Christina Cowger
USDA-ARS Plant Sciences Research Unit
Assistant Professor
Plant Pathologist/Epidemiologist
- Ph.D. (Plant Pathology), Oregon State University
- MS (Botany and Plant Pathology, with minor in Crop Science),
Oregon State University
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 include:
- Investigation of the U.S. 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:
- We are developing virulence profiles of mildew isolates
gathered throughout the region to facilitate breeding for
resistance.
- We are 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.
- We are investigating approaches to improve durability of
resistance genes in commercial varieties.
- 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 20% of the 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.
- Understanding the role of sexual reproduction
in the initiation of Southeastern epidemics of Stagonospora
nodorum blotch (SNB) of wheat. It is controversial whether
this much-studied pathogen produces a sexual stage (Phaeosphaeria
nodorum) in the eastern U.S., and what are the relative contributions
of debris, infected seed, and airborne ascospores to SNB epidemics.
- We have found the teleomorph in North Carolina wheat debris,
and have conducted mating-type studies on North Carolina populations.
- We are comparing artificial inoculation techniques in order
to enhance breeding for SNB resistance, and are coordinating
eastern U.S. uniform nursery work.
- Research on the 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.
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