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 wester n Canada. The identification of genes for white rust resistance in the se crops and the development of molecular markers for these genes will allow the rapid identification of resistant germplasm and should acce lerate the development of white rust resistant cultivars. In this stud y, 119 F-1-derived doubled-haploid progeny lines of a cross between wh ite rust susceptible (J90-3317) and white rust resistant (J90-2733) B. juncea lines were evaluated for resistance to A. candida race 2. A si ngle gene (Acr) responsible for conferring resistance to this pathogen was mapped on a densely populated B. juncea RFLP map developed earlie r. A cosegregating RFLP marker (X140a) and two Ether closely linked RF LP markers (X42 and X83) were identified; the latter two markers were 2.3 and 4 cM from the ncr locus, respectively. These markers may be us eful for marker-assisted selection and map-based cloning of this gene.