This past growing season, as part of a United Soybean Board-funded effort, personnel from Southern Illinois University, Iowa State University and University of Illinois evaluated more than 580 soybean varieties from 22 seed companies in sudden death syndrome (SDS) variety trials. The varieties that were evaluated ranged from the very early (MG 0) to late (MG V) maturity groups. Maturity groups were divided into early and late categories; for example, MG II was split into early (2.0 to 2.4) and late (2.5 to 2.9) categories in order to more easily monitor crop development and assess disease at the appropriate growth stage (Figure).
At one or more locations in Illinois and/or Iowa each variety within a maturity group category was randomly assigned to a two-row plot within a block (replication). Each variety was planted in three replications. Production of the crop within these trials followed University Extension recommendations and was similar to soybeans produced in any Midwestern farm field with a couple of exceptions: 1) to provide a disease-favorable environment irrigation water (where available) supplemented rainfall, and 2) to increase the chance that germinating seedlings would be exposed to the pathogen, at planting time sorghum seed infested with Fusarium virguliforme, the fungus that causes SDS, was placed in-furrow.
Plots were monitored throughout the growing season for growth and development. At the R6 or full seed growth stage, disease incidence and severity ratings were collected for each plot. In each maturity group category, varieties known to have high levels of SDS resistance or susceptibility were included as 'checks'. Sufficient disease in the susceptible check varieties was required in order for data from a particular trial to be included in the final report.
The final report is available for download here. While the data may be of use to crop producers to use as a reference when making their 2017 seed selections or for crop advisors or seed company representatives to use when advising their clients, the final report is forthcoming about its limitations:
"Data presented here is from a single year at one or two locations. Varieties may perform differently in other environments."
"Plots were not harvested for yield in this program because yield comparisons can be misleading from disease nurseries utilizing small plots. Accurate yield data for commercial varieties should be obtained from state variety trials."