Parasitism of cowpea by Striga gesnerioides: variation in virulence and discovery of a new source of host resistance

Summary In glasshouse experiments in the United Kingdom, Striga gesnerioides‐resistant cowpea varieties, Suvita‐2 and 58–57, were assessed alongside a susceptible variety for their responses to seventeen samples of S. gesnerioides from four West African countries. The susceptible variety was attacked by all samples, while Suvita‐2 was resistant to samples from Burkina Faso and Mali, and 58–57 was resistant only to samples from Burkina Faso. At least three physiological groups of the parasite can be distinguished: samples from Burkina Faso attacking the smallest range of cowpea varieties; those from Mali being intermediate; those from Niger and Nigeria attacking all the cowpea varieties. A sample from Cameroon behaved slightly differently and may represent a fourth type. A cowpea line from Botswana, B.301, selected for its field resistance to Alectra vogelii proved resistant to all Striga populations to which it was exposed, including those from Niger and Cameroon.