Search Results
A genetic linkage map of 170 RAPD markers mapped across 79 recombinant inbred lines (Dorado and XAN-176) reveal genomic regions that condition multiple disease resistance to fungal (Ashy Stem Blight—Macrophomina phaseolina), viral (bean golden mosaic virus—BGMV), and bacterial (common bacterial blight—Xanthomonas campestris pv. phaseoli) pathogens of common bean (Phaseolus vulgaris). A genomic site on linkage group US-1 had a major effect, explaining 18%, 34%, and 40% of the variation in phenotypic reaction to ashy stem blight, BGMV, and common bacterial blight disease, respectively. Adjacent to this region was a QTL conditioning 23% of the variation in reaction to another fungal pathogen, web blight (Thanatephorus cucumeris). A second genomic site on linkage group US-1 had minor affect on multiple resistance expression to the same fungal (15%), viral (15%), and bacterial (10%) pathogens. It is unknown whether these specific genomic regions represent a series of linked QTL affecting resistance to each disease separately or an individual locus with pleiotropic effect against all three pathogens.
Understanding the genomic associations among disease resistance loci will facilitate breeding of multiple disease resistant cultivars. We constructed a genetic linkage map in common bean (Phaseolus vulgaris L.) containing six genes and nine quantitative trait loci (QTL) comprising resistance to one bacterial, three fungal, and two viral pathogens of bean. The mapping population consisted of 79 F5:7 recombinant inbred lines (RILs) derived from a `Dorado'/XAN 176 hybridization. There were 147 randomly amplified polymorphic DNA (RAPD) markers, two sequence characterized amplified region (SCAR) markers, one intersimple sequence repeat (ISSR) marker, two seedcoat color genes R and V, the Asp gene conditioning seed brilliance, and two rust [Uromyces appendiculatus var. appendiculatus (Pers.:Pers) Unger] resistance genes: one conditioning resistance to Races 53 and 54 and the other conditioning resistance to Race 108. These markers mapped across eleven linkage groups, one linked triad, and seven linked pairs for an overall map length of 930 cM (Kosambi). Genes conditioning resistance to anthracnose (Co-2) [Colletotrichum lindemuthianum (Sacc. and Magnus) Lams.-Scrib.], bean rust (Ur-5), and bean common mosaic virus (I and bc-3) (BCMV) did not segregate in this population, but were mapped by inference using linked RAPD and SCAR markers identified in other populations. Nine previously reported quantitative trait loci (QTL) conditioning resistance to a variety of pathogens including common bacterial blight [Xanthomonas campestris pv. phaseoli (Smith) Dye], ashy stem blight [Macrophomina phaseolina (Tassi) Goid.], and bean golden mosaic virus (BGMV), were located across four linkage groups. Linkage among QTL for resistance to ashy stem blight, BGMV, and common bacterial blight on linkage group B7 and ashy stem blight, BGMV, and rust resistance loci on B4 will complicate breeding for combined resistance to all four pathogens in this population.