REACTION OF COWPEA (VIGNA-UNGUICULATA) CULTIVARS TO STRIGA-GESNERIOIDES RACES FROM MALI AND NIGER

Field, pot and laboratory experiments were performed to evaluate the r esistance of 12 cowpea (Vigna unguiculata [L.] Walp.) accessions to tw o races of the parasitic weed Striga gesnerioides (Willd.) Vatke (witc hweed) from Cinzana, Mall and Maradi, Niger. Cultivar IT82D-849 showed resistance to either S. gesnerioides race in field, pot and laborator y experiments. IT81D-994 and Suvita-2 were both resistant to S, gesner ioides from Cinzana, but were susceptible to S. gesnerioides from Mara di. The occurrence of distinct varietal specificity among S. gesnerioi des races may indicate the existence of significant interpopulation ge netic divergence. These results highlight the possibility that varieta l resistance could be overcome by some races of the parasitic weed, em phasizing the necessity to perform cowpea selection for resistance to various S. gesnerioides races.