Characterization of Virulence and Geographic Distribution of Striga gesnerioides on Cowpea in West Africa. J. A. Lane, Institute of Arable Crops Research-Long Ashton Research Station, Department of Agricultural Sciences, University of Bristol, Long Ashton, Bristol, BS18 9AF, UK. T. H. M. Moore, and D. V. Child, Institute of Arable Crops Research-Long Ashton Research Station, Department of Agricultural Sciences, University of Bristol, Long Ashton, Bristol, BS18 9AF, UK, and K. F. Cardwell, Plant Health Management Division, International Institute of Tropical Agriculture, Oyo Road, PMB 5320, Ibadan, Nigeria. Plant Dis 80:299. Accepted for publication 26 October 1995. Copyright 1996 The American Phytopathological Society. DOI: 10.1094/PD-80-0299.

A series of four cowpea cultivars (Blackeye, 58-57, IT81D-994, and B301) was used to differentiate the virulence of Striga gesnerioides from seven West African countries. Five parasite races were recognized, and their distribution across West Africa was mapped. Parasite samples that developed only on cowpea cv. Blackeye (race 1) were mostly from Burkina Faso, but also from Mali, Nigeria, and Togo. All other samples from Mali were pathogenic on c.vs. 58-57 and Blackeye (race 2). Striga gesnerioides from Niger and northern and eastern Nigeria was pathogenic on cvs. Blackeye, 58-57, and IT81D-994 (race 3). Race four of the parasite from southern Benin was pathogenic on cvs. Blackeye and B301. A fifth new race, pathogenic on cvs. IT81D-994 and Blackeye, was identified in parasite samples from Cameroon, Nigeria, Benin, and Burkina Faso. Additional sources of resistance against S. gesnerioides were sought in cowpea landraces. Six of 11 landraces tested were resistant to at least one race of S. gesnerioides