Submitted to: Soybean Research World Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: March 1, 2009
Publication Date: August 10, 2009
Repository URL: http://www.wsrc2009.cn/en/index.asp
Citation: Walker, D.R., Srivastava, P., Marois, J.J., Wright, D.L., Nelson, R.L. 2009. Characterization of Variation in Soybean Germplasm Accession Reactions to Soybean Rust (Phakopsora pachyrhizi)[abstract]. In: Proceedings of the World Soybean Research Conference VIII, August 9-16, 2009, Beijing, China. Available: www.wsrc2009.cn/en/index.asp. Technical Abstract: Disease severity and lesion type are often used to assess soybean (Glycine max) resistance to soybean rust caused by Phakopsora pachyrhizi. Reddish-brown (RB) lesions have been considered indicative of resistance, whereas tan lesions have been been associated with susceptibility. In 2007 field and 2008 greenhouse evaluations conducted in Quincy, Florida (U.S.A.), some soybean germplasm accessions that developed tan-colored lesions did not support sporulation, while other accessions exhibited profuse sporulation from RB lesions. Some accessions, including PI 567104B, had tan lesions that did not form uredinia. Further studies were conducted to confirm and characterize differences between resistant accessions like PI 606440 that developed distinct RB lesions and accessions that developed non-sporulating tan lesions after being challenged with a 2007 isolate from Florida. Observations from these studies suggest that defense mechanisms vary among rust-resistant soybean germplasm accessions, as manifested through differences in lesion color and diameter, and through differences in ratios of lesion densities on the upper and lower surfaces of infected leaves. The results also confirm earlier observations that some highly resistant soybean introductions develop lesions that are distinctly tan in color.