Submitted to: National Soybean Rust Symposium
Publication Type: Abstract Only
Publication Acceptance Date: 10/31/2009
Publication Date: 12/9/2009
Citation: Walker, D.R. 2009. Identification and Development of Soybean Rust-Resistant Germplasm [abstract]. In: Proceedings of the National Soybean Rust Symposium, December 9-11, 2009, New Orleans, LA.
Technical Abstract: Soybean cultivars with resistance to soybean rust (SBR; Phakopsora pachyrhizi) would be valuable assets for an integrated disease management program. Researchers from the United States and several South American countries have been striving to identify and confirm germplasm with SBR resistance that can be transferred to high-yielding lines and cultivars. In field evaluations carried out in the southeastern USA between 2005 and 2009, over 100 accessions from the USDA germplasm collection have shown some resistance to at least some North American populations of P. pachyrhizi. Each of these plant introductions was less resistant in certain year-location environments than others, however, indicating possible differences in pathogenicity among P. pachyrhizi populations in the USA. Pathogen diversity has been well documented in Brazil, where resistance conferred by the Rpp1 and Rpp3 genes was overcome by a new isolate of the fungus that appeared in central Brazil in 2003 and spread rapidly to other soybean production regions. Ironically, Rpp1 and Rpp3 continue to provide a higher level of resistance to US isolotes than Rpp2 and Rpp4. The development of elite lines with high levels of durable resistance to SBR has historically proven challenging for breeders, since P. pachyrhizi is adept at evolving rapidly to overcome resistance genes. Nevertheless, the identification of numerous sources of resistance, the discovery of multiple resistance alleles at several of the five reported Rpp loci, and progress in tagging Rpp genes with "breeder-friendly" DNA markers offer improved opportunities to develop soybean cultivars with broad and durable resistance to SBR.