Characterization of stem rust resistance in wheat cultivar gage

Wheat (Triticum spp.) stem rust, caused by Puccinia graminis f. sp. tritici Eriks. & E. Henn. (Pgt), re-emerged as a devastating disease of wheat because of virulent race Ug99 (TTKSK). Many modern bread wheat ( T. aestivum L.) cultivars grown in North America are susceptible to Ug99 or its derivative races with additional virulence. ‘Gage’, a USDA-University of Nebraska developed hard red winter wheat cultivar, was released in 1963 mainly for its excellent field resistance to leaf rust caused by Puccinia triticina Eriks and stem rust which was superior to another stem rust resistance cultivar, ‘Scout66’. However, Gage’s resistance has not been genetically characterized to facilitate its use in breeding programs. For molecular marker and genetic analysis, we created an F2 population and the corresponding F2:3 and F4:5 families from crosses between Gage and stem rust susceptible cultivar ‘Bill Brown’. Inheritance of seedling resistance to Pgt race QFCSC and molecular marker analysis indicated that genes in addition to Sr2 explain the stem rust resistance of Gage. Using seedling plant infection types from the F2, F2:3 and F4:5 families, we confirmed that at least one dominant and most likely one recessive gene are involved in Gage’s resistance. Seedling resistance genes acted independently of Sr2 since Sr2 is effective only at the adult plant stage. The relationship between adult plant resistance (APR) molecular marker gwm533 for Sr2 and adult plant disease response in the greenhouse indicated that Sr2 and at least one unknown resistance gene are involved in APR as plants without gwm533 indicative of Sr2 appeared resistant. We characterized the stem rust resistance in Gage and identified potential molecular markers linked to seedling resistance