EFFECTS OF BARLEY YELLOW DWARF VIRUS ON YIELD AND YIELD COMPONENTS OFDRILLED WINTER-WHEAT

Yield reduction in eight soft red winter wheat cultivars (Triticum aes tivum) in response to barley yellow dwarf (BYDV) infection was evaluat ed in drilled plots. The experiment was conducted in 1993 and 1994 at the Crop Sciences Research and Education Center of the University of I llinois at Urbana-Champaign. Cultivars Caldwell, Cardinal, Clark, Howe ll, IL 87-2834, Tyler, and Pioneer brands 2548 and 2555 were selected for the study based on root system size, yield potential, and adaptati on to local growing conditions. Plots were planted with a six-row dril l to approximate conditions in growers' fields. A split-plot treatment design was used, with treatments as whole plots, and cultivars as sub plots. The three treatments were BYDV-inoculated, natural BYDV infecti on, and a control (sprayed with Cygon to control naturally occurring a phids). Significant yield reductions in inoculated plots indicated the potential for severe yield loss due to BYDV infection under drilled c onditions. The component of yield most severely affected by virus infe ction was number of kernels per spike. Kernel weight was affected but to a lesser extent than kernels per spike. Tiller number was generally not altered by infection but was positively correlated with yield in infected plots. Since kernels per spike and kernel weight were reduced by BYDV infection, it may be possible to select for tolerant genotype s by identifying lines in which these parameters are least affected by BYD disease pressure.