, for the full list of synonyms see Index Fungorum (http://www.indexfungorum.org).
Table 3.
Conidial characteristics of Stemphylium species synonymised under S. vesicarium.
| Species | Conidial shape | Conidial size (μm) | L/B ratio1 | Transverse septa | Longitudinal septa | Wall ornamentation | Reference |
|---|---|---|---|---|---|---|---|
| S. alfalfae | Oblong | 30–40(–45) × 12–15(–18) | ND | 6–7 | 1–2 | Minutely verrucose | Simmons (1985) |
| Spherical or ovoid | 32–35 × 16–19 | ND | 3–4 | variable | Minutely verrucose | Simmons (1985) | |
| S. brassicicola | Subdoliiform, cylindrical to oblong cylindrical | 32–45 × 12–19 | 2–3.1 | 1–4(–5) | 3–5(–6) | Conspicuously punctulate to punctate | Pei et al. (2010) |
| S. cremathodii | Oblong to oblong-ellipsoid | 18–31 × 9–19 | 1.5–2.6 | 1–3 | 0–3 | Micromaculate | Pei et al. (2009) |
| S. herbarum | Broadly ovoid or broadly ellipsoid, sometimes inequilateral | 35–45 × 20–27 | ND | 6–7 | 1–3 | Conspicuously and densely verrucose | Simmons (1985) |
| S. mali | Oblong | 18–22 × 13–16 | 1.3–1.6 | 1–3 | 3–5 | Conspicuoulsy punctate | Wang et al. (2009) |
| Subspherical | 14–16.5 (diam) | ND | 1(–3) | 2–4 | Conspicuoulsy punctate | Wang et al. (2009) | |
| S. sedicola | Broadly ellipsoid or oblong | 30–35 × 18–20 | ND | 2–3 | 1–3 | Smooth or usually punctate | Simmons (2001) |
| S. tomatonis | Oblong, broadly ellipsoid (or subglobose) | 46–48 × 13–16 | 2.4–3 (or 1–1.5) | 4–7 | 1–2 | Punctulate | Simmons (2001) |
| S. vesicarium | Oblong or broadly oval, sometimes inequilateral | 25–42(–48) × 12–22 | 1.5–2.7 | 1–5(–6) | 1–2(–3) | Conspicuously and densely verrucose | Simmons (1969) |
ND: not determined.
Discussion
This manuscript presents a molecular phylogenetic overview of species in the genus Stemphylium known from culture, initiated due to our inability to unequivocally identify a Stemphylium sp. causing yellow leaf spot in sugar beet. To be able to characterise the species, all currently known (and available) species of the genus had to be considered. However, the lack of (ex-)type material often makes it difficult to determine species names of fungi, described on morphology only, onto the modern DNA-based phylogenetic trees. To strengthen and stabilise the taxonomy of Stemphylium, three epitypes, one lectotype and two neotypes are proposed in the present study. However, some isolates represent names for which no ex-type isolate is present or for which it was difficult to designate an appropriate ex-epitype culture (highlighted with bold species names in Fig. 1).
Seven isolates were named Stemphylium globuliferum by Emory G. Simmons based on morphology. Stemphylium globuliferum was originally described as Macrosporium globuliferum from Lotus corniculatus (Fabaceae) from Gotland, Sweden (Vestergren 1896). Emory G. Simmons studied the holotype material (in UPS) and placed this species in Stemphylium (Simmons 1969). He described it as a common species, and isolated it from Trifolium pratense (Fabaceae). Four of the included isolates fall within the S. botryosum clade, and three within Stemphylium simmonsii sp. nov. Since none of these isolates originate from Lotus corniculatus, or are from Sweden (or even Europe), we choose not to use the name Stemphylium globuliferum for the new species, but rather provide it with a new name (S. simmonsii sp. nov.).
Stemphylium vesicarium, with Helminthosporium vesicarium as basionym, was originally described from Allium sativum in Germany (Wallroth 1833). Our dataset includes 25 isolates named S. vesicarium of which 20 were named, based on morphology, by Emory G. Simmons, who also studied the holotype specimen at STR. One isolate, not studied by him, clusters with S. lycopersici (CBS 436.76), two isolates (one identified by him) cluster with S. eturmiunum, and the other 22 all cluster within the Stemphylium vesicarium clade (based on ITS, Fig. 1). Since none of the isolates originate from Allium sativum in Germany (or from a geographically close location), no ex-epitype culture is proposed for the species.
