Crous & W. Gams, Eur. J. Pl. Path. 109: 845. 2003. Fig. 39.

Fig. 39. Oculimacula spp. A–G. Disease symptoms. A, B. Eyespot lodging. C–E. Eyespots. F. Whiteheads of wheat. G. Apothecia of Oculimacula gamsii on wheat stubble. H–K. Sexual morphs of Oculimacula yallundae. H, I. Ascomata. J. Section through the ascoma showing ascal layer. K. Ascus and ascospores. L–O. Asexual morphs. L. Conidia and conidiogenous cells of Oculimacula gamsii. M. Conidial hila and conidiogenous cell of Oculimacula yallundae. N. Conidial hila and conidiogenous cell of Oculimacula gamsii. O. Conidial hila and conidiogenous cell of Oculimacula anguoides. Scale bars: I = 100 μm; J, K = 10 μm; L = 5 μm; M–O = 1 μm.

Synonym: Helgardia Crous & W. Gams, Eur. J. Pl. Path. 109: 845. 2003.

Classification: Leotiomycetes, Leotiomycetidae, Helotiales, Incertae sedis.

Type species: Oculimacula yallundae (Wallwork & Spooner) Crous & W. Gams = Helgardia herpotrichoides (Fron) Crous & W. Gams, basionym: Cercosporella herpotrichoides Fron. Holotype: K(M) 233697. Neotype and ex-neotype strain of Helgardia herpotrichoides designated by Crous et al. (2003): CBS H-23003, CBS 110665.

DNA barcode (genus): LSU.

DNA barcodes (species): ITS, tef1. Table 12. Fig. 40.

Table 12. DNA barcodes of accepted Oculimacula spp.

Species Isolates1 GenBank accession numbers2 References
ITS tef1
Oculimacula acuformis CBS 495.80T MG934455 MG934497 Present study
O. aestiva CBS 114730 MG934454 MG934496 Present study
O. anguioides CBS 496.80T LT990662 LT990618 Present study
O. yallundae CBS 110665NT MG934456 MG934498 Present study
CBS 128.31 MG934457 MG934499 Present study
CBS 494.80 JF412009 MG934500 Tsang (unpubl. data), present study

CBS: Westerdijk Fungal Biodiversity Institute, Utrecht, the Netherlands. T and NT indicate ex-type and ex-neotype strains, respectively.


ITS: internal transcribed spacers and intervening 5.8S nrDNA, tef1: partial translation elongation factor 1-alpha gene.

Fig. 40. RAxML phylogram obtained from the combined ITS (631 bp) and tef1 (575 bp) sequence alignment of taxa belonging to Oculimacula. The tree was rooted to Cadophora melinii. The new combination proposed in this study is indicated in bold. RAxML bootstrap support (BS) values above 70 % and Bayesian posterior probability scores above 0.95 are shown at the nodes. GenBank accession numbers are indicated in Table 12. T and NT indicate ex-type and ex-neotype strains, respectively. TreeBASE: S21899.

Ascomata 0.5–2.5 mm diam, apothecial, sessile, gregarious, circular to lobate, on a subiculum of white to dark brown hyphae, attached to substrate via a superficial mat of pale brown, thin hyphae. Disk smooth, grey with a pale grey margin, becoming emarginate and flattened to convex at maturity. Receptacle pale brown to grey-brown, cup-shaped. Medullary excipulum of multiseptate, hyaline hyphae. Ectal excipulum of thin-walled, dark brown, angular cells, becoming more elongated towards margin. Paraphyses filiform with obtuse ends, similar in length to asci. Asci 8-spored, unitunicate, clavate to subcylindrical or fusoid, with a short stalk, and an apical pore staining blue in Melzer’s reagent. Ascospores bi- to multiseriate, hyaline, smooth, aseptate, fusoid to subcylindrical or clavate with rounded ends, mostly straight. Conidiophores fasciculate or solitary on superficial mycelium, or arising from pale brown stromata, subcylindrical to geniculate-sinuous, rarely branching, hyaline to pale olivaceous, smooth, consisting of conidiogenous cells only, or slightly differentiated with up to 2 septa. Conidiogenous cells integrated, proliferating sympodially at apex, with inconspicuous, dense geniculations; conidiogenous loci unthickened, inconspicuous, not darkened. Conidia solitary, hyaline, smooth, arranged in slimy packets, acicular, filiform, straight to curved, one- to multiseptate, forming smaller, secondary conidia via microcyclic conidiation (adapted from Crous et al. 2003).

