INHERITANCE OF RESISTANCE TO POTYVIRUSES IN PHASEOLUS-VULGARIS L .4. INHERITANCE, LINKAGE RELATIONS, AND ENVIRONMENTAL-EFFECTS ON SYSTEMIC RESISTANCE TO 4 POTYVIRUSES

We have examined the genetics of systemic resistance in Phaseolus vulg aris to azuki bean mosaic virus (AzMV) and cowpea aphid-borne mosaic v irus (CABMV) and the relationship of this resistance to a phenotypical ly similar resistance to watermelon mosaic virus (WMV) and soybean mos aic virus (SMV). In P. vulgaris cv 'Great Northern 1140' (GN1140), res istance to SMV and WMV has been attributed to the genes Smv and Wmv, r espectively, which have been shown to segregate as a unit. Systemic re sistance to AzMV is conferred by two incompletely dominant alleles, Az m1 and Azm2, at unlinked loci. At least three resistance alleles must be present at these two loci for systemic resistance to be expressed i n the plant. Systemic resistance to CABMV in GN 1140 is conditioned by a dominant allele that has been designated Cam2. Under some environme ntal conditions, a recessive allele at an unlinked locus, cam3, also c ontrols a resistant response to CABMV. Resistance to AzMV and CABMV do es not assort independently from Wmv/Smv, but also does not consistent ly cosegregate, suggesting that perhaps in each case one of the factor s involved in resistance is associated with Smv/Wmv.