Colletotrichum: complex species or species ... - CBS - KNAW

The Colletotrichum acutatum species complexNotes: The synonymy given for this species follows Farr et al.(2006), and this work should be consulted for details. Fusariumphormii was described by Hennings (1898) on leaves of Phormiumtenax in the Botanical Garden in Berlin, Germany, as formingsporodochia with oblong-cylindrical to fusoid, straight to slightlycurved, multiguttulate, hyaline conidia, measuring 18–25 × 4–6µm. Hennings (1898) found this fungus together with Physalosporaphormii, and assumed the two belonged together. Fusarium phormiiis formed on the leaf surface, while the perithecia of P. phormiiappear on the undersurface. Kinghorn (1936) observed structuresconsidered to be the sexual morph of C. phormii on leaves ofPhormium plants but not in culture, as did von Arx (in litt.). We havefound, however, that Kinghorn was looking at two species; partof this material belongs to a species that is named in the presentpublication as C. kinghornii. The sexual morph, originally namedas Physalospora phormii, was originally found by Schröter (1894)on dead leaves of Phormium tenax in Breslau, Germany (today:Wrocław, Poland).The sexual morph was not observed in our study. Farr etal. (2006) gave the following description: “Ascomata on upperand lower surface of leaves in large, elliptical, discoloured areassimilar to those bearing acervuli, with or without a narrow, blackmargin, subepidermal, sometimes partially erumpent, solitary,scattered to crowded or aggregated, black, shiny when exposed,globose to ellipsoid, flattened. Ascomatal walls of thin-walled,brown cells, 9–15 µm diam. Paraphyses sparse, inflated, hyaline.Asci unitunicate, narrowly clavate with a rounded apex and shortstipe, 56–70 × 15–20 µm, with an indistinct apical ring in immatureasci, 8-spored, obliquely seriate. Ascospores hyaline, non-septate,ellipsoidal, 15–22 × 4.5–6 µm.”Von Arx (1957) regarded Gloeosporium phormii as a synonymof C. gloeosporioides. However in the phylogeny of Farr et al.(2006), strains of this species cluster with C. acutatum and C. lupini.Morphological and cultural differences revealed C. phormii as adistinct lineage. We have confirmed this in our study. Colletotrichumphormii can be distinguished from the closely related C. salicis (andindeed from all other species in the C. acutatum complex) by itselongate, large conidia and large appressoria (Tables 2, 3). Thespecies appears to be host-specific to Phormium spp. Recently,Takeuchi & Hori (2006) reported C. gloeosporioides from Phormiumin Japan. However, based on dimensions of conidia (10–16.5 ×4–6 µm) and appressoria (7–17 × 4–11.5 µm) and the shape ofthe conidia – cylindrical with broadly rounded ends – (fig. 3 of thatpaper), the fungus seems to be a species in the C. gloeosporioidescomplex rather than one of the two C. acutatum complex membersfrom Phormium treated in this study.Colletotrichum phormii is separated from other species byTUB2, GAPDH, HIS3 and ACT sequences, and most effectivelywith HIS3. The CHS-1 sequence is the same as that of C. australe.The closest matches in a blastn search with the TUB2 sequence ofstrain CBS 118194 (with 99 % identity, 4 bp differences) was Ga.acutata isolate PCF 459 (EU635504) from strawberry in Belgium(Debode et al. 2009) and with 99 % identity (5 bp differences),isolate PT250 (= CBS 129953) AJ748624 from olive, Portugal(Talhinhas et al. 2005), which is here referred to C. rhombiforme.With the GAPDH sequence of strain CBS 118194 there was nomatch closer than 89 % identity. The closest matches in a blastnsearch with