Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/9/2006
Publication Date: 1/25/2007
Citation: Patzoldt, M.E., Tyagi, R.K., Hymowitz, T., Miles, M.R., Hartman, G.L., Frederick, R.D. 2007. Soybean rust resistance derived from glycine tomentella in amphiploid hybrid lines and derived fertile soybean lines. Crop Science 47:158-161 Interpretive Summary: Soybean rust, caused by the fungal pathogen Phakopsora pachyrhizi, is a devastating disease in most soybean growing regions throughout the world and was found for the first time in the United States late in the 2004 growing season. While four single rust resistance genes have been described in soybean, Glycine max, no cultivars have been found that are resistant to all rust isolates. Additional rust resistance genes have been identified in wild perennial relatives of soybean, Glycine tomentella. Hybrids generated between G. max and G. tomentella were backcrossed to G. max to create amphiploid hybrid lines. When inoculated with P. pachyrhizi, the amphiloid hybrids retained the rust resistance that had been found in the G. tomentella parent. While making crosses between Glycine perennials and G. max is difficult and time consuming, the rust resistance identified in G. tomentella may prove useful in developing G. max cultivars with broad resistance to soybean rust.
Technical Abstract: Soybean rust (SBR), caused by the fungal pathogen Phakopsora pachyrhizi Syd., has the potential to cause significant economic yield loss in U.S. soybean production. Four single dominant resistance genes have been identified in soybean [Glycine max (L.) Merr.] but only confer specific resistance to a few rust isolates. Additional resistance genes have been identified in wild perennial relatives, including G. tomentella Hayata (accession PI 483218, 2n=78). Intersubgeneric hybrids have been created between G. max (cv. Altona) and this G. tomentella accession. Amphiploid hybrid lines (2n=118) were the result of this hybridization and when further backcrossed to G. max (cv. Clark 63), derived fertile lines (2n=40) were also generated. Both sets of progeny were screened at the USDA-ARS Foreign Disease-Weed Science Research Unit Biosafety Level 3 Plant Pathogen Containment Facility at Ft. Detrick, MD to determine if the resistance to SBR was inherited in the subsequent populations. The amphiploid hybrid clones still retained the genetic SBR resistance that had been found in the G. tomentella parent. However, the derived fertile lines appear to have lost the resistance, probably because there they were not screened for SBR resistance during the backcrosses. Re-instituting the backcross procedure, while testing for SBR resistance at every generation, could move the SBR resistance gene(s) from G. tomentella to the cultivated soybean G. max.