Emeritus Professor of Plant Pathology

Purdue University
Botany and Plant Pathology, Lilly Hall
915 West State Street
West Lafayette, IN 47907-2054

Retired: October 2006

Area: Soilborne Cereal Diseases - biological and cultural control of soilborne diseases emphasizing mechanisms, rhizosphere ecology and nutrient-disease interactions

Education

Ph.D., Michigan State University, Plant Pathology

Research Interests

Soilborne diseases impose severe restrictions on crop productivity, management flexibility, and production efficiency and are the most difficult diseases to control because of limited genetic resistance and interactions with other components of the soil environment which condition their survival, virulence, or pathogenicity. The primary goal of my research is to optimize production efficiency by controlling these diseases through manipulation of rhizosphere microorganisms, nutrient availability, and genetic potential. This interdisciplinary research includes cooperation with other scientists in academia and industry.

Gaeumannomyces graminis, Fusarium graminearum, Rhizoctonia, and Phythium are the major soilborne pathogens of cereals in Indiana. Effects of specific crop sequence, seeding date, nutrition, tillage, and varietal tolerance interact through the rhizosphere component to either increase or reduce diseases caused by these pathogens. In the process of understanding these interactions and developing cultural disease controls, our research has concentrated on the influence of nutrition of disease. A key element is understanding the physiological effects of each form of N (NH₄ = ammonia, NO₃ = nitrate) and Mn on the plant as a host, pathogen survival and virulence, and microbial interactions in the rhizosphere which condition nutrient availability and influence pathogen survival and virulence. Development of nitrification inhibitors to stabilize N in the ammoniacal form in soil is a result of this research and provides an effective tool for disease control.

Rhizosphere microorganisms (including many soilborne bacterial and fungal pathogens) influence Mn availability through their oxidative or reductive activity. Under N and Mn stress, the plant's defenses associated with phenolics and lignification are compromised. Nitrogen interacts with Mn through root exudates, which not only regulate the composition of the rhizosphere microflora but also regulate siderophore and antibiotic production of potential biological control agents. We have developed rapid, highly specific laser-enhanced techniques to identify microorganisms and, through genetic engineering, can now elucidate many of the microbial interactions involved and mechanisms active in the biological control of disease.

Assistantships and Positions

Please contact me directly for information on assistantships and openings in my program. Follow these links for general information on graduate programs or employment announcements.