ARS | Publication request: Variation in Soybean Rust Reaction Response in a Set of Resistant Germplasm Accessions

Submitted to: Biennial Conference on Molecular and Cellular Biology of the Soybean
Publication Type: Abstract Only
Publication Acceptance Date: March 11, 2008
Publication Date: July 20, 2008
Citation: Walker, D.R., Narvaez, D., Marois, J.J., Wright, D.L. 2008. Variation in Soybean Rust Reaction Response in a Set of Resistant Germplasm Accessions. 12th Biennial Conference on Molecular and Cellular Biology of the Soybean, July 20-23, 2008, Indianapolis, Indiana. 2008 CDROM.

Technical Abstract: Soybean resistance to soybean rust (SBR), caused by Phakopsora pachyrhizi, is often associated with the formation of reddish-brown (RB) lesions, reduced disease incidence and severity, and/or prolongation of the latent period between infection and sporulation (referred to as “slow rusting”). The appearance of SBR symptoms on different resistant germplasm accessions from a field in Quincy, FL varied considerably in 2007. Nine of the resistant Plant Introductions (PIs) and four susceptible cultivars were subsequently evaluated in the greenhouse to determine whether similar variation would also occur under more controlled conditions. A diverse range of reactions to SBR was also observed in the greenhouse. PI 606440A developed “classic” RB lesions that were 1 mm or greater in diameter, with occasional uredinia but little or no sporulation. Other accessions, such as PI 417089A and PI 567104B developed much smaller (<1 mm) RB or brown lesions, while lesions developed by PI 506947 were often purplish in appearance. Apparent variation in the spread of disease upwards through the canopy and in the amount of chlorosis associated with rust lesions was observed among both the cultivars and the resistant accessions. These results may reflect different mechanisms of soybean resistance to SBR, and possibly differential sensitivity to toxins produced by the pathogen.