Christina Cowger

USDA-ARS Plant Sciences Research Unit
Associate Professor
Plant Pathologist/Epidemiologist

• Ph.D. (Plant Pathology), Oregon State University
• MS (Botany and Plant Pathology, with minor in Crop Science), Oregon State University

List of Publications

Research Interests

Dr. Cowger investigates the biology, epidemiology, and population genetics of economically important small grain pathogens. Her goal is to contribute to improved, sustainable management practices. Her program interacts closely with breeders, extension personnel, and other pathology and population genetics groups in the eastern U.S. and beyond.

Dr. Cowger has expertise in pathogen adaptation to host resistance; host genotype diversity and its effects on pathogen populations; and epidemiological and disease management implications of pathogen population structure.

Her group conducts research in the laboratory, greenhouse, and at multiple field locations. The lab uses molecular techniques to investigate species identity, phylogeny, population structure, and pathogen life cycles. Epidemiological modeling and classical field-plot research are also carried out.

Current research emphases:

• Investigation of the population structure of Blumeria graminis f. sp. tritici, cause of powdery mildew of wheat. Powdery mildew is a chronic problem in the eastern U.S., and can inflict substantial economic losses on soft red winter wheat producers. Our work is aimed at learning about the pathogen population in order to design more effective management strategies:
  • developing virulence profiles of mildew isolates gathered throughout the region to facilitate breeding for resistance.
  • analyzing the distribution of molecular variation to make inferences about gene flow and population subdivision, using both classical and new, genealogy-based population genetic approaches.
  • postulation and characterization of resistance genes .
• Assessment of wheat variety mixtures (blends) as a tool to manage disease with reduced pesticide use, and stabilize yields across diverse Southeastern environments. Variety mixtures occupy about 15-20% of wheat acreage in the Pacific Northwest and Kansas, but are unknown in the U.S. Southeast.
  • We are evaluating varieties with similar maturities in two-component or three-component mixtures across various Piedmont and coastal-plain sites. Yield, yield-stability, and quality of many mixtures look promising to date.
• Stagonospora nodorum blotch:
  • host resistance and host-selective toxin (HST) interactions in southeastern U.S. wheat germplasm;
  • disease thresholds and decision aids for fungicide application;
  • facilitation of SNB resistance breeding.
• Epidemiology of Fusarium head blight (scab) in wheat. The fungus Fusarium graminearum (= Gibberella zeae) produces mycotoxins, including DON and nivalenol, in the heads of wheat and other small grains. Even low concentrations of DON, or "vomitoxin," cause serious digestive problems in livestock and humans. Our lab receives funding from the U.S. Wheat and Barley Scab Initiative to help clarify what makes for a severe scab outbreak.
  
  • We are investigating the effects of extended post-flowering moisture; cultivars with different levels and types of resistance; and the timing of infection. We are studying the effects of these factors on FHB symptoms, fungal growth, and DON production.

Teaching:

• Dr. Cowger team-teaches PP590/PP790, "Plant Disease Resistance: Mechanisms and Applications" (alternate springs) with Drs. Marshall, Opperman, and Balint-Kurti http://www.pngg.org/pp590_790

Cowger Lab: