APS Abstract of Presentation

Characterizing soybean rust resistance in Glycine tomentella
S. CHANG (2), T. A. Steinlage (2), T. Hymowitz (2), G. L. Hartman (1)
(1) USDA-ARS, Urbana, IL, USA; (2) University of Illinois, Urbana-Champaign, IL, USA
Phytopathology 98:S34

Phakopsora pachyrhizi Syd., the causal agent of soybean rust, is a widespread and damaging pathogen found throughout tropical and sub-tropical regions of the world. The pathogen has a broad host range that includes the perennial Glycine species. Some accessions within these species are known to carry single dominant or multiple dominant single genes for resistance to P. pachyrhizi. Our objective was to screen G. tomentella accessions for rust resistance and to evalute the genetics of this resistance. Greenhouse grown G. tomentella plants were spray-inoculated with a soybean rust isolate. Eleven accessions were resistant and three accessions were susceptible, allowing the fungus to sporulate profusely. When screened by a detached leaf assay, four susceptible lines were found. Four resistant accessions and one susceptible accession were reciprocally crossed and F2 progeny were screened for resistance. Segregation analysis indicated that resistance was not the result of a single dominant gene. Thus, rust resistance in G. tomentella may represent multiple unique genes for resistance to P. pachyrhizi not found in soybean.

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