Genetics of resistance to the geminivirus, Bean dwarf mosaic virus, and the role of the hypersensitive response in common bean.

Bean dwarf mosaic virus (BDMV) is a single-stranded DNA virus (genus: Begomovirus, family: Geminiviridae) that infects common bean ( Phaseolus vulgaris L.) and causes stunted plant growth, and mosaic and mottle symptoms in leaves. BDMV shows differential pathogenicity in common bean, infecting germplasm of the Andean gene pool (e.g., the snap bean cultivar Topcrop), but not that of the Middle American gene pool (e.g., the pinto bean cultivar Othello). Resistance to BDMV in Othello is associated with development of a hypersensitive response (HR) in vascular (phloem) tissues. In this study, Middle American germplasm representing the four recognized races (i.e., Durango, Guatemala, Jalisco, and Mesoamerica) and the parents of Othello were inoculated with BDMV and a BDMV-green fluorescent protein (GFP) reporter. All genotypes showed partial or complete resistance to BDMV and BDMV-GFP, indicating the widespread distribution of resistance in the Middle American gene pool. A number of BDMV-resistant germplasm did not show the HR, indicating it is not correlated with resistance. In the F(1), F(2), and F(3) of reciprocal crosses between Othello and Topcrop, a single dominant allele, Bdm, conferred BDMV resistance.