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ARS Home » Research » Publications at this Location » Publication #90102


item O`Donnell, Kerry
item SCHROERS, H.-J.

Submitted to: Canadian Journal of Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/1/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary: Species in the filamentous fungal groups Hypocreales and Clavicipitales contain a number of insect-pathogenic species that are being considered as biocontrol agents as well as some of the most devastating plant- pathogenic and toxin-producing species. The purpose of this study was to characterize the genetic relationships of several insect pathogens to selected plant pathogens of the genus Fusarium and to nonpathogenic strains that look similar under the microscope. Conventional and molecular genetic approaches revealed that the insect-pathogenic species formed separate, discrete groups that are only distantly related to the toxin-producing Fusarium species. Molecular analyses, based on DNA sequence data from several genes, revealed that the morphologically similar nonpathogenic strains are unrelated. Based on the molecular and morphological analyses, these strains were classified in four unrelated genera, including Stanjemonium which is first described in this paper. Results of this study illustrate the importance of molecular genetic analyses in understanding the relationship of insect biocontrol molds to plant pathogenic and toxigenic species, an issue critical to fully evaluating the potential risk these molds pose to human and animal health.

Technical Abstract: Unlike most phialide-producing fungi that liberate a multiplicity of conidia from each conidiogenous cell, only single conidia are formed on phialide-like conidiogenous cells in Aphanocladium, Verticimonosporium and some species of Sibirina. A group of isolates obtained from soil of native Artemisia tridentata (sagebrush) grassland in Wyoming and from desert soil in Iraq, is compared to these genera and classified as a fourth genus, Stanjemonium, honoring Stanley J. Hughes. Phylogenetic analysis of partial nuclear small (18S) and large (28S) subunit ribosomal DNA sequences indicate that Stanjemonium spp. form a monophyletic sister group to Emericellopsis. Sequences from the nuclear 18S and 28S rDNA were too conserved to resolve morphological species of Stanjemonium; however, phylogenetic analysis of Beta-tubulin and translation elongation factor 1-alpha gene exons and introns resolved all species distinguished. Numerous conidiogenous cells or denticles are scattered along the cells of aerial hyphae in Aphanocladium and Stanjemonium spp., very rapidly collapsing in the former, somewhat more persistent in the latter. In Cladobotryum-Sibirina and Verticimonosporium spp., conidiogenous cells are discrete in terminal and intercalary whorls; phialides of the latter taxon are particularly swollen. Two species recognized in both Aphanocladium and Verticimonosporium. Three new species if Stanjemonium are described, and one new combination from Aphanocladium is proposed, along with one new species of Cladobotryum.