Identification of RFLP markers linked to the white rust resistance gene (Acr) in mustard (Brassica juncea (L.) Czern. and Coss.)

White rust and staghead, caused by Albugo candida, is an economically important disease of Brassica juncea and Brassica rapa crops in western Canada. The identification of genes for white rust resistance in these crops and the development of molecular markers for these genes will allow the rapid identification of resistant germplasm and should accelerate the development of white rust resistant cultivars. In this study, 119 F 1 -derived doubled-haploid progeny lines of a cross between white rust susceptible (J90-4317) and white rust resistant (J90-2733) B. juncea lines were evaluated for resistance to A. candida race 2. A single gene (Acr) responsible for conferring resistance to this pathogen was mapped on a densely populated B. juncea RFLP map developed earlier. A cosegregating RFLP marker (X140a) and two other closely linked RFLP markers (X42 and X83) were identified; the latter two markers were 2.3 and 4 cM from the Acr locus, respectively. These markers may be useful for marker-assisted selection and map-based cloning of this gene.Key words: Brassica juncea, mustard, Albugo candida, white rust, disease resistance, RFLP.