Assessment of Harmattan weather on cowpea (Vigna unguiculata, (L.) Walp.) production under drought stress

Drought stress is an environmental factor which restraints crop production and quality worldwide. It is now undeniable that drought limits the performance of crop plants. Annual water resources decline due to low rainfall and the reduction of the number of days of rainfall. The objectives were to: (1) screen existing cowpea genotypes at germination and seedling stages for their adaptation to water stress and (2) identify tolerant cowpea varieties to drought. The experiments were carried out both in the laboratory using an osmotic stress (laboratory drought stress) induced by polyethylene glycol 6000 (PEG 6000) and in an open field under different levels (control, moderate and severe) of drought conditions. Fourteen Cowpea varieties were used in this study. The drought stress was imposed on 21-days old seedlings and the experiment lasted for 3 months. In the laboratory, four treatments 0%, 6.5%, 13% and 16.5% PEG were used while in the open field two drought levels were imposed. The two experiments were laid out in randomized complete block design with three replications. Morphological, physiological and agronomic data were collected. Results showed that at high concentration (16.50% PEG6000), high germination percentage was recorded in Raphael variety (88%) followed by Tawa (71.11%) and Eginwogogo (60%) whereas germination was completely inhibited in ITG7K-449-35 variety. The morphological traits measured such as plant height, leaf width, leaf length was reduced by drought stress. The highest reduction (47%) was recorded in the leaf width of Tiligre variety. In the second year of the experiment, IT99K-573-2-1 and Eginwogogo varieties plants died after 20 days of drought treatment because it could not withstand the drought stress condition during harmattan (a dry and dusty wind in West Africa) period due to the rapid dryness of soil moisture content. The results of dendrogram revealed that Raphael and Tawa were the most tolerant varieties