Submitted to: American Society of Agronomy Meetings
Publication Type: Abstract only
Publication Acceptance Date: 3/27/2008
Publication Date: 10/5/2008
Citation: Walker, D.R., Pauls, M.K., Wright, D.L., Marois, J.J., Nelson, R.L., Narvaez, D.F. 2008. Variation in Lesion Characteristics, Densities and Sporulation Levels Among Soybean Germplasm Accessions Resistant to Soybean Rust (Phakopsora Pachyrhizi) [abstract]. American Society of Agronomy 2008 Joint Meeting, October 5-9, 2008, Houston, Texas. 2008 CDROM. Interpretive Summary:
Technical Abstract: The development of reddish-brown (RB) lesions instead of tan lesions on soybean leaves infected by the soybean rust (SBR) fungus, Phakopsora pachyrhizi, is generally considered to indicate at least partial resistance. Lower disease severity and/or lesion density relative to susceptible hosts with a similar maturity rate also indicate resistance. However, recent observations suggest that different plant introductions (PIs) from the USDA’s soybean germplasm collection manifest resistance to SBR through a range of reactions, and that evaluations limited to some of the criteria commonly used to rate reactions to SBR may sometimes be inadequate. The objective of this study was to investigate the variety and reproducibility of the symptoms developed by a set of PIs challenged with SBR isolates. Data were collected for lesion type, lesion density, uredinia per lesion, and level of sporulation relative to susceptible controls. The results suggest that microscopic inspections of infected leaves may be necessary to obtain a comprehensive evaluation of resistance, particularly as manifested by limited sporulation and uredinia development.