Culture characteristics: Colonies with moderate aerial mycelium giving a cottony appearance. On PDA surface grey to olive grey, brownish-grey, pinkish-grey or greenish; reverse grey to greenish-black, greenish, brownish or creamy pink.

Optimal media and cultivation conditions: SNA under continuous near-ultraviolet light at 25 °C.

Distribution: Africa, Australasia, Europe, New Zealand and North America.

Hosts: Poaceae, including Triticum and Hordeum, among others.

Disease symptoms: Eyespot lesions that girdle the stem and soften the stem-base.

Notes: Oculimacula encompasses four species associated with eyespot disease symptoms of cereals in the temperate regions of the world. Eyespot is an important disease of stem bases in which the infection occurs at or near the soil line, attacking chiefly the basal leaf sheaths and internodal tissues of the culms (Sprague and Fellows, 1934, Lucas et al., 2000). The fungus sporulates in the fall and spring producing the disease, and survives the winter on diseased stubble standing or lying in the field (Sprague & Fellows 1934). Disease control relies on the use of fungicides, delayed seeding in the fall and by planting resistant cultivars (Murray, 1996, Douhan et al., 2002).

 Oculimacula was introduced by Crous et al. (2003) to accommodate sexual morphs previously classified in Tapesia, while Helgardia was introduced for the asexual morphs linked to Oculimacula. Johnston et al. (2014) synonymised these generic names and conserved the name Oculimacula because it is most commonly used by plant pathologists for the eyespot diseases of wheat and barley.

References: Sprague & Fellows 1934 (morphology and pathogenicity); Sprague, 1936, Lucas et al., 2000 (pathogenicity); Nirenberg 1981 (morphology and pathogenicity); Crous et al. 2003 (morphology and phylogeny).

Oculimacula acuformis

(Nirenberg) Y. Marín & Crous, comb. et stat. nov. MycoBank MB824638.

Basionym: Pseudocercosporella herpotrichoides var. acuformis Nirenberg, Z. PflKrankh. PflSchutz 88: 244. 1981.

Synonyms: Ramulispora herpotrichoides var. acuformis (Nirenberg) Boerema, et al., Netherlands Journal of Plant Pathology, Supplement 1 98: 22. 1992.

Tapesia yallundae var. acuformis Boerema, et al., Netherlands J. of Pl. Path., Supplement 1 98: 22. 1992. (nom. inval., Art. 40.3, Melbourne).

Ramulispora acuformis (Nirenberg) Crous, S. Afr. J. Bot. 61: 46. 1995.

Tapesia acuformis (Boerema, et al.) Crous, S. Afr. J. Bot. 61: 46. 1995. (nom. inval., Art. 40.3, Melbourne).

Helgardia acuformis (Nirenberg) Crous & W. Gams, Eur. J. Pl. Path. 109: 846. 2003.

Oculimacula acuformis (Boerema, et al.) Crous & W. Gams, Eur. J. Pl. Path. 109: 846. 2003. (nom. inval., Art. 40.3, Melbourne).

Material examined: Germany, Tübingen, from Secale cereale (Poaceae) culm base, 1978, H. Nirenberg (culture ex-type CBS 495.80).

Notes: Oculimacula acuformis was introduced to accommodate Tapesia yallundae var. acuformis (Crous et al. 2003). However, the combination is invalid because the basionym lacks details for the ex-type strain (Art 40.3). We have consequently proposed the new combination based on its asexual morph Pseudocercosporella herpotrichoides var. acuformis. This latter species was transferred to Helgardia in the same publication where Oculimacula acuformis was proposed and when both genera were first introduced (Crous et al. 2003). Helgardia acuformis is a synonym of Oculimacula acuformis.

Authors: Y. Marin-Felix, J.Z. Groenewald & P.W. Crous