Polyphasic Approach Utilized for the Identification of Two New Toxigenic Members of <i>Penicillium</i> Section <i>Exilicaulis</i>, <i>P. krskae</i> and <i>P. silybi</i> spp. nov.

• Main Authors: Roman Labuda, Markus Bacher, Thomas Rosenau, Erika Gasparotto, Hannes Gratzl, Maria Doppler, Michael Sulyok, Alena Kubátová, Harald Berger, Kristof Cank, Huzefa A. Raja, Nicholas H. Oberlies, Christoph Schüller, Joseph Strauss
• Format: Article
• Language: English
• Published: MDPI AG 2021-07-01
• Series: Journal of Fungi
• Subjects: cycloheximide tolerance; <i>Penicillium restrictum</i> group; milk thistle; red exudate; secondary metabolites; mycotoxins
• Online Access: https://www.mdpi.com/2309-608X/7/7/557

Two new species, <i>Penicillium krskae</i> (isolated from the air as a lab contaminant in Tulln (Austria, EU)) and <i>Penicillium silybi</i> (isolated as an endophyte from asymptomatic milk thistle (<i>Silybum marianum</i>) stems from Josephine County (Oregon, USA)) are described. The new taxa are well supported by phenotypic (especially conidial ornamentation under SEM, production of red exudate and red pigments), physiological (growth at 37 °C, response to cycloheximide and CREA), chemotaxonomic (production of specific extrolites), and multilocus phylogenetic analysis using RNA-polymerase II second largest subunit (<i>RPB2</i>), partial tubulin (<i>benA</i>), and calmodulin (<i>CaM</i>). Both new taxa are resolved within the section <i>Exilicaulis</i> in series <i>Restricta</i> and show phylogenetic affiliation to <i>P. restrictum sensu stricto</i>. They produce a large spectrum of toxic anthraquinoid pigments, namely, monomeric anthraquinones related to emodic and chloremodic acids and other interesting bioactive extrolites (i.e., endocrocin, paxilline, pestalotin, and 7-hydroxypestalotin). Of note, two bianthraquinones (i.e., skyrin and oxyskyrin) were detected in a culture extract of <i>P. silybi</i>. Two new chloroemodic acid derivatives (2-chloro-isorhodoptilometrin and 2-chloro-desmethyldermoquinone) isolated from the exudate of <i>P. krskae</i> ex-type culture were analyzed by nuclear magnetic resonance (NMR) and liquid chromatography–mass spectrometry (LC–MS).