Genetic Variability, Performance and Yield Potentials of Ten Varieties of Cowpea (Vigna unguiculata (L) Walp) under Drought Stress

Abstract

Food security is being threatening globally as a result of climate change and depletion of natural resources. Cowpea is one of the important crops that is needed to solve the world nutrition problem. Improvement for drought tolerance in cowpea can serve to mitigate the effect of drought stress resulted from climate change. Understanding the magnitude and type of genetic variability help the breeder to determine the selection criteria and breeding methods to be used for improvement purposes under drought stress. Ten cowpea genotypes were evaluated on the field during the dry season for two years in a RCBD (r=3) under well-watered (WW) and water-stressed (WS) environments. Data were collected on both morpho-physiological and agronomic characteristics. There was significant varying degree of reduction across the parental lines evaluated for all the characters. With respect to number of pods per plant, the highest reduction (64.8%) was observed in IT99K-513-21 and the lowest (-211.7%) in IT89KD-288; for number of seeds per pods, the highest (51.4%) in IT99K-513-21, the lowest (-2.7%) in TVU7778; for 100-seed weight, the highest (50.0%) in IT97K-499 and the lowest (-1.3%) in IT93K-432-1 and for total seed weight, the highest (82.8%) in IT92KD-357-3 and the lowest (-20.8%) in Danilla. The phenotypic and genotypic coefficient of variations were larger under WS than WW. Broad sense heritability estimates ranged between 12.3% in number of branches per plant to 99.0% for number of days to 50% ripe pods under WS. This genetic variability to drought stress provides opportunity for cowpea genetic improvement.

Production Constraints and Improvement Strategies of Cowpea (Vigna unguiculata L. Walp.) Genotypes for Drought Tolerance

“…Drought has been reported as a major constraint in semiarid tropics due to erratic rainfall in the beginning and towards the end of the rainy season [15]. e crop is usually subjected to drought stress in both seedling and terminal growth stages, and this causes substantial reduction in grain yield as well as biomass production.…”

“…us, there is a need for the establishment of effective breeding programs that can develop high-yielding and well-adapted varieties for water deficit conditions. Olajide et al [15] noted that drought is one of the most important abiotic constraints threatening food security in the world. is is because the livelihoods of African farmers depend on rain-fed agricultural systems that are seriously affected during periods of severe drought; thus, drought is a serious phenomenon in Africa [19].…”

Growth, biomass distribution, gas exchange and chlorophyll fluorescence in cowpea (Vigna unguiculata (L.) Walp.) under drought conditions

“…is one of the most important crops worldwide as it is part of the diet of millions of poor people in less developed tropical countries. Farmer families that cultivate this legume obtain a good income from the produced seed, especially the cream-colored cultivar with a black hilum (Olajide and Ilori, 2017). The seeds and fresh pods of this legume provide nutritional benefits, as they are rich in proteins, minerals (iron and zinc) and vitamins.…”

“…Their performance in environments where drought stress limits the survival of cultivars and production is also very important. Erratic rainfall due to climate change reduces cowpea grain yield (Olajide and Ilori, 2017) to such an extent that drought has caused relative reductions in yield from 0.38 up to 0.69, 57% in grain yield per plant, 49% in the number of pods per plant, and 32% of the number of seeds per pod (Cardona-Ayala et al, 2013). The adverse effects of water deficit are reflected in mineral nutrition and metabolism and lead to decreased leaf area, altered assimilates partition between organs (Merwad et al, 2018), decrease in plant height and in number of leaves per plant (Fahad et al, 2017).…”

“…Typically, new cultivars are obtained by selection during harvest and according to their components in specific environments without evaluating the effects of drought in different growth and development stages. Hence, it is necessary to complement the breeding strategy with the evaluation of new cultivars under prolonged drought conditions (Olajide and Ilori, 2017). In this way, phenotypic plasticity expressions of features associated with survival and drought resistance that could be used to select cultivars can be identified.…”