Thursday, November 8, 2007 - 9:15 AM
334-4

Mapping QTL for Resistance to Asian Soybean Rust.

Joe Curley1, Nanda Chakraborty1, Reid D. Frederick2, Glen Hartman3, Randall Nelson3, and B.W. Diers1. (1) Crop Sciences, University of Illinois Urbana-Champaign, 1101 W Peabody, Urbana, IL 61801, (2) Foreign Disease-Weed Science Research Unit, USDA-ARS-NAA, 1301 Ditto Avenue, Ft. Detrick, MD 21702-5023, (3) 1101 W Peabody Drive, USDA-ARS, University of Illinois, Box 19, NSRL, Urbana, IL 61801

Asian soybean rust, caused by Phakopsora pachyrhizi, has potential to severely reduce soybean yields. Several major resistance genes are known, but are specific to fungal strains and have been defeated. Therefore identification of new resistance genes and partial resistance QTL is essential for breeding efforts against soybean rust. In our lab, recent efforts have involved three different mapping populations. Two of the populations were derived from plant introductions (PIs) with resistant red-brown lesions, and the third was derived from a PI with a low number of susceptible tan lesions, suggesting partial resistance. These efforts have resulted in the mapping of what appears to be a different allele at Rpp1 from PI 594538A. We believe that this is a new allele because the resistance gene was mapped to the Rpp1 region from PI 594538A using a rust isolate, ZM01-1, that can overcome the original Rpp1 allele present in PI 200492. The remaining two populations were inoculated with a bulk pathogen population collected near Quincy, FL. In the second mapping population, a resistance gene was mapped from PI 578457A to the Rpp?(Hyuuga) region. In the third population, with PI 084674 as the resistant parent, there appeared to be segregation of reduced numbers of tan lesions.