Proposal to conserve the name Discula (Gnomoniaceae, Diaporthales) with a conserved type

Authors: ALLEN, WILLIAM - North Carolina State University; Castlebury, Lisa; ROSSMAN, AMY - Oregon State University

Submitted to: Taxon
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/18/2016
Publication Date: 5/3/2016
Citation: Allen, W.C., Castlebury, L.A., Rossman, A.Y. 2016. Proposal to conserve the name Discula (Gnomoniaceae, Diaporthales) with a conserved type. Taxon. 65(2):388.

Interpretive Summary: Each year in the United States, fungi destroy billions of dollars of crops, agricultural products, and ornamental and forest trees. In order for scientists to study and control these fungi, it is necessary to have accurate names. Many fungal species have been given more than one name depending on the life stage that was observed, which has led to confusion especially with plant pathogenic fungi. Recently, scientists agreed to use just one scientific name for fungi as with all other groups of organisms. As a result species in the genus Discula, a group of tree pathogens, required name changes. The correct name for the type or reference species for Discula, was determined to belong in a different group, which meant that the name Discula would no longer be used for any fungal species. However, the dogwood anthracnose pathogen, D. destructiva, which is unrelated to that group, would therefore have required an entirely new and unfamiliar genus name. Since the genus Discula was no longer being used by unrelated fungi, it was decided to continue using D. destructiva for this popularly known ornamental tree pathogen. This research is significant because it provides the formal mechanism for retaining the name D. destructiva for the dogwood anthracnose fungus. This work will be used by scientists and plant quarantine officials who need accurate scientific names to communicate about plant pathogens and prevent their movement into new areas.

Technical Abstract: The genus Discula was described by Saccardo (1884) based on the type D. platani as lectotypified by Höhnel (1915). Sogonov & al. (2007) determined that D. platani is a synonym of D. nervisequa, now considered a synonym of Apiognomonia errabunda. Recognizing that Discula and Apiognomonia are synonyms, Rossman & al. (2015) recommended the use of Apiognomonia for this genus. Species of Discula are relatively nondescript asexual morphs most of which belong in the Gnomoniaceae, Diaporthales. Considerable confusion has been associated with species described as Discula many of which are not congeneric with the species that includes the type. Species previously regarded as Discula are scattered throughout the Gnomoniaceae (Castlebury & al. 2002). One species of Discula sensu lato is well known and economically important, namely D. destructiva (holotype:Maryland, Frederick Co., Thurmont Catoctin Mountain Park, on twigs and leaves of Cornus florida, 8 Jun 1990, Redlin, BPI 1107735) the cause of dogwood anthracnose (Redlin 1991). Appearing on the east and west coasts of North America at about the same time, this is an important disease that has devastated both natural and cultivated plants of Cornus spp. including C. florida (Daughtry & al. 1996). At present this disease is known primarily from North America with rare reports from the United Kingdom (Jones & Baker 2007). Although studied thoroughly, the geographic origin of this fungus has never been determined (Caetano-Anolles & al. 2001, Zhang & Blackwell 2002). It is considered a disease of considerable phytosanitary significance (Brasier 2008). In the years following its description D. destructiva was determined to be distinct from the type and other species of Discula, now regarded as belonging to Apiognomonia as well as other genera in the Gnomoniaceae (Castlebury, l.c.; Sogonov & al. 2008, Mejia & al. 2012). These studies show that Discula destructiva does not belong in any previously described genus in the Gnomoniaceae. Given the wide use of this name for the cause of dogwood anthracnose, the synonymy of the type species of Discula, D. nervisequa, with Apiognomonia veneta, and the lack of use of other species in Discula, it seems logical to conserve the name Discula with a new type, D. destructiva, and thus preserve the stability of the use of the scientific name for this economically important and quarantine significant fungus.