the ITS sequence with 100 % identity were the sameGenBank accessions as those obtained in blastn searches of C.salicis, C. pyricola and C. johnstonii.Colletotrichum pseudoacutatum Damm, P.F. Cannon &Crous, sp. nov. MycoBank MB800509. Fig. 24.Etymology: Named refers to the morphology that is similar to C.acutatum, which is not closely related.Sexual morph not observed. Asexual morph on SNA. Vegetativehyphae 1–5 µm diam, hyaline to pale brown, smooth-walled,septate, branched. Chlamydospores not observed. Conidiomataacervular, conidiophores and setae formed on a cushion of palebrown angular cells 3–8 µm diam. Setae rare (only one found),medium brown, smooth-walled, 2-septate, 57 µm long, basecylindrical, constricted at basal septum, 4 µm diam, tip somewhatround. Conidiophores hyaline to pale brown, smooth-walled,septate, branched, to 50 µm long. Conidiogenous cells hyaline,smooth-walled, cylindrical, often ± bent or partly inflated, 9–22 ×2–3.5 µm, opening 1 µm diam, collarette distinct, 0.5–1 µm long,periclinal thickening conspicuous. Conidia hyaline, smooth-walled,aseptate, straight, fusiform to cylindrical with both ends acute,(9.5–)11.5–13.5(–14.5) × 3.5–4 µm, mean ± SD = 12.7 ± 1.1 × 3.8± 0.2 µm, L/W ratio = 3.4. Appressoria in loose groups to denseclusters, pale brown, verruculose, irregular shape, (3–)5.5–18.5(–25) × (2.5–)3.5–7(–9.5) µm, mean ± SD = 12.0 ± 6.3 × 5.1 ± 1.7µm, L/W ratio = 2.3.Asexual morph on Anthriscus stem. Conidiomata acervular,conidiophores and setae formed on a cushion of pale brownangular cells 4–10 µm diam. Setae abundant, medium brown,basal cell often paler, smooth-walled, 65–130 µm long, mostly withone septum close to the base, (0–)1(–2)-septate, base cylindricalto conical, often ± bent, often looking like an outgrowth or likebeginning to branch, 3–5 µm wide, tip somewhat acute to slightlyroundish. Conidiophores hyaline, septate, branched, smoothwalled,to 30 µm long. Conidiogenous cells hyaline, smoothwalled,cylindrical to elongate ampulliform, 5.5–17 × 2.5–4(–5) µm,opening 1 µm diam, collarette distinct, 0.5–1 µm long, periclinalthickening visible, sometimes conspicuous. Conidia hyaline,smooth-walled, aseptate, straight, fusiform to cylindrical with bothends acute, (9.5–)11.5–13.5(–14.5) × 3.5–4 µm, mean ± SD = 15.0± 1.2 × 4.2 ± 0.3 µm, L/W ratio = 3.5.Culture characteristics: Colonies on SNA flat with undulate to lobatemargin, hyaline, pale honey in the centre, aerial mycelium lacking,filter paper grey and mottled, on Anthriscus stem partly coveredwith salmon to apricot acervuli; growth rate 13.5–17.5 mm in 7 d(23–26 mm in 10 d). Colonies on OA flat with undulate to lobatemargin; surface buff, sectors isabelline mottled and covered withsalmon to apricot acervuli, aerial mycelium lacking, reverse salmonand mottled olivaceous grey, centre iron-grey; growth rate 15–21mm in 13.5–21 mm in 7 d (21–27.5 mm in 10 d). Conidia in masssalmon to apricot.Material examined: Chile, Valdivia, San Patricio forest nursery of the CorporaciónNacional Forestal near San José de la Mariquina, from seedlings of Pinus radiata,between Dec 1976 and Feb 1977, unknown collector (isolated and deposited inCBS collection Aug. 1977 by H. Peredo López), (CBS H-20729 holotype, cultureex-holotype CBS 436.77).Notes: Peredo et al. (1979) reported a disease of Pinus radiataseedlings in a nursery in Chile. The seedlings bent leaders in asimilar manner to the “terminal crook” disease in New Zealand(Dingley & Gilmor 1972) and the affected part of the stem becamepinkish. The disease resulted in small seedlings with a thick stem,www.studiesinmycology.org91