Bc-1 and bc-u - Two loci controlling bean common mosaic virus resistance in common bean are linked

Resistance to bean common mosaic virus (BCMV) strain NY15 (Zaumeyer) and be an common mosaic necrosis virus (BCMNV) strain NL-3 (Drijfhout) was assesse d in 98 F-5:6 recombinant inbred lines (Ras) derived from a cross between p into bean (Phaseolus vulgaris L.) cultivars 'Olathe' and 'Sierra'. 'Olathe' has bc-u and bc-1(2) whereas 'Sierra' has no known resistance genes. The d ifferentiation of resistant and susceptible lines was based on,visual sympt oms, virus titer, and top dry weight. Forty-seven RILs were moderately resi stant to NL-3, while 51 RILs were susceptible. This segregation fits a 1 su sceptible : 1 resistant ratio characteristic of a single gene. Sixty-nine R ILs were susceptible to NY15, while 29 RILs were resistant, which fits a 3 susceptible : 1 resistant ratio characteristic of a two-gene model. Moderat e resistance to NL-3 was conferred by bc-1(2) with Or without be-re present . Bulked segregant and two point linkage analysis identified randomly ampli fied polymorphic DNA (RAPD) markers linked in coupling to the Bc-1 and Bc-u alleles, The OH14(1100) RAPD marker was 4.5 cM from the Bc-1 locus. The OC 16(1000) RAPD marker was linked at a distance of 10.9 cM from the Bc-u locu s. Multipoint analysis, using segregation data for bc-1(2),bc-u, and the tw o markers, estimated the distance between the Bc-1 and Bc-u loci as 22.8 cM .