The continued improvement in the yield of cowpea for the semi-arid regions where it is a dominant crop will record rapid progress if the genetic basis for yield under different moisture regimes is better understood. This study investigated the genetic combining abilities and heterosis for grain yield, yield components, flowering and biomass production among diallel hybrids derived from nine cowpea genotypes. Results showed that moisture stress significantly reduced grain yield, biomass production, and number of pods per plant. Only for grain yield was a significant interaction observed for moisture regimes. Genetic control for grain size, number of seeds per pod and days to flowering was dominated by additive genetic effects. For grain yield, both additive and non-additive genetic effects were dominant. The genetic control of yield under the two soil moisture conditions indicated that grain yield improvement will be more challenging for drought prone regions. Nonetheless, careful selection of genotypes that have complementary but different alleles for yield under different soil moisture conditions might permit yield improvement through recurrent selection. This study has identified parental lines, developed populations, and provided a breeding strategy for developing cowpea cultivars with higher grain yield for Guinea and Sudan savannah regions of West Africa.

No abstract

A B S T R A C TPlant breeders' efforts in developing drought tolerant and high-yielding cowpea varieties may be in vain unless the developed varieties are evaluated to ascertain the influence of water stress on their nutritive value, antioxidants, and phenolic contents under contrasting moisture regimes. The study was set up to evaluate the nutritional value, phytochemical content and antioxidant activity of cowpea Recombinant Inbred Lines (RILs) under contrasting soil moisture in the Guinea and Sudan Savanna agro-ecologies of Ghana. Forty-eight cowpea RILs seed samples from well-watered and water stress experiment were pulverized. Distillation and titration was carried out and the organic samples extracted and various biochemical analyses were carried out using standard protocols and methodologies. The dried grain mineral contents were determined using an Atomic Absorption Spectrophotometer, while the protein content was determined by the combustion method. Correlation and regression analysis and principal component analysis were performed using STATA version 13. Biochemical analysis for seed related traits revealed that inbred lines responded differently to drought. Significant differences of watering regimes on various phytochemical traits were only observed in phosphorus and lead. Inbred line with family number 57 had the highest crude protein content of 46.90% under well-watered conditions. Inbred line 84 under water stress conditions had high levels of Mg and K. Inbred line 20 under well-watered conditions had the highest antioxidant content. For phenolic acid content, inbred line 255 scored the highest. Quercetin and rutin were most abundant in inbred line 186 for both water-stress and well-watered conditions. The indication is that moisture stress could affect seed yield but no effects on the phytochemical and nutritional variables. Genotypic differences could arise from parental combination used for developing the inbred lines for the study.

The use of multiple traits for drought study affirms the complexity of drought tolerance in cowpea. Despite the availability of several traits for drought tolerance evaluation, the rapid screening technique used by many scientists for seedling drought in wooden boxes is the simplest method for screening large populations. The objective of this study was to select drought tolerant cowpea recombinant lines developed from a drought tolerant and susceptible parent using the wooden box screening technique. Two hundred Recombinant Inbred Lines (RILS) an F 2 : 6 generation were used for the study. The parents were drought tolerant line crossed with susceptible line. Screening was done in wooden boxes and plants stressed for 4 weeks and in two sessions. Leaf wilting, relative water content, chlorophyll content during stress, and recovery from drought data were taken. Results from this study showed significant differences (p < 0.05) for relative chlorophyll content for the 4 weeks of water stress and relative water content taken on the second week of water stress for all 200 inbred lines, but no significant differences were observed for the parental checks. Relative water contents taken for RILS during water-stress ranged between 70-20% for drought tolerant and drought susceptible lines respectively. The parental lines used as checks both had relative water contents of 60%. Relative water content for the second experiment ranged between 74-22% for tolerant and susceptible RILS respectively. About 12 inbred lines consistently performed well for recovery, 13 RILS were susceptible. RILS that maintained a higher relative water and chlorophyll contents, with high proportion of survived seedlings were 11. Potential seedling drought tolerant RILS have been identified.

Background: Cowpea plays a critical role in the lives of millions of people in Africa and other parts of the developing world, where it is a major source of dietary protein that nutritionally complements staple low-protein cereal and tuber crops. It is a valuable and dependable commodity that produces income for farmers and traders. Objective: To review related research work on the genetic variability for time to flowering, maturity and drought tolerance in cowpea. Data Source: Searches were made from the following databases and archives; International Institute of Tropical Agriculture (IITA), The Essential Electronic Agricultural Library (TEAL), Access to Global Online Research in Agriculture (AGORA) (FAO), AGRICOLA (National Agricultural Library), AGRIS - Agricultural Sciences and Technology (FAO), CAS - Chemical Abstracts (ACS), DOAJ - Directory of Open Access Journals, CABI, Euphytica, Elsevier, Research Alert, Scopus and CGIAR, Plant Genetics and Breeding Database, Crop Science Database, Plant Genetics and Breeding Database, data base repositories, using the terms “genetic variability”, “drought”, “tolerance”, “ time to flowering and maturity”, and “cowpea” individually or in combination to identify literature published in English language between January 1990 to January 2018. Methods: The review was carried out using the above search terms. Research papers were critically reviewed, relevant data extracted, and a narrative synthesis was conducted to determine the relevant papers. Results: In all 150 papers met the inclusion criteria. Collections were from varied background; Sub-Saharan Africa, Asia, Europe, and Latin Americas. Conclusion: Despite research studies on cowpea and drought, there appears to be limited such research findings on the time to flowering, and maturity in relations to drought tolerance in cowpea in Ghana, suggesting more research in this part of the world.