Rhizoctonia robertsii R.P. O’Donnell, C.C. Linde & T.W. May

Rhizoctonia robertsii R.P. O’Donnell, C.C. Linde & T.W. May , nom. nov. MB 852078 View Materials .

Etymology: In honour of Dr Peter Roberts who worked extensively on the taxonomy of the Ceratobasidiaceae and other rhizoctonia-forming fungi.

Replaced synonym: Ypsilonidium anomalum P.H.B. Talbot View in CoL , New Phytol. 86 (3): 270. 1980.

Type citation: ‘ Holotypus: Herb. ADW No. 16598 , J. H. Warcup (0708) ... Host: Prasophyllum macrostachyum R. Br. var. ringens (Reichb. f.) A. S. George , near Perth, Western Australia (two isolates) .’

Notes: Roberts (1999) previously considered this species to be conspecific with R. bicornis but considering the specificity of mycorrhizal associations in Prasophyllum ( Warcup 1981, Burns-Balogh 1984, Freestone et al. 2021, 2022, O’Donnell et al. 2024) – the orchid genus from which this species was isolated and typified from – and the disjunct distribution of this species and the type of R. bicornis , we have chosen to resurrect this species. The name Ypsilonidium anomalum was published before Moniliopsis anomala However , we have chosen to retain the epithet anomala for the latter species (which we here formally transfer to Rhizoctonia ) in order to retain continuity with the earlier invalid use of the binomial “ Rhizoctonia anomala ” by Burgeff (1936) which was the basis for the introduction of Moniliopsis anomala by Currah et al. (1990) (see notes for R. anomala ).