About 90% of the major diseases of the most important US crops are caused by soil-borne pathogens and pests. These diseases account for half of all U.S. crop losses - $4 billion annually, and present the largest source of limitation to yield potential, especially in no-till agricultural systems. Most pathogens are presumably kept in check most of the time by the natural soil microbial flora. Agricultural practices and other human activities impact microbial flora, but we have a poor basic understanding of what a healthy soil flora is. My research objective is to develop new strategies to reduce losses due to common scab and other soil borne diseases.
••Biogeography of plant pathogenic Streptomyces
••Biology of soil-borne plant pathogens
••Biology of plant resistance to soil-borne plant diseases
••Soil - plant root (rhizosphere) microbial ecology in relation to plant health and disease
••Innate and inducible defense responses against pathogens in plants; broad-spectrum disease resistance
••Biocontrol and other sustainable methods of plant disease control
••Mechanisms of pathogenicity of gram-positive plant pathogens
Potato Common Scab Research
Several important soil-borne diseases are caused by fungi and bacteria with broad plant host ranges that do not trigger a classic plant defense response. Common scab is one of these diseases. Though it affects most root and tuber crops, its greatest economic impact is in potatoes. Common scab was described more than 100 years ago, but adequate disease control remains elusive. Common scab serves as a microcosm of soil/plant microbial ecology in plant disease. Recent research areas include the variation, distribution and phylogenetic relationships of the ubiquitous gram-positive soil bacteria (Streptomyces species) that cause the disease and the dynamics of the rhizosphere microbial flora during disease development. Current knowledge gaps include plant genetics of common scab tolerance, the physiological basis for the window of vulnerability to common scab during potato tuber development, the mechanisms of gram-positive bacterial infection of plants, and the dynamics of the soil actinomycete flora.