Rhizoctonia sapphoae (Y.P. Tan) O’Donnell, R. P., Linde, C. C. & May, T. W., 2025

O’Donnell, R. P., Linde, C. C. & May, T. W., 2025, Rise up, Rhizoctonia: moving to one fungus, one name in the Ceratobasidiaceae (Agaricomycetes, Cantharellales), Persoonia 54 (1), pp. 285-325 : 312

Rhizoctonia sapphoae (Y.P. Tan) R.P. O’Donnell, C.C. Linde & T.W. May, comb. nov. MB 856696

Basionym: Ceratobasidium sapphoae Y.P. Tan , Index of Australian Fungi 41: 5. 2024.

Type citation: ‘ Australia, Queensland, Gatton, from stem rot of Trifolium repens ( Fabaceae ), 7 Jun. 1996, J. Mackie (holotype BRIP 27716a permanently preserved in a metabolically inactive state).’

ITS barcode. PQ061108 ( T).

UNITE 1.5 % SH: n/a.

Notes: The ITS sequence from the type of Rhizoctonia sapphoae is 96.7 % similar to that of R. myrtisiae , which we equate with AG-Fa. No morphological information was provided with the description of R. sapphoae and it and R. myrtisiae were described on the basis of single collections. The accompanying phylogenetic tree ( Tan & Shivas 2024) did not include any other closely related sequences, making it impossible to assess where the cut-off for species delimitation lies in this lineage. We note that the ITS sequence from the type of R. sapphoae also has high BLAST matches against sequences identified as AG-F in various studies, as for example the 98–100 % matches against sequences assigned to AG-F by Muzhinji & Lekota (2024: e.g. GenBank MK442087 at 100 %), but specifically against AG-F when treated as a separate but sister clade to Ag-Fa. Combining subgroups of AG-F, Sharon et al. (2008), tabulated 90–100 % within group variation, indicating that further species-level taxa are likely to be found among isolates assigned to AG-F. A phylogenetic study of a wide range of isolates assigned to AG-F – including sequences from types of names such as R. sapphoae – would be instructive.