Pleiochaeta

(Sacc.) S. Hughes, Mycol. Pap. 36: 39. 1951.

• Synonym: Ceratophorum subgen. Pleiochaeta Sacc., Syll. fung. (Abellini) 11: 622. 1895.
• Classification: Dothideomycetes, Pleosporomycetidae, Pleosporales, Dothidotthiaceae 
• Type species: Pleiochaeta setosa (Kirchner) S. Hughes. Epitype and ex-epitype culture designated here: CBS H-23058, CBS 496.63 = MUCL 8091).
• DNA barcode (genus): LSU. 
• DNA barcode (species): ITS.

Sexual morph unknown. Conidiophores macronematous, mononematous or grouped in fascicles, simple, erect, straight to flexuous, or geniculate, hyaline to pale olivaceous, smooth. Conidiogenous cells mono- and polyblastic, integrated, terminal and intercalary, cylindrical. Conidia solitary, dry, subcylindrical to fusoid, mostly curved, narrowed to obtuse at the apex, truncate at the base, pale to dark brown, smooth, multiseptate; apical cell bears several long, hyaline, subulate appendages which are sometimes branched. Chlamydospores present or absent, brown to dark brown in chains or in groups.

Culture characteristics:

Colonies on PDA grey to olivaceous black with aerial mycelium white, cottony, margin fimbriate, effuse; reverse black.

Optimal media and cultivation conditions:

MEA, OA, PDA or SNA with sterilised twigs, incubated at 25 °C. Not all strains sporulate well in culture.

Distribution:

Worldwide.

Hosts:

Mainly pathogens of legumes, with one species reported from carrots.

Disease symptoms:

Brown leaf spots, lesions are circular and zonate. It also can attack stems, pods and roots, and destroy whole plants.

Notes:

Pleiochaeta was established by Hughes (1951) to accommodate two species previously included in Ceratophorum, namely Plei. setosa and Plei. albizziae. Currently this genus comprises six species including pathogens and saprobes. Pleiochaeta setosa, the generic type, is the most important species from a phytopathogenic point of view, causing serious damage in Lupinus spp. and other legumes members of Fabaceae. Molecular data in this genus is poorly represented. This is the first time that several isolates of different species of Pleiochaeta are subjected to a phylogenetic study. After the analysis of LSU and ITS sequences of the isolates studied with distinct members of Pleosporales (Dothideomycetes), we confirm the phylogenetic position of Plei. setosa and Plei. ghindensis in the Dothidotthiaceae. Furthermore, our results allow us to describe a new species from South Africa, Plei. carotae, causing a disease on carrot leaves. Cultures of Plei. albiziae, Plei. amazonensis, Plei. cassiae and Plei. stellaris were not available for this study, and their phylogenetic position remains unknown. Further studies with additional molecular data of isolates from different origins and substrates, as well as pathogenicity tests, need to be conducted.

References:

• Hughes 1951 (taxonomy and morphology); Pirozynski 1974 (morphology and distribution); Bateman 1997 (pathogenicity); Yang & Sweetingham 2002 (morphology and pathogenicity).
• Bateman GL (1997). Pathogenicity of fungi associated with winter loss and injury in white lupin. Plant Pathologist 46: 157–167.
• Hughes S (1951). Studies on microfungi III. Mastigosporium, Camposporium and Ceratophorum. Mycological Papers 36: 1–45.
• Pirozynski KA (1974). Pleiochaeta setosa. Fungi Canadenses No. 12.
• Yang HA, Sweetingham MW (2002). Variation in morphology and pathogenicity of Pleiochaeta setosa isolates from Lupinus spp. and other legumes. Australasian Plant Pathology 31: 273–280.

Table 14. DNA barcodes of accepted Pleiochaeta spp.

¹CBS: Westerdijk Fungal Biodiversity Institute, Utrecht, the Netherlands. ^T and ^ET indicate ex-type and ex-epitype strains, respectively.

²ITS: internal transcribed spacers and intervening 5.8S nrDNA; LSU: partial 28S large subunit RNA gene.

• Marin-Felix Y, Groenewald JZ, Cai, L, et al. (2017). Genera of phytopathogenic fungi: GOPHY 1. Studies in Mycology xxxx.
• Simon UK, Groenewald JZ, Crous PW (2009). Cymadothea trifolii, an obligate biotrophic leaf parasite of Trifolium, belongs to Mycosphaerellaceae as shown by nuclear ribosomal DNA analyses. Persoonia 22: 49–55.