How to Improve Already Improved Cowpea—Terminal Drought

Cowpea (Vigna unguiculata) is a heat and drought resistant legume which thrives in poor and marginal soils, also due to its symbiosis with nitrogen fixing bacteria. Its high protein content suggests this crop fits perfectly with the three dimensions of sustainable development; social, economic and environmental issues. Extensive use of commercial varieties causes genetic variability loss, compromising breeding efforts in a context of climate changes. To contribute to the evaluation of Portuguese cowpea germplasm, several landraces were compared with a commercial variety (CV) in terms of productivity and physiological responses to drought. Potted plants were grown in a semi-controlled environment and well irrigated during the vegetative growth. Water stress was induced during the reproductive phase in half of the plants. Physiological measurements were conducted during stress. At the end of the cycle pods and seeds were counted and weighted. Despite a clear effect of stress in photosynthesis, there were no differences between the CV and landraces. However, under drought higher relative chlorophyll content (SPAD), was kept for a longer time in CV. Both the CV and landraces showed a marked decrease in productivity (60 - 70%) under stress. The induced drought had no impact on grains weight. As expected, the CV produced bigger and heavier seeds, eventually more appealing to consumers. Results suggest that CV and the studied landraces present a similar behaviour, reflecting the species adaptation to Mediterranean climate. Molecular characterization of genetic diversity is on course using microsatellites.