Submitted to: Mycologia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/22/2007
Publication Date: 4/14/2008
Citation: Horn, B.W., Peterson, S.W. 2008. Host specificity of Eupenicillium ochrosalmoneum, E. cinnamopurpureum and two Penicillium species associated with the conidial heads of Aspergillus. Mycologia 100(1):12-19.
Interpretive Summary: Fungi belonging to the genus Aspergillus are of great importance to agriculture because of their ability to infect crops and produce toxins. Aspergillus flavus is the main producer of carcinogenic aflatoxins in peanuts, corn, cottonseed, and tree nuts. Aspergillus niger also infects these crops and can produce ochratoxin. In this paper, four fungi belonging to the genera Eupenicillium and Penicillium were examined for their ability to grow on the spore-producing structures of Aspergillus and thereby interfere with their ability to reproduce. The Eupenicillium and Penicillium species were shown to be host specific and restricted to either A. flavus or A. niger. The two Penicillium species used in this study are new to science. It is important to understand the interactions of toxic Aspergilli with other fungi in nature to devise novel strategies for their control.
Technical Abstract: The genus Penicillium comprises species that mostly colonize plant matter. However, early reports suggest that several species are capable of parasitizing Aspergillus and sporulating on the conidial heads of the host. More recently Eupenicillium ochrosalmoneum and E. cinnamopurpureum, both with Penicillium anamorphs, have been observed sporulating on the heads of Aspergillus species belonging to section Flavi during the colonization of peanut seeds. Little is known about the host specificity underlying these Aspergillus-Penicillium associations. In this study, Aspergillus species representing nine taxonomic sections were paired in culture with E. ochrosalmoneum, E. cinnamopurpureum, and two new species described here based on morphological and molecular characters, P. exiguum and P. georgiense. Phylogenetic analysis of three-locus DNA sequence data showed that P. exiguum is a sister species of E. cinnamopurpureum and that P. georgiense is not closely related to P. exiguum or either of the Eupenicillium species, though its precise phylogenetic placement within the genus Penicillium is unresolved. Eupenicillium ochrosalmoneum, E. cinnamopurpureum, and P. exiguum sporulated predominantly on the heads of section Flavi species. In contrast, P. georgiense was restricted to the heads of section Nigri species. All species spread across Aspergillus colonies by means of aerial hyphae that grew from head to head. Additional studies are required to clarify whether the Eupenicillium and Penicillium species are parasitic or simply epibiotic on their hosts.