Identification of random amplified polymorphic DNA markers linked to the Co-4 resistance gene to Colletotrichum lindemuthianum in common bean

New cultivars of the common bean (Phaseolus vulgaris) with durable resistan ce to anthracnose can be developed by pyramiding major resistance genes usi ng marker-assisted selection. To this end, it is necessary to identify sour ces of resistance and molecular markers tightly linked to the resistance ge nes. The objectives of this work were to study the inheritance of resistanc e to anthracnose in the cultivar TO (carrying the Co-4 gene), to identify r andom amplified polymorphic DNA (RAPD) markers linked to Co-4, and to intro gress this gene in the cultivar Ruda. Populations F-1, F-2, F-2:3, BC(1)s, and BC(1)r from the cross Ruda x TO were inoculated with race 65 of Colleto trichum lindemuthianum, causal agent of bean anthracnose. The phenotypic ra tios (resistant/susceptible) were 3:1 in the F-2 population, 1:1 in the BC( 1)s, and 1:0 in the BC(1)r, confirming that resistance to anthracnose in th e cultivar TO was monogenic and dominant. Six RAPD markers linked to the Co -4 gene were identified, four in the coupling phase: OPY20(830C) (0.0 centi morgan [cM]), OPC08(900C) (9.7 cM), OPI16(850C) (14.3 cM), and OPJ01(1,380C ) (18.1 cM); and two in the repulsion phase: OPB03(1,800T) (3.7 cM) and OPA 18(830T) (17.4 cM). OPY20(830C) and OPB03(1,800T), used in association as a codominant pair, allowed the identification of the three genotypic classes with a high degree of confidence. Marker OPY20(830C) which is tightly link ed to Co-4, is being used to assist in breeding for resistance to anthracno se.