Infestation of diseases is a major constraint of subsistence production and economic yield of common bean. Development of cultivars with improved genetic resistance to pest and diseases is the primary goal of bean breeding programs throughout the world. DNA-marker-based genetic linkage maps have been developed and exploited to identify, tag, and map disease resistance genes and QTL in common bean. The availability of DNA-based markers within the past 20 years has provided new opportunities and challenges to bean researchers. While numerous molecular markers are available, especially for resistance to bacterial, fiingal, and viral diseases in common bean, proportionately a few are routinely used in breeding programs. The recent development of SSRs from coding and non-coding sequences (Blair et al. 2003) and tentative consensus (TC) sequences (McConnell et al. 2006) in common bean have created further opportunities for mapping and tagging genes in breeding program.
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