Genetic diversity and phylogenetic relationships among 141 cowpea (Vigna unguiculata L. Walp.) accessions collected throughout the nine geographical regions of Ghana were evaluated using simple sequence repeat (SSR) molecular markers. Twenty-five primer combinations pre-selected by their ability to polymerase chain reaction amplify SSRs from a set of test cowpea germplasm were evaluated. Of these, 20 primer combinations gave reproducible polymorphisms among 97.2% of the cowpea accessions tested, with the remaining accessions being found to be genetically identical. The informative primer combinations revealed a total of 74 alleles at 20 loci with an average of 3.8 alleles detected per locus. Variation in heterozygosity among cowpea SSRs ranged from 0.01 to 0.84 with an average occurrence of 0.19. The polymorphism information content varied from 0.07 to 0.66 with an average of 0.38. The Ghanaian cowpea accessions clustered into five main branches, each of which was loosely associated with the geographical regions from which samples were obtained. Accession GH2288 was found to be the most divergent cowpea accession compared with all others including the outgroup IT84S-2049, a breeding line from Nigeria. Our results provide a framework for future studies aimed at the conservation and management of cultivated cowpea germplasm in Ghana, and a good starting point for the selection of parental lines for genetic improvement programmes.

Cultivation of okra in Ghana is challenged by low yield due to lack of improved varieties. Gamma irradiated okra seeds can generate genetic variability to improve the crop. Samples of 150 seeds, each of okra genotype, UCCC6, were irradiated with 400 Gy to 1000 Gy using cobalt 60 source at a dose rate exposure of 121.58 Gy/hr. There were 40 stands comprising single plant per stand in three replications per treatment in a randomized complete block design outlay. Seedling survival, plant height, number of leaves, stem diameter, number of branches, leaf length and width, days to 50% flowering, number of fruits, length and weight of fruit, number of seeds, and 100-seed weight decreased significantly ( ≤ 0.05) with increasing doses of gamma rays. Seedling survival was highest (88%) at 400 Gy, followed by control (81%). However, 600 Gy, 800 Gy, and 1000 Gy had 61%, 41%, and 17% seedling survival, respectively, with LD 50 at 720 Gy. Significant ( ≤ 0.05) correlations existed between growth and yield components. Optimum growth and yield in okra were induced by 400 Gy but the higher doses had growth retardation effects and the induced variability can be assessed at M 2 generation.

The effect of biochar alone or co-applied with triple superphosphate on rhizosphere soil characteristics, nodule formation, phytoconstituents and antioxidant property of cowpea ( Vigna uguiculata ) is yet to be adequately examined in sub Saharan Africa. A field experiment was conducted where cowpea ( Vigna unguiculata ) was grown in a tropical sandy loam soil amended with biochar at 1.5 t ha −1 and 2.5 t ha −1 solely or together with inorganic phosphate fertilizer (Triple superphosphate), applied at a rate of 60 kg P ha −1 . At 50% flowering, changes in selected rhizosphere soil properties (pH, total nitrogen, available phosphorus, soil organic carbon, cation exchange capacity), nodule count, phytochemicals (phenols, flavonoids, alkaloids, tannins, saponins) and antioxidant property of cowpea roots and leaves were determined by standard laboratory procedures. Differences between means of the measured parameters were established using ANOVA, and relationships among the parameters were explored using Pearson correlation (p < 0.05). Addition of biochar solely or in combination with TSP significantly (p < 0.05) increased soil pH, total nitrogen, available phosphorus, soil organic carbon, cation exchange capacity and root nodule count. Flavonoids, phenols, alkaloids, saponin, tannin contents and antioxidant activity in the roots and leaves were significantly (p < 0.05) higher in the amended soils compared with the unamended soil. Similarly, soil flavonoids, phenols, alkaloids and antioxidant activity were significantly higher in amended soils compared with control. Significant, positive inter and intra correlation with varying strength was found between soil properties, nodule number and phytoconstituents. This is an indication that biochar can be co-applied with triple superphosphate to sustain soil fertility, improve nodulation and enhance concentrations of phytoconstituents in soil, cowpea roots and leaves.

Cowpea [Vigna unguiculata(L.) Walp] is an important food security crop in Sub-Saharan Africa. However, cowpea production in some parts of this region is constrained byStriga gesnerioides(Willd.) Vatke infestation resulting in yield losses. This study assessed the farmers and agricultural extension officers (AEOs) perception ofS. gesnerioidesparasitism on cowpea in the Upper East Region of Ghana. In all, 200 respondents—179 cowpea farmers and 21 AEOs—in five cowpea growing districts were randomly sampled to answer closed- and opened-ended questions coupled with visit to cowpea farms. Majority of the farmer respondents were males between the ages of 21 and 60 with very little or no formal education. Almost all of the respondents could identify the parasitic weed,S. gesnerioides,but they lacked adequate knowledge of the parasitic effects on the host, cowpea plant.S. gesnerioidesinfestation was widespread and devastating in almost all the fields surveyed. Its effects on the host plants (cowpea) included stunted growth, leaf senescence, chlorosis, death of the crop, and reduced yield. Different management strategies employed by the farmers to contain the spread of the parasite include weeding (90%), application of manure (5.5%), and crop rotation and fallowing (4.0%). Both farmers and extension officers had very little knowledge on existence ofS. gesnerioidesresistant cowpea genotypes for cultivation. Farmers expressed the desire to cultivateStriga-resistant cowpea varieties when made accessible, since it is the most reliable and environmentally friendly method of controlling the parasitic weed.