Marker-assisted breeding for resistance to common bacterial blight in common bean
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2009 by Nova Science Publishers, Inc. All rights reserved. Common bean (Phaseolus vulgaris L.) has been characterized as a nearly perfect food because of its high protein content and generous amounts of fiber, complex carbohydrates, and other dietary necessities. Common bacterial blight (CBB), incited by Xanthomonas axanopodis pv. Phaseoli (Smith) Dye (Xap), is one of the most destructive seed-borne diseases that affects bean production. Sources of genetic resistance to CBB have been identified in common bean and its related species, tepary bean (P. acutifolius) and runner bean (P. coccineus), but they are inherited as quantitative trait loci (QTL) and vary in the levels of genetic effects and their expression is influenced by environmental conditions. Conventional breeding for resistance to CBB is further complicated by pathogen variability, linkage of resistance with undesirable traits, and different genes conditioning resistance in different plant organs, including leaves, pods, and seeds. With the aid of molecular marker technology, the QTL underlying bean CBB resistance have been tagged using different mapping populations. Molecular markers linked to the QTL have been validated and utilized effectively in bean breeding programs for CBB resistance. In this chapter we reviewed and summarized the progress that has been made in traditional and marker-assisted selection (MAS) breeding of common bean for resistance to CBB. The pros and cons of MAS breeding and its future prospects were discussed.