Submitted to: National Soybean Rust Symposium
Publication Type: Abstract Only
Publication Acceptance Date: 10/22/2006
Publication Date: 11/30/2006
Citation: Walker, D.R., Mueller, T.A., Marois, J.J., Wright, D.L. 2006. Investigation of possible soybean genotype × fungicide application rate interactions in Asian soybean rust severity. National Soybean Rust Symposium.( abstract)
Technical Abstract: Asian soybean rust (SBR), caused by the biotrophic fungus Phakopsora pachyrhizi, is one of the most destructive foliar diseases of soybean. SBR can be effectively controlled with fungicides that are currently available, but application costs can be prohibitive, particularly if two or more applications are required. Although no North American soybean cultivars appear to be highly resistant to SBR, field tests conducted in Attapulgus, GA in late 2005 suggested that a University of Georgia breeding line, G00-3209, was more resistant than its sister line G00-3213 to the local P. pachyrhizi isolate. Experiments were conducted in Quincy, FL in 2006 to investigate whether applications of half the recommended rate of the fungicide Headline SBR would control SBR better on G00-3209 than on G00-3213. In addition to the two breeding lines, parents ‘N7001’ and ‘Boggs’ were included in the study. Fungicide treatments consisted of no fungicide applications, application of half the recommended rate of Headline SBR, and application of the full recommended rate. On the basis of severity data, there were no fungicide treatment × soybean genotype interactions, perhaps because application of half the recommended rate of Headline SBR controlled the disease as well as application of the full rate. N7001 had significantly fewer SBR lesions than G00-3213 or Boggs. SBR severity on G00-3209 was intermediate between N7001 and G00-3213, but not significantly different from either. The lower severities on N7001 and both of the University of Georgia breeding lines in comparison to Boggs suggest that a low level of SBR resistance may exist in some high-yielding adapted germplasm.