Submitted to: Journal of Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: April 10, 2003
Publication Date: November 1, 2004
Citation: Miles, M.R., Morel, W., Yorinori, J.T., Hartman, G.L., Frederick, R.D. 2004. Preliminary report of glycine max germplasm screened for reaction to soybean rust. Journal of Phytopathology. Technical Abstract: Soybean rust, caused by Phakopsora pachyrhizi H. Sydow & Sydow, was found in the Parana River basin of Paraguay in March 2001. The presence of the disease was confirmed in the 2001-2002 season with reports from Brazil and Argentina. A set of 174 soybean entries that included the ancestral lines of the current US commercial cultivars as well as entries reported to have resistance were inoculated in the greenhouse in Captain Miranda (Paraguay), Londrina (Brazil) and the USDA confinement greenhouse at Ft. Detrick, Maryland (USA). Inoculum consisted of local field collections in Paraguay and Brazil, and a mixture of four collections from Brazil, Paraguay, Thailand, and Zimbabwe in the Maryland evaluations. Rust evaluations were done at R5 to R7 in Paraguay and Brazil, and on 4-week old seedlings in Maryland. Disease ratings were more severe in evaluations done in Maryland when compared to Paraguay and Brazil. Based on first set of results in Paraguay and Brazil some entries were moderately resistant to resistant, including entries with known single genes for resistance. There were no entries classed as resistant in the Maryland evaluation. There were also differences in the ranking of the entries among the three locations. The resistant B reaction type and the susceptible tan reaction were seen on the same leaf with some entries. The apparent virulence diversity seen in this preliminary screen will complicate the development of resistance, as it is an indication that single genes alone may not be effective in controlling soybean rust.