Differential and comparative screening of cowpea varieties to Striga gesnerioides (Willd.) Vatke for race specific identification in Burkina Faso

Significant efforts have been made to develop cowpea (Vigna unguiculata (L.) Walp.) varieties resistant to Striga gesnerioides in Burkina Faso. Despite these efforts, the resistant genotypes developed still express differential responses to Striga gesnerioides in different zones of the country. This suggests existence of intraspecific variability within the parasite. The objective of this study was to assess the intraspecific variability of cowpea genotypes to Striga gesnerioides infection in Burkina Faso. Ten cowpea varieties were screened over two consecutive years, under artificial infestation with 30 ecotypes of Striga seeds at Kamboinsé research station, in a screenhouse in Burkina Faso. Cowpea varieties used included Moussa local, Komsaré and KVx404-8-1, which are susceptible to all Striga ecotypes; and varieties B301, IT93K-693-2 and IT82D-849, which are free from all Striga ecotypes infestation. Cowpea varieties Tiligré, 524B, local Gorom and Niizwè had specific reactions depending on the ecotypes. The study highlights the existence of varietal specificities according to the geographical origin of Striga gesnerioides seeds. The structuring of the intraspecific diversity showed five biotypes, of which three were clearly identified as SG1, SG5 and SG Kp races; and two biotypes could not be identified. Although this study did not allow for a clear determination of the racial affiliation of the two new biotypes, it offers the possibility of developing new strategies to control Striga by focusing on the selection of resistant varieties based on regional specificities of Striga races in each agricultural zone.