Reaction of cowpea (Vigna unguiculata) cultivars to Striga gesnerioides races from Mali and Niger

Field, pot and laboratory experiments were performed to evaluate the resistance of 12 cowpea (Vigna unguiculata [L.] Walp.) accessions to two races of the parasitic weed Striga gesnerioides (Willd.) Vatke (witchweed) from Cinzana, Mali and Maradi, Niger. Cultivar IT82D-849 showed resistance to either S. gesnerioides race in field, pot and laboratory experiments. IT81D-994 and Suvita-2 were both resistant to S. gesnerioides from Cinzana, but were susceptible to S. gesnerioides from Maradi. The occurrence of distinct varietal specificity among S. gesnerioides races may indicate the existence of significant interpopulation genetic divergence. These results highlight the possibility that varietal resistance could be overcome by some races of the parasitic weed, emphasizing the necessity to perform cowpea selection for resistance to various S. gesnerioides races. Key words: Cowpea, parasite races, resistance, selection, Striga gesnerioides, varietal specificity