Abstract
Cowpea provides the cheapest source of protein with an average range of protein content of 23–30%. However, cowpea growth, development, and yield are greatly affected by drought during flowering and pod filling in the sub-Sahelian areas. The best way to cope with this situation is to develop drought-tolerant cowpea varieties. The objective of this study was therefore to evaluate cowpea lines developed through mutagenesis using gamma radiation to assess their reaction under optimal and water-stressed conditions. The response of ten mutants-irradiated Moussa local was then evaluated in pots arranged in a split plot design in a screen house. Two conditions were applied with optimum and water-stressed conditions. The stress was applied for two weeks at flowering. Two cowpea varieties Gorom local (drought-tolerant) and Moussa local (susceptible) nonirradiated were used as checks. Thereafter, field trials under two different sowing dates were conducted to identify the best tolerant mutant line(s) using agromorphological and tolerance indicators. The results indicated that mutant lines (MoussaM51-4P10 and MoussaM43-20P14) exhibited better stress tolerance and produced higher yield under water stress conditions. Stress Tolerance Index (STI) was better to select cowpea mutant tolerant with higher yielding under moderate stress (SI = 35%). The study confirmed that water stress has a negative effect on cowpea seeds production and on leaf chlorophyll content. The high temperature during experiment increased water stress effect mainly on non-irradiated checks (Gorom local and Moussa local).
Highlights
Cowpea (Vigna unguiculata) is grown throughout tropical and subtropical regions
22°C and 30° C [20]. e relative humidity means was 36.88% from 7 to 8:30 AM and it decreased to 20.69% from 1 to 2:30 PM. e lower value of relative humidity was observed after 1 PM. e result indicates that the environment condition was hot throughout the period of the experiment and the moisture was lower with high temperature. e study in [21] reported that high temperature in environment increased plant temperature implying high transpiration
Cowpea planting started in midJuly and it was harvested in September/October
Summary
Cowpea (Vigna unguiculata) is grown throughout tropical and subtropical regions. About 6.5 million metric tons of cowpea is produced annually on 14.5 million hectares in the world [1]. In sub-Saharan Africa, the first cowpea producers are Nigeria and Niger recording 80% of total production [1]. Burkina Faso stands third after Niger and Nigeria in West Africa group with 5.8 million metric tons of cowpea grains annually [2]. While in sub-Saharan Africa, cowpea yield remains one of the lowest among all grain legumes due to many constraints as the drought. In this region, rainfall comes late, is sparse, or stops earlier than usually required. Water deficit occurring during reproductive stage of cowpea plant limits cowpea growth and seed yield [6, 7] It induces significant alterations in plant physiology and biochemistry, reducing the water content of plant leaves and total chlorophyll. Most cowpea breeding programs for tolerance to drought used conventional breeding methods exploiting only the natural variability available. e selection within germplasm for a long time exhausted the genetic variability
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