Differential responses of 15 cowpea genotypes to three Striga hot spots in Niger

Abstract

Striga gesnerioides (Wild.) Vatke is the main biotic factor restricting yield of cowpea in Sub-Saharan Africa (SSA) in general and particularly in Niger. To date, seven  different races infesting cowpea have been identified in Africa based on differential responses of cowpea varieties. It was desirable to verify whether there are other Striga races a part from the race SG3 reported so far in Niger. Field and pots  experiments were conducted during two years in order to identify the different Striga races that infest cowpea in the country. Fifteen genotypes were screened under natural infestation in field as well as inoculated in pots with three samples of the parasitic weed collected in three hot spots. The test revealed Striga attack on three multiracial Striga resistant varieties: B301, IT97K-499-35 and IT98K-205-8 suggesting the presence of other races like SG4Z in the studied area, or the  breakdown of the resistance to Striga race SG3 in these cowpea varieties. Also, the resistance of HTR and Suvita 2 observed respectively in field at Kollo and in pots with Magaria sample suggested the prevalence of Striga race SG1 in these sites. From these observations, the geographical distribution of Striga races needs to be clarified in Niger and the extent to which two or more races can be associated in field requires further investigations.

Keywords: cowpea, Striga races, differential response, hot spots