Protostegia

Cooke Grevillea 9: 19. 1880.
  • Classification: Dothideomycetes, Dothideomycetidae, Capnodiales, Mycosphaerellaceae.
  • Type species: Protostegia eucleae Kalchbr. & Cooke. Slide holotype: IMI 230771. Epitype and ex-epitype cultures: PREM 60879, CPC 23549 = CBS 137232.
  • DNA barcode (genus): LSU.
  • DNA barcode (species): ITS.

Sexual morph unknown. Conidiomata pycnidial, immersed, becoming somewhat erumpent, solitary, exuding a mucoid conidial cirrhus, pale brown, splitting the leaf surface, with central ostiole; conidiomatal wall brown, textura intricata. Conidiophores reduced to conidiogenous cells. Conidiogenous cells hyaline, smooth, lining the inner cavity, lageniform to subcylindrical, proliferating percurrently at apex. Conidia hyaline, smooth, scolecosporous, euseptate (adapted from Crous et al. 2015).

Culture characteristics:

Colonies erumpent, slow growing, with uneven or lobate, feathery margins and sparse to moderate aerial mycelium. On MEA surface and reverse greyish sepia or surface pale olivaceous grey and reverse olivaceous grey; on OA surface mouse-grey or pale olivaceous grey, reverse olivaceous grey; on PDA surface greyish sepia or pale olivaceous grey, reverse mouse-grey or olivaceous grey.

Optimal media and cultivation conditions:

PNA incubated at 25 °C under continuous near-ultraviolet light to promote sporulation.

Distribution:

South Africa.

Hosts:

Euclea divinorum, E. lanceolata, E. natalensis, E. racemosa and E. undulate.

Disease symptoms:

Leaf spots. 

Notes:

The genus Protostegia is thus far only known from South Africa, where it has been reported from leaves of various Euclea spp. However, Euclea is widespread throughout Africa, and therefore Protostegia may be more widespread than currently known. Protostegia was introduced by Kalchbrenner & Cooke (1880) in order to accommodate Stegia magnoliae and the new species Pr. eucleae, and then four more species were allocated in this genus. However, Dyko et al. (1979) transferred three of these species to other genera and another two species were rejected as doubtful. Therefore, only the type species Pr. eucleae was retained and until now this genus has remained monotypic. Protostegia is characterised by immersed conidiomata with walls of textura intricata, splitting the epidermis and appearing acervular, but having a well-developed ostiole (Dyko et al. 1979). Recently, Crous et al. (2015) performed a phylogenetic study based on ITS and LSU sequences including Pr. eucleae. This species was located in the Mycosphaerellaceae together with Cytostagonospora martiniana and Phaeophleospora spp. Cytostagonospora martiniana can be distinguished from Protostegia by having percurrent and polyphialidic conidiogenous cells, and solitary to aggregated conidiomata embedded in stromatic tissue (Quaedvlieg et al. 2013). Phaeophleospora differs by the production of pigmented conidiogenous cells and conidia (Crous et al. 2009).

References:
  • Dyko et al. 1979 (morphology); Crous et al. 2015 (morphology and phylogeny).
  • Crous PW, Carris LM, Giraldo A, et al. (2015). The Genera of Fungi - fixing the application of the type species of generic names – G 2: Allantophomopsis, Latorua, Macrodiplodiopsis, Macrohilum, Milospium, Protostegia, Pyricularia, Robillarda, Rotula, Septoriella, Torula, and Wojnowicia. IMA Fungus 6: 163–198.
  • Crous PW, Summerell BA, Carnegie AJ, et al. (2009). Unravelling Mycosphaerella: do you believe in genera? Persoonia 23: 99–118.
  • Dyko BJ, Sutton BC, Roquebert MF (1979). The genus Protostegia. Mycologia 71: 918–934.
  • Kalchbrenner K, Cooke MC (1880). South African fungi. Grevillea 9: 17–34.
  • Quaedvlieg W, Verkley GJM, Shin H-D, et al. (2013). Sizing up Septoria. Studies in Mycology 75: 307–390.

Table 16. DNA barcodes of accepted Protostegia spp.

Species

Isolates1

GenBank accession numbers2

References

 

 

ITS

LSU

 

Pr. eucleae

CBS 137232ET

KR873252

KR873280

Crous et al. (2015)

Pr. eucleicola

CBS 142615T

KY905668

KY905662

Marin-Felix et al. (2017)

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.

 

  • Crous PW, Carris LM, Giraldo A, et al. (2015). The Genera of Fungi - fixing the application of the type species of generic names – G 2: Allantophomopsis, Latorua, Macrodiplodiopsis, Macrohilum, Milospium, Protostegia, Pyricularia, Robillarda, Rotula, Septoriella, Torula, and Wojnowicia. IMA Fungus 6: 163–198.
  • Marin-Felix Y, Groenewald JZ, Cai, L, et al. (2017). Genera of phytopathogenic fungi: GOPHY 1. Studies in Mycology xxxx.