Development and Application of Molecular Markers to Breed Common Bean (Phaseolus vulgaris L.) for Resistance to Common Bacterial Blight (CBB) — Current Status and Future Directions

Abstract

Common bean (Phaseolus vulgaris L.) is grown and consumed principally in developing countries in Latin America, Africa, and Asia. It is a major source of dietary protein that complements carbohydrate-rich sources such as rice, maize, and cassava. It is also a rich source of dietary fibres, minerals and certain vitamins (Gepts et al.2008). Common bacterial blight (CBB), incited by Xanthomonas axonopodis pv. Phaseoli (Smith) Dye (Xap), is one of the most destructive bacterial diseases of common bean. CBB is a seed-transmitted disease that is a major yield-limiting factor of common bean production worldwide. CBB can reduce seed quality through staining and browning, which render the bean seed unacceptable for the food processing industry (Yu et al., 2000a). Currently, CBB outbreaks are managed through the use of expensive pathogen free seeds reproduced in certain locations (Scott & Micheals, 1992) and seed treatment with antibiotics such as Streptomycin or via foliar spraying with copper-based compounds (e.g. KocideTM) that are not only costly, but partially effective, and have serious long-term consequences on human and animal health (Forbes & Bretag, 1991; Fininsa, 2003). The exploitation of natural resistance to CBB is the only effective and environmentally sound approach to control this disease in bean production. Sources of genetic resistance to CBB have been identified in common bean and its related species, tepary bean (P. aculifolius) and runner bean (P. coccineus), but most of them are inherited as quantitative trait loci (QTL) and vary in their levels of genetic effects and their expressions are influenced by environmental conditions (Kelly et al.2003; Miklas et al. 2006). However, dominant gene controlling CBB resistance in common bean was also reported (Zapata et al. 2010). Conventional breeding for resistance to CBB is further aggravated by the pathogen variability, linkage of resistance with undesirable traits (Liu et al. 2008), and different genes conditioning resistance in different plant organs, including leaves, pods, and seeds (Jung et al. 1997; Liu et al., 2009; Aggour et al., 1989; Mutlu et al., 2008; Lopez et al., 2006; Mkandawire et al., 2004; Zapata, 1997). The advent of DNA-based molecular marker (MM) technology has provided an efficient selection tool to breeders in plant breeding (Tanksley et al. 1989). Molecular marker can be defined as a gene or a piece