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Poster: Biology & Disease Mgmt: Genetics of Resistance


Effectiveness of adult plant resistance to wheat stem rust is specific to Puccinia graminis f. sp. tritici race
M. ROUSE (1), J. Briggs (2) (1) USDA-ARS, U.S.A.; (2) University of Minnesota, U.S.A.

Adult plant resistance (APR) in wheat to stem rust caused by Puccinia graminis f. sp. tritici is considered to be conferred by multiple loci that are race non-specific. Our objective was to test the race-specificity of individual and combinations of wheat stem rust APR loci. We evaluated a biparental wheat population (Thatcher/McNeal) that is segregating for six APR loci with minor effects in response to four races of the stem rust pathogen (QTHJC, TPMKC, RCRSC, and QFCSC), in single-race field nurseries over three years. QTL mapping and ANOVA identified the significance and effectiveness of the six minor effect loci across the years and races. The QTL with the largest effect, coincident with the Sr12 locus, was effective to virulent races QTHJC and TPMKC, but conferred a variable, sometimes nonsignificant, response to race RCRSC. The other five QTL varied in effectiveness between years and were generally less effective in response to race RCRSC in particular. The data from QTL mapping suggested that some of the QTL could be race specific, such as QSr.cdl.1AL, because they were detected in response to races such as TPMKC and QTHJC, but not to race RCRSC. This observation has implications specifically for wheat stem rust resistance breeding because it suggests that resistance observations to a single race may not be indicative of resistance to another race, even if the mechanism of resistance is multiple minor effect loci.