Identification of AFLP markers linked to resistance of cowpea (Vigna unguiculata L.) to parasitism by Striga gesnerioides

Abstract 

AFLP and bulked segregant analysis were used to identify molecular markers linked to resistance of cowpea [Vigna ungiculata (L.) Walp.] to parasitism by Striga gesnerioides (Willd.) Vatke. Segregation analysis of F₂ progeny from a cross of Tvx3236, a Striga-susceptible line, with IT82D-849, a resistant cultivar, showed that resistance to S. gesnerioides race 1 from Burkina Faso was controlled by a single dominant gene, designated Rsg2–1. Three AFLP markers were identified that are tightly linked to Rsg2–1: E-AAC/M-CAA₃₀₀ (2.6 cM), E-ACT/M-CAA₅₂₄ (0.9 cM), and E-ACA/M-CAT_140/150 (0.9 cM), which appears to be codominant. Segregation analysis of a different F₂ population resulting from a cross of the Striga-susceptible line IT84S-2246–4 with Tvu 14676, a S. gesnerioides race 3 resistant line, showed that resistance to S. gesnerioides race 3 was also controlled by a single dominant gene, designated Rsg4–3. Six AFLP markers linked to Rsg4–3 were identified: E-ACA/M-CAG₁₂₀ (10.1 cM), E-AGC/M-CAT₈₀ (4.1 cM), E-ACA/M-CAT₁₅₀ (2.7 cM), E-AGC/M-CAT₁₅₀ (3.6 cM), E-AAC/M-CAA₃₀₀ (3.6 cM), and E-AGC/M-CAT₇₀ (5.1 cM). Segregation analysis of the E-AAC/M-CAA₃₀₀ and E-ACA/M-CAG₁₂₀ markers in recombinant inbred lines derived from IT84S-2049×524B determined that both are located within linkage group 1 of the cowpea genetic map. The identification of AFLP markers linked to Striga resistance provides a stepping stone for a marker-assisted selection program and the eventual cloning and characterization of the gene(s) encoding resistance to this noxious parasitic weed.