Variation in the virulence of Alectra vogelii populations on cowpea

Abstract

In glasshouse pot experiments 25 cowpea lines were exposed to samples of the parasitic weeds Alectra vogelii Benth., from several localities in West and Southern Africa, and Striga gesnerioides (Willd.) Vatke from Mali. The lines used were mainly those reported to have resistance to one or other parasite. No general cross‐resistance was observed and the resistance genes are assumed to be different for the two parasite species. Cowpea lines from Botswana, exposed to Botswana Alectra samples, showed responses ranging from complete resistance to susceptibility, in keeping with their reported behaviour in the field. All Botswana lines, however, showed almost complete resistance to Alectra samples from West Africa. It is concluded that there is an important difference between West and Southern African populations of A. vogelii. On the basis of these results it should be relatively easy to develop Alectra‐resistant cowpea varieties for use in West Africa.

Keywords:

• Crop resistance
• cowpea
• Alectra vogelii