2010 Annual Report 1a.Objectives (from AD-416) Soybean yields are affected quantitatively and qualitatively by fungi, insects, nematodes, and viruses. The ability of pathogens and pests to colonize and/or infect soybean plants is the result of interactions of pathogen and host genes that allow pathogenic organisms to reproduce and cause disease. The objective of this cooperative research project is to identify and characterize the expression of soybean and pathogen genes involved in the establishment and/or maintenance of disease-causing interactions. 1b.Approach (from AD-416) Candidate soybean genes that support/permit pathogen accumulation or that are involved in pathogenesis will be identified through the genetic analysis of soybean lines differing in their susceptibility to pathogens and pests. In addition, genes expressed at the host-pathogen interface will be identified and characterized using genetic and expression profiling techniques. The involvement of the genes in disease will be confirmed by gene-specific complementation and/or gene silencing. Pathogen genes will be identified by similar genetic and expression profiling techniques. Host and pathogen proteins that physically interact in diseased cells will be identified through in vivo interaction studies and in vitro protein binding and affinity chromatography analyses. 3.Progress Report To develop tools that can be used to understand the mechanisms of resistance of soybean genes for resistance to economically important pathogens and pests, experiments were conducted to produce a virus-induced gene silencing system based on Tobacco streak virus (TSV). The RNA genome of TSV was cloned and modified to accept plant DNA sequences. Short pieces of soybean genes were inserted into the modified virus and soybean plants were inoculated with the recombinant viruses. The stability of the recombinant viruses and their effects on gene expression are being evaluated. Experiments also were initiated to evaluate three additional seed-transmitted soybean-infecting viruses, Alfalfa mosaic virus, Soybean yellow mottle mosaic virus and Tobacco ringspot virus, as possible alternatives to TSV for development of a gene silencing system. The three viruses were isolated from infected soybean plants, and infectious clones were prepared from Soybean yellow mottle mosaic virus. Activities of this project were monitored through meetings, phone calls and e-mails.