Information on the mechanisms by which pathogens manipulate plant physiology and evade plant defenses will allow us to develop novel strategies for disease control. Pathogen virulence molecules that are secreted can be used to design rapid methods for identifying sources of disease resistance in plants. The virulence genes themselves can be used for DNA based disease diagnostic and pathogen detection technologies.
impact statement issue
Plant pathogenic Streptomyces species are the cause of potato scab, a destructive disease that reduces yields and quality of potato where ever this crop is grown. New scab-causing species have emerged in agricultural systems in the United States and in other countries, resulting in increased losses to this disease. Efforts to produce disease resistant potato varieties have been largely unsuccessful, though significant resources have been invested in this effort. Current disease control recommendations include eliminating the use of animal manures, increasing irrigation and reducing soil pH. All of these practices have negative environmental impacts and reduce the sustainability of agricultural systems. Because of its destructive effect on the potato crop and the negative impacts of current disease control strategies, potato scab is of concern to both producers and those interested in sustainable agriculture.
impact statement response
We are investigating the mechanisms by which plant pathogenic Streptomyces cause potato scab and similar diseases. Through molecular genetic analyses, we have discovered clusters of genes that are involved in plant infection. Recently we characterized a pathway for cytokinin biosynthesis; by producing this plant hormone, the pathogen is manipulating plant responses to infection. Another locus codes for an enzyme that breaks down antimicrobial compounds produced by the plant. We have demonstrated that all of these pathogenicity genes lie on a mobilizable fragment of DNA, called a pathogenicity island, that is involved in emergence of new plant pathogens. We are using the genome sequence of several plant pathogens, coupled with functional analysis, to learn how these pathogens penetrate cells and suppress plant defenses.
impact statement summary
We are using molecular genetic and genomic technologies to unravel the mechanisms of pathogenicity in agriculturally important plant pathogenic bacteria, and to determine how new pathogenic species emerge in agricultural systems.