Inheritance and Characterization of Angular Leaf Spot Resistance Gene Present in Common Bean Accession G 10474 and Identification of an AFLP Marker Linked to the Resistance Gene
Mahuku, George | Montoya, Carmenza | Henríquez, María Antonia | Jara, Carlos | Teran, Henry | Beebe, Stephen
Angular leaf spot (ALS), caused by the fungus Phaeoisariopsis griseola (Sacc.) Ferr., is one of the most important diseases of common bean (Phaseolus vulgaris L.) in tropical and subtropical bean producing areas. The common bean accession G 10474 has been widely resistant to P. griseola, including pathotype 63-63, one of the most virulent P. griseola pathotypes characterized. The objectives of this study were to determine the inheritance of angular leaf spot resistance and to identify molecular markers linked to the resistance gene in G 10474. Resistance to P. griseola pathotypes 63-63 in G 10474 was investigated in F₂ populations derived from a cross between G 10474 and Sprite (universally susceptible). Inoculation of parents, F₁, F₂, and backcross-derived plants with race 63-63 revealed that a single dominant gene conditioned ALS resistance in G 10474. A combination of the amplified fragment length polymorphism (AFLP) technique and bulked segregant analysis (BSA) was applied to the F₂ population to identify molecular markers linked to the ALS resistance gene in G 10474. Three AFLP markers (E-ACA/M-CTT₃₃₀, E-AAC/M-CAG₃₁₀, and E-AAC/M-CAT₂₈₅) segregated in coupling phase with the resistance gene in G 10474. The E-ACA/M-CTT₃₃₀ marker was successfully converted to a codominant sequence characterized amplified region (SCAR) marker at 5 cM from the resistance gene. Validation of the SCAR marker outside the mapping population showed that the utility of this marker for marker-assisted selection (MAS) was limited to the Andean gene pool of P. vulgaris. Therefore, the SCAR marker we report can only be used to introgress the ALS resistance of G 10474 into Andean backgrounds.
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