Location: Emerging Pests and Pathogens ResearchTitle: Morphology and molecular taxonomy of Evlachovaea-like fungi, and the status of this unusual conidial genus Author
Submitted to: Fungal Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2012
Publication Date: 11/22/2012
Citation: Humber, R.A., Rocha, L., Inglis, P.W., Kipnis, A., Luz, C. 2012. Morphology and molecular taxonomy of Evlachovaea-like fungi, and the status of this unusualconidial genus. Fungal Biology. 117:1-12. Interpretive Summary: This paper deals with Brazilian isolates of fungal pathogens of insects that produce their spores by an extremely unusual means (that results in flat, zipper-like chains of conidia). These fungi can be classified in the genus Evlachovaea which was described in 1999 based primarily on its unique means of forming the conidia. Molecular studies indicated that the gene sequences of fungi that could be classified in Evlachovaea cannot, in fact, be distinguished from those of species in the much older genus Isaria. The major thrust of this manuscript examines the similarities and differences between these genetically similar fungi, determines that Evlachovaea cannot be treated as differing from Isaria, and points out similarity between Evlachovaea-like fungi and some known species of Isaria. Even though few species in either Evlachovaea or Isaria have known sexual stages, newly adopted (but still controversial) rules for fungal nomenclature will soon require the species of both of these conidial fungal genera to be transferred to Cordyceps, a genus defined by its sexual reproductive states, and these obligatory transfers will unavoidably strip much pertinent biological information from the names that will have to be used for these fungi.
Technical Abstract: The entomopathogenic anamorphic genus Evlachovaea was described to differ from other fungi in forming its conidia obliquely to the axis of the conidiogenous cell and with successive conidia having alternate orientations with a zipper- or chevron-like arrangement resulting in flat, ribbon-like chains. Morphological and molecular studies of six Evlachovaea-like isolates baited from Central Brazilian soils using Triatoma infestans (a vector of Chagas disease) and of other entomopathogens with Evlachovaea-like conidiogenesis led to a re-evaluation of the status of this little known fungal genus. The Brazilian isolates formed two distinct groups based on gene sequences for both the internal transcribed spacer (ITS) and translation elongation factor (EF-1a) genes, morphology, and growth patterns; both groups also differed from the type species, Evlachovaea kintrischica. More detailed studies of these fungi indicated that the alternatingly oblique orientations of forming conidia is neither a stable nor invariant character (even on single phialides). Furthermore, the molecular cladistic analysis unambiguously placed the Evlachovaea isolates firmly within the genus Isaria (Hypocreales: Cordycipitaceae). The ITS sequences of E. kintrischica were very similar or even identical to those of I. amoenerosea and I. cateniobliqua, thereby suggesting that E. kintrischica is a synonym of one of these species, and that the genus Evlachovaea must be treated as a later synonym of Isaria, which must now be recognized to include several highly divergent modes of conidiogenesis. These taxonomic findings are discussed in the context of dramatic changes recently imposed on the nomenclatural standards used to determine the correct names of all pleomorphic fungi.