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

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 F, progeny f rom a cross of Tvx3236, a Striga-susceptible line, with IT82D-849, a resist ant cultivar, showed that resistance to S. gesnerioides race 1 from Burkina Faso was controlled by a single dominant gene, designated Rsg2-1. Three AF LP markers were identified that are tightly linked to Rsg2-1: E-AAC/M-CAA(3 00) (2.6 cM), E-ACT/M-CAA(524) (0.9 cM), and E-ACA/M-CAT(140/150) (0.9 cM), which appears to be codominant. Segregation analysis of a different F-2 po pulation resulting from a cross of the Striga-susceptible line IT84S-2246-4 with Tvu 14676, a S. gesnerioides race 3 resistant line, showed that resis tance to S. gesnerioides race 3 was also controlled by a single dominant ge ne, designated Rsg4-3. Six AFLP markers linked to Rsg4-3 were identified: E -ACA/M-CAG(120) (10.1 cM), E-AGC/M-CAT(80) (4.1 cM), E-ACA/M-CAT(150) (2.7 cM), E-AGC/M- CAT(150) (3.6 cM), E-AAC/M-CAA(300) (3.6 cM), and E-AGC/M-CAT (70) (5.1 cM). Segregation analysis of the EAAC/M-CAA(300) and E-ACA/M-CAG( 120) markers in recombinant inbred lines derived from IT84S-2049x524B deter mined that both are located within linkage group 1 of the cowpea genetic ma p. The identification of AFLP markers linked to Striga resistance provides a stepping stone for a marker-assisted selection program and the eventual c loning and characterization of the gene(s) encoding resistance to this noxi ous parasitic weed.