ARS | Publication request: The Genus Podocrella and Its Nematode-Killing Anamorph Harposporium

Submitted to: Mycologia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 7, 2004
Publication Date: July 1, 2005
Citation: Chaverri, P., Samuels, G.J., Hodge, K.T. 2005. The genus Podocrella and its nematode-killing anamorph Harposporium. Mycologia. 97(2):433-443.

Interpretive Summary: Fungi are useful in the biological control of harmful pests including insects and nematodes. Development of these biological control agents is hindered by lack of systematic knowledge. Many fungi on insects and nematodes are ascomycetes in the Hypocreales that have both a sexual and an asexual state. In this research fungi that attack nematodes were determined to be the Harposporium asexual state of the genus Podocrella. Living cultures of Harposporium were observed in the esophagus of nematodes resulting in their death. Four species of Podocrella and their Harposporium asexual states are described and illustrated. Molecular data were analyzed to determine that these fungi are related to each other and two other genera that occur on insects and nematodes. This research will be used by those working on the development of biological control agents to identify fungi that have potential to control nematodes.

Technical Abstract: Several fungal genera are mentioned in the literature as having similar morphology as the clavicipitaceous genus Podocrella, viz. Atricordyceps, Ophiocordyceps, Wakefieldiomyces, and 'Cordyceps' peltata. These genera have capitate-stipitate stromata that gradually expand into a vertically flattened fertile head that is dark in color, has strongly protruding perithecia, and form asci with eight multiseptate filiform ascospores that disarticulate at the middle septum to form two lanceolate multiseptate part-ascospores. In this study, several specimens of the above-mentioned genera, including the types, were examined in order to determine if they are congeneric with Podocrella. In addition, this study reveals the connection of Podocrella to its anamorph genus, Harposporium, and its relationship to several other clavicipitaceous genera, based on cultural data and large subunit nuclear ribosomal DNA (LSU) sequences. Nematode predation of the Harposporium anamorph of P. peltata is demonstrated. The results show that Podocrella and selected Harposporium LSU sequences form a monophyletic group and that this clade is closely related to Hypocrella. A new species of Podocrella from Costa Rica, P. fusca, is described, new combinations are made for P. peltata and P. harposporifera, and a key to the known species is presented.