Highly sensitive immunoassays for detection of barley stripe mosaic virus and beet necrotic yellow vein virus

Enzyme immunoassays based on the use of monoclonal antibodies (MAbs) were developed for the detection of the barley stripe mosaic virus (BSYVV) and the beet necrotic yellow vein virus (BNYVV). Assays employing conjugates of MAbs to horseradish peroxidase (HRP) were compared to systems with biotinylated MAbs and streptavidin conjugated either to monomeric HRP or to HRP homopolymers with different polymerisation degrees including those of 20, 40 and 80. In the ELISA with streptavidin-polymeric HRP conjugates the assay detection limit was about 12-25 times as good as in the monoclonal double antibody sandwich ELISA. The system for BSMV detection with polymeric HRP was sufficiently sensitive to detect a single infected seed among more than 10(4) healthy ones. The assay detection limit was 1 ng/ml. The immunoenzyme system for BNYVV allowed virus detection in 1:12000 diluted extracts from BNYVV-infected leaves.