Rhizoctonia noxia (Donk) Oberw. et al.

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 : 308-309

Rhizoctonia noxia (Donk) Oberw. et al. , Mycol. Progr. 12 (4): 774. 2013.

Basionym: Koleroga noxia Donk, Fungus, Wageningen 28: 35. 1958.

Synonym: Ceratobasidium noxium (Donk) P. Roberts, Rhizoctonia-Forming Fungi (Richmond): 48. 1999.

Type citation: ‘that portion of the type of Pellicularia Koleroga Cooke ( K) represented by the hyphae giving rise to basidia and spores illustrated by Burt (in Ann. Missouri bot. Gdn 5: 124 f. Ia. 1918; 13: 293 f. Ia. 1926).’ Roberts (1999) selected a lectotype: ‘ INDIA: Mysore, on living leaf of Coffea , 1875, ex herb, M. C. Cooke, ex herb. M. J. Berkeley, K ( M) 29396, lectotype (!).’ ( Roberts, 1999).

ITS barcode: EU810056 ( R).

UNITE 1.5 % SH: SH0987559.10FU.

Alternative markers: ATP6 = DQ301584 (R); RPB2 = DQ301715 (R); TEF 1 = DQ301653 (R).

Notes: Representative sequences listed here for R. noxia were generated from a culture isolated by the Indian phytopathologist M.J. Narasimhan (1891–1970) from black rot of a Coffea sp. from India (CBS 154.35). Ceresini et al. (2012) cite CBS 154.35 as the ‘ type strain’ for Cb. noxium , but we have been unable to locate any further literature which designates it as such. It does not appear to represent type material, but given the identical geographic location and host, we associate the culture with this name.

Pellicularia koleroga was introduced for a fungus growing on leaves of Coffea with a gelatinous sporophore. Because some mycologists who examined authentic material of P. koleroga found a mixture of hyphae from one fungus (consistent with Ceratobasidium ) with spores from another unrelated fungus, Donk (1954) considered the name P. koleroga to be a “nomen confusum” (and therefore to be rejected) and specified the portion of the original material with basidia as the type of his newly introduced name Koleroga noxia . The term “nomen confusum” was referred to in the International Code of Botanical Nomenclature in editions up to the Amsterdam Rules of 1950 in connection with taxa whose “characters were derived from two or more entirely discordant elements”. In subsequent editions the term nomen confusum did not appear, but the provision about discordant elements was retained (such as in the Montreal Code of 1961). In such circumstances, a name could be rejected. However, Article 70, dealing with discordant elements, was deleted by the Leningrad Congress and does not appear in the 1978 Leningrad Code. Under the current Code, the interpretation of names is via types and a name cannot simply be rejected because the type material is thought to contain discordant elements. Rogers (1951) typified Pellicularia koleroga on the portion of the type specimen that gives rise to and includes the basidia, as illustrated by Burt (1918). Donk (1954) considered that if a typification was to be carried out (which he argued was not necessary) it should have been done by reference to the spores. The Coffea leaf among Cooke’s original material of Pellicularia koleroga , from which Burt prepared the illustration, appears not to have survived, with Roberts (1999) stating: “A leaf-shaped stain was all that was left of what was possibly the specimen illustrated by Burt and noted as in unusable condition” (p 50). Consequently, Roberts (1999) selected a lectotype for K. noxia from among other leaves of Coffea at K. However, these leaves are not strictly original material of Donk’s name, as the name was not a nomen novum, replacing Pellicularia koleroga , but a new name introduced because Donk considered P. koleroga to be illegitimate. Strictly speaking, K. noxia was typified only by the illustrated material and the lectotype chosen by Roberts (1999) and it is not Code -compliant. Typification of P. koleroga also remains to be settled in terms of whether or not to accept the choice of type by Rogers (1951). Thus, Pellicularia koleroga remains a potential earlier name for K. noxia (which is typified by material, at least in part, that is intimately related to original material of P. koleroga ). Given that there is still usage of the “ koleroga ” epithet for the coffee web-blight, albeit under older generic names, such as in Corticium koleroga [for example by Gidisa et al. (2024)], should Pellicularia koleroga be shown to be an available name that must displace K. noxia , there is not necessarily a clear case for proposing conservation of K. noxia over P. koleroga . Re-examination of remaining original material at K is required, along with an analysis of the phytopathological literature on the prevalence of the competing names for the coffee disease caused by P. koleroga / Koleroga noxia , before finalising the nomenclature of the species. For the moment, we follow Roberts’ (1999) choice to take up the epithet “ noxia ” in his monograph of Rhizoctonia -forming fungi and make the necessary new combination in Rhizoctonia .