To explore the variations in symbiotic N 2 fixation and water use efficiency in cowpea, this study evaluated 25 USDA cowpea genotypes subjected to drought under field conditions at two locations (Kpachi and Woribogu) in the Northern region of Ghana. The 15 N and 13 C natural abundance techniques were respectively used to assess N 2 fixation and water use efficiency. The test genotypes elicited high symbiotic dependence in association with indigenous rhizobia, deriving between 55% and 98% of their N requirements from symbiosis. Consequently, the amounts of N-fixed by the genotypes showed remarkable variations, with values ranging from 37 kg•N-fixed•ha −1 to 337 kg•N-fixed•ha −1. Most genotypes elicited contrasting symbiotic performance between locations, a finding that highlights the effect of complex host/soil microbiome compatibility on the efficiency of the cowpea-rhizobia symbiosis. The test genotypes showed marked variations in water use efficiency, with most of the genotypes recording higher δ 13 C values when planted at Kpachi. Despite the high symbiotic dependence, the grain yield of the test cowpeas was low due to the imposed drought, and ranged from 56 kg/ha to 556 kg/ha at Kpachi, and 143 kg/ha to 748 kg/ha at Woribogu. The fact that some genotypes could grow and produce grain yields of 627-748 kg/ha under drought imposition is an important trait that could be tapped for further improvement of cowpea. These findings highlight the importance of the cowpea-rhizobia symbiosis and enhanced water relations in the crop's wider adaptation to adverse edaphoclimatic conditions.

Cowpea is multipurpose, leguminous, high protein crop in the tropics that provides food for humans and fodder for animals. The crop adds nitrogen and other nutrients to the soil through symbiotic relationship with rhizobia and direct decomposition of cowpea by-products. Despite its multiple benefits for humankind, the yield of cowpea is far below its potential and its production in the crop's birthplace of Africa is especially affected by abiotic factors. Soil moisture deficit is one of the main abiotic factors that affect the yield of cowpea in the semi-arid tropics, including the Sahelian and Guinea Savannah regions in West Africa. Even though cowpea is a drought tolerant legume, different genotypes respond differently to drought, resulting in up to 100% or more yield increases in the case of resistant genotypes or 50% or more yield loss in case of susceptible types. Mitigating the effect of soil moisture deficit on cowpea production requires selection of genotypes that can withstand drought. With this in mind, the goal of this study was to identify drought tolerant cowpea germplasm for the Savannah region of Northern Ghana using cultivated genotypes from the United States Department of Agriculture (USDA) tested with and without irrigation at the Bontanga irrigation facility during the dry season in 2018. Fifty genotypes were used, which included 45 imported from USDA and five (5) local genotypes from the Savannah Agriculture Research Institute (SARI). The experiment had 2 × 50 factorial treatments (irrigation × genotypes) and consisted of randomized complete block design with three (3) replications per treatment. Two (2) watering regimes were introduced namely, drought stressed (no irrigation) and non-stressed/control (irrigated). Morpho-physiological, phenological and yield data were taken on the cowpeas evaluated with drought tolerance as-How to cite this paper: Yahaya, D., Denwar, N. and Blair, M.W. (2019) Effects of Moisture Deficit on the Yield of Cowpea Genotypes in the Guinea Savannah of

Bambara groundnut (Vigna subterranea (L) Verdc.) is a leguminous plant that is widely cultivated in West Africa for its nutritious seeds. However, the hard-to-cook phenomenon of this legume affects its patronage by consumers. The quality and bioavailability of nutrients are affected by processing techniques during cooking. This study evaluated the effects of processing techniques on the nutritional quality of two Bambara groundnut varieties (namely, Simbi-bile and Sinkpili-zee). For this, each variety was subjected to four processing techniques, namely, (i) dehulled and soaked in water, (ii) dehulled and soaked in 1% NaHCO3 + 1% NaCl, (iii) dehulled and steamed, and (iv) Control. After sample processing, the Association of Official Agricultural Chemists (AOAC) standard protocols were used for chemical analysis. The results on proximate composition, anti-nutritional factors, and seed minerals composition showed significant variations among treatments. The main effects of variety and processing technique markedly influenced the parameters measured. Soaked Bambara groundnut with NaHCO3 reduced anti-nutritional factors. Steamed treatments yielded highest amount of protein (25.87%) while dehulled treated Bambara groundnut produced the highest amount of carbohydrate (42.77%). Calcium, potassium, and iron showed significant reduction (p ≤ 0.05) when dehulled. Additional sodium in processing Bambara increased mineral content of the crop. Anti-nutritional factor levels were also reduced significantly in simbi-bile when soaked. Proximate components (crude protein, crude fat, crude fiber, carbohydrate, and water) had significant changes in their compositions across all the processing techniques. From the correlation analysis, oxalate and phytate have some levels of effect in all varieties on every nutritional or mineral component. Total ash correlated negatively with crude fat and positively with phytate and oxalate. Dehulled and control did not reduce the anti-nutritional factors compared to NaHCO3 + NaCl. From the results, soaking of Bambara groundnuts in 1% NaHCO3 + 1% NaCl prior to cooking was effective in improving nutritional quality while overcoming the hard-to-cook phenomenon. The findings highlight the need to adopt correct processing techniques that conserve the nutritional benefits of these edible seeds. Soaking Bambara groundnut in NaHCO3 + NaCl as a processing technique increases mineral content while reducing anti-nutritional factors, and hence should be adapted.

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