Despite the ubiquity of insect-borne plant diseases in both natural and agricultural systems, relatively little is known about the interactions among plant pathogens, insect vectors, and susceptible plants in the field. The long-term goal of the proposed research is to understand how disease dynamics of the barley yellow dwarf virus (BYDV) depend on the biological interactions between BYDV isolates, aphid vectors, and host plants. Thirty years of data on the fluctuation in relative abundance of the five characterized isolates of BYDV in Ithaca, NY have documented the displacement of a vector specific isolate (MAV) by an isolate transmitted nonspecifically by several aphid vectors (PAV). The objective of this project is to evaluate the potential role of vector dispersal in driving the dynamics of the displacement. The research will consist of field and laboratory experiments designed to address the following questions: (1) How does disease severity induced by the major BYDV isolates affect a plant's attractiveness to aphids? (2) Does plant infection by the various BYDV isolates differentially affect the alate production, fecundity, and survivorship of the two major aphid vectors Sitobion avenae and Rhopalosiphum padi? (3) Does plant infection by different isolates influence aphid dispersal behavior in the field? and (4) Do differences in aphid colonization and dispersal translate into significant effects on isolate spread? This research has implications for the evolution of virus-vector-host plant associations and will contribute vital information on the potential for spread of novel viral isolates and the evaluation of the environmental risks of genetically engineered microorganisms.
