PROGRAM OBJECTIVES

The Role of RAPD Markers in Breeding for Disease Resistance in Common Bean

James D. Kelly¹* and Phillip N. Miklas²

¹Crop and Soil Sciences, Michigan State University,
East Lansing, MI 48824, USA

²USDA-ARS-IAREC, 24106 N. Bunn Rd.,
Prosser WA 99350, USA.

ABSTRACT

Diseases are regarded as the leading constraint to increased common bean (Phaseolus vulgaris) production worldwide. Despite the range in variability and complexity among bean pathogens, single gene and quantitative resistance sources are known. Combining these resistance sources into commercial cultivars is a major challenge for bean breeders. To assist breeders, a major effort to identify RAPD markers tightly linked to different genes was undertaken. To date, 30 RAPD and six SCAR markers linked to 18 different genes have been identified, in addition to QTL conditioning resistance to seven major pathogens of common bean. [A complete list of SCAR markers in beans can be found at P. Miklas’ web site www.usda.prosser.wsu.edu ] We review the feasibility of using marker-assisted selection to incorporate disease resistance into common bean. Indirect selection of single resistance genes in the absence of the pathogen and the opportunity afforded breeders to pyramid these genes to improve their longevity and retain valuable hypostatic genes is discussed. The role of markers linked to the QTL controlling complex resistance and the potential to combine resistance sources using marker based selection is reviewed. Improved levels of selection efficiency are demonstrated using flanking markers, repulsion-phase linkages, co-dominant marker pairs, recombination-facilitated markers and RAPD-derived ASAP and SCAR markers. Marker-assisted selection for disease resistance in common bean clearly provides opportunities to breeders which were not feasible with traditional breeding methods.

Abstracted from: Kelly, J.D., and P.N. Miklas. 1998. The role of RAPD markers in breeding for disease resistance in common bean. Molecular Breeding 4:1-11.

J. D. Kelly^a*, P. Gepts^b, P.N. Miklas^c, and D.P. Coyne^d

^aCrop and Soil Sciences, Michigan State University, East Lansing MI 48824;

* Corresponding author. Tel: 517-355-0205; fax: 517-353-3955. Email address: kellyj@msu.edu

^bAgronomy and Range Science, University of California, 1 Shields Avenue, Davis, CA 95616-8515;

^cUSDA-ARS-IAREC, 24106 N. Bunn Rd., Prosser WA 99350;

^dDept. of Agronomy and Horticulture, University of Nebraska, Lincoln, NE 68583

Key words: domestication, disease resistance, epistasis, indirect selection, introgression, linkage, pathogens, Phaseolus vulgaris, plant breeding, Vigna unguiculata

ABSTRACT

Bean/Cowpea Collaborative Research Support Program (B/C CRSP) scientists have successfully developed integrated consensus maps of the 11 linkage groups in both bean (Phaseolus vulgaris L.) and cowpea (Vigna unguiculata L. Walp). The bean map is approximately 1200 cM with some 500 markers and an additional 500 markers shared with other bean maps. The cowpea map spans 2670 cM with over 400 markers. In addition to molecular markers, both maps include map locations of defense genes and phenotypic traits for disease and insect resistance, seed size, color and storage proteins, pod color and those traits associated with the domestication syndrome in bean. Since the bean and cowpea maps were developed independently, linkage groups with the same number probably refer to non-syntenic groups. Map locations of major resistance genes in bean are revealing gene clusters on linkage groups B1, B4, B7, and B11 for resistance to bean rust, anthracnose, common bacterial blight and white mold. Gene tagging and marker assisted selection for disease resistance has progressed to a point where the indirect selection for resistance to a number of major diseases is now routine in bean breeding programs both in the U.S. and overseas.

Abstracted from: Kelly, J.D., P. Gepts, P.N. Miklas, and D.P. Coyne. 2003. Tagging and mapping of genes and QTL and molecular marker-assisted selection for traits of economic importance in bean and cowpea. Field Crops Res. 82:135-154.

Table 1. RAPD markers linked to major disease resistance genes in common bean.

MarkersFig1.pdf