As already mentioned in the introduction, the Pleospora herbarum clade sensu Inderbitzin et al. (2009) illustrated the problems with identification in the genus Stemphylium. Molecular studies demonstrated the phylogenetic identity of the species S. alfalfae, S. herbarum, S. sedicola, S. tomatonis, and S. vesicarium (e.g. Câmara et al., 2002, Inderbitzin et al., 2009). However, differences in RAPD fingerprints (Chaisrisook et al. 1995) and morphology (Simmons, 1969, Simmons, 1985, Simmons, 1989, Simmons, 2001), seemed to support them to be separate species. It should be noted that the RAPD studies were only based on a small number of isolates, (including only two S. herbarum isolates and one S. vesicarium isolate) and morphologically only small differences have been used to make a distinction among these species although they also share many characters (Câmara et al. 2002, table 2 of Kurose et al. 2015). As a result, some researchers chose to retain all the species names (e.g. Inderbitzin et al. 2009), while others chose to synonymise them (e.g. Köhl et al. 2009, as S. vesicarium). To be able to construct a stable phylogenetic species concept in Stemphylium we proposed to synonymise these phylogenetically identical species under S. vesicarium. The conidial descriptions of the species now synonymised under S. vesicarium are summarised in Table 3.
The species S. sarciniforme (Fig. 2, clade 19) is divided in two well-supported subclades. Five isolates from Trifolium pratense form one branch, and three isolates from Cicer arietinum, Iran, all isolated by W. J. Kaiser, form a separate branch. Isolate CBS 110049, from the Cicer arietinum clade, was submitted to the CBS collection in 2002 as ex-holotype of “S. kaiseri”, but this name was never published. Emory Simmons morphologically identified all isolates from this clade as S. sarciniforme, and also chemically the isolates from both clades are similar (B. Andersen, pers. comm.). Until more isolates become available, we choose to treat them here as S. sarciniforme.
After revision of the species identity and names, 28 species can be distinguished in the genus Stemphylium based on (parts) of the ITS, gapdh and cmdA gene regions (Fig. 2). From these 28 species, five new species are described, two new name combinations are introduced and 22 names are synonymised. Of the 22 synonymised names, seven are placed in synonymy with S. lycopersici, seven with S. vesicarium, three with S. amaranthi, two with S. gracilariae and S. eturmiunum, and one with S. drummondii. Stemphylium subglobuliferum might also be a synonym of S. lycopersici (see notes of S. lycopersici). The majority of the synonymised species (16 out of 22) were described from China based mostly on morphology and host-specificity. Clearly in the genus Stemphylium, identification on morphology and host-specificity alone is insufficient for correct species identification. Several other “new” species are described from China based solely on morphology, e.g S. allii-cepae, S. basellae, S. descurainiae, S. gossypii, S. hydrangeae, S. lactucae, S. momordicae, S. pisi and S. turriforme (Zhang and Zhang, 2002, Zhang et al., 2003, Zhang and Zhang, 2007, Zhou et al., 2012). Until molecular data of the ex-type isolates become available, the status of these species names remains unclear.
Based only on ITS sequences, 22 species can be identified to species level (Fig. 1). Only four clades (clade 1, 7, 10, and 22), containing in total 10 species names, have multiple species names associated with them. This means that for accurate species identification, an additional gene to the standard ITS barcode sequence is required in the case of these 10 species. This study will therefore be useful to other plant pathologists in the field trying to identify their Stemphylium species, not only by providing them with the correct name(s), but also in helping them choose appropriate loci that will ensure correct identification.
Conclusions
In the genus Stemphylium 28 species can be distinguished based on (parts) of the ITS, gapdh and cmdA gene regions. From these 28 species, five are described as new species and a further two new combinations are proposed. Twenty-two names are reduced to synonymy. To create a stable taxonomy for Stemphylium, three epitypes, one lectotype and two neotypes are designated. Morphological examination alone is not suited for species identification in Stemphylium. For an accurate species identification, morphological studies should be combined with molecular data.
Acknowledgements
We would like to thank Carmen Wijnen (Westerdijk Institute, Evolutionary Phytopathology group) for help with DNA isolation and sequencing. The Netherlands Food and Consumer Product Safety Authority (NVWA) is acknowledged for financial support of the project.
Footnotes
Peer review under responsibility of Westerdijk Fungal Biodiversity Institute.
Supplementary data related to this article can be found at http://dx.doi.org/10.1016/j.simyco.2017.06.001.
Appendix A. Supplementary data
The following are the supplementary data related to this article:
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