Introgressing white mold resistance from phaseolus species of the secondary gene pool into common bean
White mold (WM) caused by Sclerotinia sclerotiorum (Lib.) de Bary is a severe disease of common bean (Phaseolus vulgaris L.) in North America. Common bean has only partial resistance. However, some accessions of P. coccineus L. and other species of the secondary gene pool (SGP) are highly resistant. The objectives of this study were to (i) introgress WM resistance from the SGP and (ii) compare resistance of interspecific breeding lines (IBL) VCW 54 and VCW 55, developed by congruity backcrossing between ‘ICA Pijao’ and P. coccineus accession G 35172, and VRW 32, derived from recurrent backcrossing of ICA Pijao with P. costaricensis accession S 33720 with known sources of resistance. The three IBL, ICA Pijao, and susceptible (‘Othello’) and resistant (92BG-7, A 195, G 122, I9365–25, ‘ICA Bunsi’, and VA 19) genotypes were screened in the greenhouse in Colorado and Idaho in 2007 and 2008 and in the field in Idaho in 2007. White mold resistance was successfully introgressed from two of the three Phaseolus species (P. coccineus and P. costaricensis) of the SGP. VCW 54 had the highest WM resistance, and VCW 55 and VRW 32 had similar resistance as previously reported. These sources of WM resistance should be introgressed into common bean cultivars.