AbstractThe barley accession Q21861 possesses resistance to the stem‐rust (Puccinia graminisf.sp.tritici), leaf‐rust (P. hordei), and powdery‐mildew (Blumeria graminisf.sp.hordei) pathogens. An anther‐culture‐derived doubled‐haploid population was produced from F1plants from a cross of this accession and the susceptible breeding line SM89010 as a means of rapidly and efficiently determining the genetics of multiple disease resistance. The doubled‐haploid population segregated 1:1 (resistant:susceptible) for resistance to the stem rust pathotype QCC indicating the involvement of a single resistance gene, rpg4. Two‐gene (3:1) and one‐gene (1:1) segregation ratios were observed for resistance to the stem‐rust pathotype MCC at low (23–25°c) and high (27–29°C) temperature, respectively. These different segregation patterns were due to a pathotype × temperature interaction exhibited byrpg4andRpg1.another stem‐rust‐resistance gene present in Q21861. One‐gene and two‐gene segregation ratios were observed in reaction to the leaf rust and powdery mildew pathogens. These data demonstrate the utility of doubled haploid populations for determining the genetics of mul