Work on Cercospora species on corn and soybeans are new projects. The corn species have been studied by Pedro Crous and his associates, and I have played a minor role. The work on Cercospora sojina is new.

The fungus Phialophora gregata causes an important disease on soybeans, brown stem rot, a vascular wilt disease. There has been considerable confusion over the cause of this disease, so we (Joe Steimel, Fakede Workneh and X. B. Yang in Plant Pathology) more precisely defined the causal agent and designated two races (aggressvie and mild) within the Midwestern USA. This pathogen is now considered a species of Cadophora, we have re-evaluated the species in this genus, which now includes anamorphs of discomycetes (Helotiales) and a number of stain fungi that can cause soft rots of wood in the Antarctic and elsewhere.

Crous, P. W., J. Z. Groenwald, M. Groenwald, P. Caldwell, U. Braun, and T. C. Harrington. 2006. Species of Cercospora associated with grey leaf spot of maize. Studies in Mycology 55:189-197.

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Groenewald, M., J. Z. Groenwald, T. C. Harrington, E. C. A. Abeln, and P. W. Crous. 2006. Mating type gene analysis in apparently asexual Cercospora species is suggestive of cryptic sex. Fungal Gen. Biol. 43:813-825.

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Cadophora, wood soft rot

Blanchette, R. A., B. W. Held, J. A. Jurgens, D. L. McNew, T. C. Harrington, S. M. Duncan, and R. L. Farrell. 2004. Wood-destroying soft rot fungi in the historic expedition huts of Antarctica. Apllied and Environmental Microbiology 70: 1328-1335.

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Cadophora,taxonomy

We also re-evaluated the placement of P. gregata in Phialophora and determined it would be better placed in Cadophora, anamorphs of the Helotiales:

Harrington, T. C. and D. L. McNew. 2003. Phylogenetic analysis places the phialophora-like anamorph genus Cadophora in the Helotiales. Mycotaxon 87:141-151. (Jul-Sep 2003)

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Cadophora gregata and brown stem rot of soybean

We have recently identified two races of Phialophora gregata that differ markedly in their aggressiveness to soybean:

Harrington, T. C., J. Steimel, F. Workneh, and X. B. Yang. 2003. Characterization and distribution of two races of Phialophora gregata in the North Central United States. Phytopathology 93:901-912.

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Harrington, T. C., J. Steimel, F. Workneh, and X. B. Yang. 2000. Molecular identification of fungi associated with vascular discoloration of soybean in the North Central United States. Plant Dis. 84:83-89.

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This work has been funded by the Iowa Soybean Promotion Board.