Contact Information

• Warnell School of Forestry and Natural Resources
• Athens, Georgia
• Room:3-527
• Phone:706.542.1205
• Fax:706.542.8356
• covert@uga.edu

Education

A.B. Biochemistry, 1986 Dartmouth College

Ph.D. Bacteriology, 1990 University of Wisconsin-Madison

Area of Specialization

Molecular genetics of fungal-plant interactions.

Prior Positions

• NSF Postdoctoral Research Fellow in Plant Biology
• 1991-1992, Department of Plant Pathology, University of Arizona
• 1992-1993, Department of Genetics, University of Georgia

Adjunct Appointments

• 1994-present, Department of Plant Pathology, University of Georgia
• 1994-present, Department of Genetics, University of Georgia
• 1996-present, Department of Botany, University of Georgia

Courses Taught

Undergraduate

FORS 3040 Tree Physiology and Development

This course covers how trees synthesize and utilize their own food, how they transport water and nutrients internally, and how they grow and reproduce. It also discusses how humans utilize an understanding of these processes to improve trees for practical purposes.

Graduate

FORS 8200 Scientific Research in Forest Resources

This is a practical skills course for graduate students that emphasizes proposal writing and oral presentations. It also includes coverage of the scientific method and standards for good scientific conduct. It is required for all Masters of Science students within the School.

On-Going Research Projects

The research in the Covert lab focuses on two different fungal diseases of pine, pitch canker and fusiform rust. In our study of these problems we are addressing three broad questions:

1. How do fungi cause plant disease symptoms?
2. How do asymptomatic endophytes and obligately biotrophic fungi grow within their host plants?
3. How do fungal pathogens and plant hosts influence each other's development?

Specific aspects of our work and the two diseases we study are described below.

Pitch canker affects many species of pine and is characterized by the presence of resin-weeping cankers, branch die-back, and seedling death. It is caused by the fungus Fusarium circinatum (teleomorph: Gibberella circinata), which is an ascomycete that infects via wounds. Pitch canker is an economically significant disease in the southeastern United States and in South Africa.

Photo:Profuse pitch production on an infected Douglas-fir trunk. (Click here or Photo to enlarge)

It also severely affects the native populations of Monterey pine in California. Much of our early work on this disease focused on developing techniques to manipulate F. circinatum in the lab. Most notably we developed the ability to conduct sexual crosses in vitro, to identify isolates' mating types in a PCR assay, and to transform this species with Agrobacterium tumefaciens.

Photo:Branch die-back on Monterey pine

Currently we are using the A. tumefaciens transformation system to create tagged mutants in F. circinatum. We are screening them for their ability to cause disease on Monterey pine as well as for their ability to grow asymptomatically in plants. This approach should allow us to identify F. circinatum genes that are essential for pitch canker symptom development as well as for in planta growth.

Fusiform rust affects slash pine and loblolly pine, the two most important commercial species of pine in the southeastern United States. It is characterized by the formation of woody galls on the stems and branches of infected trees. Fusiform rust is caused by the fungus Cronartium quercuum f. sp. fusiforme.

Photo:A typical fusiform rust gall encircling the stem of a young pine tree.

This obligate basidiomycete has no free living form in nature and must grow in association with oak leaves as well as with pine wood in order to complete its lifecycle.

Photo:A gall shown in cross section. Approximately 25% of the stem in this sample (at top of image) remains healthy.

We have used both differential display and suppression subtraction hybridization to identify pine genes that are induced or suppressed in response to fusiform rust infection.We hypothesize that these differentially expressed genes play roles in wood growth, host defense or nutrient provision to the pathogen. Experiments with clone arrays and with the Arabidopsis orthologs for selected pine genes are being carried out to test these hypotheses about gene function. We are also using suppression subtraction hybridization to identify C. q. fusiforme genes that are involved in spore development and germination, developmental events that are influenced by host morphology and/or biochemistry.