CHARACTERIZATION OF VIRULENCE AND GEOGRAPHIC-DISTRIBUTION OF STRIGA GESNERIOIDES ON COWPEA IN WEST-AFRICA

A series of four cowpea cultivars (Blackeye, 58-57, IT81D-994, and B30 1) was used to differentiate the virulence of Striga gesnerioides from seven West African countries. Five parasite races were recognized, an d their distribution across West Africa was mapped. Parasite samples t hat developed only on cowpea cv. Blackeye (race 1) were mostly from Bu rkina Faso, but also from Mall, Nigeria, and Togo. All other samples f rom Mall were pathogenic on cvs. 58-57 and Blackeye (race 2). Striga g esnerioides from Niger and northern and eastern Nigeria was pathogenic on cvs. Blackeye, 58-57, and IT81D-994 (race 3). Race four of the par asite from southern Benin was pathogenic on cvs. Blackeye and B301. A fifth new race, pathogenic on cvs. IT81D-994 and Blackeye, was identif ied in parasite samples from Cameroon, Nigeria, Benin, and Burkina Fas o. Additional sources of resistance against S. gesnerioides were sough t in cowpea landraces. Six of 11 landraces tested were resistant to at least one race of S. gesnerioides.