Hidden diversity behind the Lecanicillium-like white colony-forming mycoparasites on Hemileia vastatrix (coffee leaf rust)

Abstract

During surveys for fungal natural enemies of Hemileia vastatrix - the causal agent of coffee leaf rust (CLR) - in its African centre of origin (Cameroon, Ethiopia), as well as in its exotic South American range (Brazil, Paraguay), an eclectic and species-rich mycobiota was encountered. Here, we provide a comprehensive report on an assemblage of "white colony-forming fungi" (WCF), often treated in the earlier literature under the inadequate "label" Verticillium lecanii (=Lecanicillium lecanii). A total of 265 isolates of WCF were provisionally placed in this arbitrary group. We clarified the identity of our assemblage of Lecanicillium-like fungi using a combination of morphological characteristics and sequence data for the large subunit nuclear ribosomal DNA (LSU), translation elongation factor 1-α (TEF) and the largest subunits of RNA polymerase II (RPB1 and RPB2) regions. Fifteen WCF species belonging to eight genera across three hypocrealean families (Bionectriaceae, Clavicipitaceae and Cordycipitaceae) were found parasitizing pustules of CLR. Significantly, Lecanicillium lecanii was not found to be present amongst these taxa. Six species belonged to the known genera - Corniculantispora, Gamszarella, Lecanicillium, Ovicillium, Pleurodesmospora and Simplicillium. Two new genera are described, Bettiolomyces and Hemileiophthora, as well as seven new species, Bettiolomyces urediniophagus, Gamszarella uredinophila, Hemileiophthora denticulata, H. nodosa, Lecanicillium hemileiae, Pleurodesmospora hemileiae and Simplicillium hemileiae. The following known WCF species are recorded here for the first time on pustules of H. vastatrix: Corniculantispora dimorpha, Gamszarella buffelskloofina, Lecanicillium uredinophilum, Ovicillium attenuatum, Pleurodesmospora coccorum and Simplicillium subtropicum. Additionally, the new combination Bettiolomyces epiphytus is introduced for Verticillium epiphytum.