Submitted to: Plant Breeding Symposium South African Plant Breeder's Association
Publication Type: Abstract Only
Publication Acceptance Date: January 1, 2002
Publication Date: March 1, 2002
Citation: MIKLAS, P.N. MARKER-ASSISTED SELECTION FOR DISEASE RESISTANCE IN COMMON BEAN. PLANT BREEDING SYMPOSIUM SOUTH AFRICAN PLANT BREEDER'S ASSOCIATION, Vol. 4, p. 14. 2002. Technical Abstract: Marker-assisted selection (MAS) can provide an effective and efficient breeding tool for maintaining and enhancing disease resistance. For common bean, PCR-based RAPD and SCAR markers linked with more than 20 major genes conditioning resistance to angular leaf spot, anthracnose, ashy stem blight, bean common mosaic virus (BCMV), bean golden yellow mosaic virus (BGYMV), and rust, have been obtained to date. Numerous quantitative trait loci (QTL) affecting resistance to ashy stem blight, bacterial brown spot, BGYMV, common bacterial blight, fusarium root rot, fusarium wilt, halo blight, web blight, and white mold, have also been tagged and mapped. Specific applications of MAS in bean includes the retention of the defeated Ur-4 rust resistance gene (resistant to 23 of 89 races of the pathogen) in the presence of the highly effective Ur-11 gene (resistant to 89 of 89 races). Ur-11 is epistatic to less effective resistance genes like Ur-4 and Ur-5. The A14 marker was used to select those Ur-11 lines which retained the Ur-4 gene. The Ur-4 + Ur-11 combination was later found to hold up against a newly identified race in Honduras, whereas Ur-11 by itself was susceptible. Similarly, the hypostatic I gene is retained in the presence of the bc-3 gene by MAS. This combination of a dominant and a recessive gene, possessing different resistance mechanisms, provides for a more durable resistance to BCMV. Rapid deployment of the Co-42 gene for resistance to anthracnose and the bgm-1 gene for resistance to BGMYV into adapted backgrounds was accomplished by marker-assisted backcrossing. As more resistance-linked markers are found, characterized and mapped, the power of MAS for developing more durable disease resistant cultivars will increase substantially.