Simulated Soybean Rust Infections Through Manual Defoliation: Yield and Quality Effects.
Seth Naeve, Univ. of Minnesota, 411 Borlaug Hall, St. Paul, MN 55108, United States of America, Emerson Nafziger, Crop Sciences/W301 Turner Hall, "1102 S. Goodwin, Univ Illinois", Urbana, IL 61801, United States of America, Kurt Thelen, Michigan State University, Michigan State University, A480 Crop & Soil Science, East Lansing, MI 48824, Shawn Conley, Department of Agronomy, 915 West State St, 915 West State St, West Lafayette, IN 47907-2054, United States of America, Bruce Potter, University of Minnesota, SW Research and Outreach Center, 23669 130th St, Lamberton, MN 55152, and Fritz Breitenbach, Univ of Minnesota, UM Extension Southeast Dist Ofc, 863 30th Ave SE, Rochester, MN 55904.
Asian soybean rust (Phakopsora pachyrhizi) has the potential to cause enormous production losses in South America and posses an unknown but potentially significant threat to soybean [Glycine max (L.) Merr.] production in the US. However, little is know about how this pathogen might impact the indeterminate soybean varieties produced in major soybean production ranges of the US. Soybean plants were defoliated to simulate several soybean rust infections scenarios in seven environments in Minnesota, Michigan, Illinois, and Indiana to examine potential yield impacts of the disease. While significant treatment by environment interactions were found, some common responses were noted. Defoliation of the lower one third of canopies at R2 and R4, or two thirds at R2 did not affect yields. Defoliation of the lower two thirds of canopies at R4 and R6 tended to have large and significant yield effects. Yield effects from defoliation of the upper portions of canopies from R2 through R6 were quite mixed. A better understanding of relative importance of various strata of soybean leaves across developmental time to soybean yield formation will help refine management recommendations for soybean rust in indeterminate soybean varieties.