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Genetics

Molecular Mapping of a Locus Controlling Resistance to Albugo candida in Brassica rapa. C. Kole, research associates and professor, Department of Agronomy, University of Wisconsin, Madison 53706; R. Teutonico(2), A. Mengistu(3), P. H. Williams(4), and T. C. Osborn(5). (2)(5)research associates and professor, Department of Agronomy, University of Wisconsin, Madison 53706; (3)(4)associate researcher and professor, Department of Plant Pathology, University of Wisconsin, Madison 53706. Phytopathology 86:367-369. Accepted for publication 30 November 1995. Copyright 1996 The American Phytopathological Society. DOI: 10.1094/Phyto-86-367.

White rust, caused by Albugo candida, is an economically important disease of crucifers. Genetic analysis for resistance to race 2 of A. candida in an F₂ population and a set of F₃ families both derived from a cross between Brassica rapa cultivars Per (resistant) and R-500 (susceptible) revealed that resistance is controlled by a dominant allele at a single locus. White rust resistance was associated with leaf pubescence, which also was governed by a dominant allele at a single locus. The resistance locus (ACA1) was mapped by linkage analysis with 144 restriction fragment length polymorphism (RFLP) loci segregating among the F₃ families. The ACA1 locus was mapped to linkage group 4 and was flanked by RFLP marker loci ec2b3a (5.4 centimorgans [cM]) and wg6c1a (5.0 cM). ACA1 was linked to the leaf pubescence locus PUB1 by 13.3 cM. The linked RFLP markers and leaf pubescence may be useful in introgression and map-based cloning of white rust resistance in B. rapa and its related species.