Wednesday, November 7, 2007
258-7

Evaluations of Soybean Accessions for Resistance to Soybean Rust in the United States.

David R. Walker1, Randall L. Nelson1, Glen L. Hartman1, Monte R. Miles1, Raymond W. Schneider2, Steve Moore3, David Weaver4, Emerson Shipe5, John D. Mueller6, and H. Roger Boerma7. (1) USDA-ARS Soybean/Maize Germplasm, Pathology and Genetics Research Unit, National Soybean Research Center, 1101 W Peabody Dr, Urbana, IL 61801, (2) Louisiana State University AgCenter, Baton Rouge, LA 70803, (3) AgCenter, Dean Lee Research Station, Louisiana State University, 8105 Tom Bowman Drive, Alexandria, LA 71302, (4) Auburn University, Auburn U. Dept. of Agronomy & Soils, 202 Funchess Hall, Auburn, AL 36849-5412, (5) Box 340315, Clemson University, Clemson University, Dept. of ESPS, Rm 276, P&AS Bldg., Clemson, SC 29634-0315, (6) Edisto Research and Education Center, Clemson University, 64 Research Road, Blackville, SC 29817, (7) 111 Riverbend Road, University of Georgia, University of Georgia Athens, Center for Applied Genetic Technology, Athens, GA 30602-7272

Since the arrival of soybean rust in North America in November, 2004, field evaluations of accessions from the USDA soybean germplasm collection have been conducted at multiple locations in the southern USA. Plant Introductions (PIs) from maturity groups 000 to X have been tested, so late summer planting dates and artificial lighting have been used to compress maturity dates among the entries. Although this has been effective, accessions from early maturity groups still flower sooner after the extended photoperiod is discontinued, so subdivision of the entries into classes composed of PIs from similar maturity groups may reduce bias in interpretation of rating data. Some accessions that appeared relatively resistant in one location/test were more susceptible in others, but several dozen PIs, including representatives from most of the maturity groups, have exhibited high to moderate resistance in all of the field tests as well as in greenhouse assays. Resistance evaluation methods continue to evolve as we learn more about soybean rust and how to assess resistance. Evaluations are being conducted at six locations in five states between Louisiana and South Carolina in 2007. Altogether these data will help to guide plant breeders in making decisions about which sources of resistance appear most appropriate for their breeding programs to develop rust-resistant cultivars adapted to North America.