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Identification of Random Amplified Polymorphic DNA Markers Linked to the Co-4 Resistance Gene to Colletotrichum lindemuthianum in Common Bean

First, second, fourth, and fifth authors: Instituto de Biotecnologia Aplicada à Agropecuária (BIOAGRO), Universidade Federal de Viçosa (UFV), 36571-000 Viçosa, MG, Brazil; first author: Universidade estadual de Mato Grosso (UNEMAT); third author: Empresa de Pesquisa agropecuaria de Minas Gerais (EPAMIG), Viçosa, MG, Brazil; fourth author: Departamento de Bioquímica e Biologia Molecular, UFV, Viçosa, MG, Brazil; and fifth author: Departamento de Biologia Geral, UFV, Viçosa, MG, Brazil

New cultivars of the common bean (Phaseolus vulgaris) with durable resistance to anthracnose can be developed by pyramiding major resistance genes using marker-assisted selection. To this end, it is necessary to identify sources of resistance and molecular markers tightly linked to the resistance genes. The objectives of this work were to study the inheritance of resistance to anthracnose in the cultivar TO (carrying the Co-4 gene), to identify random amplified polymorphic DNA (RAPD) markers linked to Co-4, and to introgress this gene in the cultivar Rudá. Populations F₁, F₂, F_2:3, BC₁s, and BC₁r from the cross Rudá × TO were inoculated with race 65 of Colletotrichum lindemuthianum, causal agent of bean anthracnose. The phenotypic ratios (resistant/susceptible) were 3:1 in the F₂ population, 1:1 in the BC₁s, and 1:0 in the BC₁r, confirming that resistance to anthracnose in the 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 centimorgan [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 OPA18_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 linked to Co-4, is being used to assist in breeding for resistance to anthracnose.