Cowpea is deemed as a food security crop due to its ability to produce significant yields under conditions where other staples fail. Its resilience in harsh environments; such as drought, heat and marginal soils; along with its nitrogen-fixing capabilities and suitability as livestock feed make cowpea a preferred choice in many farming systems across sub-Saharan Africa (SSA). Despite its importance, Cowpea yields in farmers’ fields remain suboptimal, primarily due to biotic and abiotic factors and the use of either unimproved varieties or improved varieties that are not well-suited to local conditions. Multi environment testing of genotypes is essential for recommending varieties suited for either specific or for wide cultivation. This study aimed, to identify and recommend cowpea breeding lines for wide or specific cultivation in the Sudan Savanna and Deciduous Forest zones of Ghana. The research utilized twenty early-maturing advance cowpea breeding lines and three check varieties (released varieties). The experiment was conducted in two locations: Bunso in the Deciduous Forest zone and Manga in the Sudan Savanna zone over 2020/2021 and 2021/2022 cropping seasons. Combined analysis of variance revealed a significant genotype-environment interaction (GEI) which accounted for 35.12% of the variation in yield. The environments were classified into three mega environments, with Bunso_2021 identified as the near-ideal environment where the genotypes exhibited their maximum genetic potentials. In terms of adaption, genotype UG_04 demonstrated broad adaption, showing high yield and stability across all test environments. Genotypes UG_01 and UG_02 performed particularly well in Bunso_2021 and Bunso_2022, while UG_04 and UG_14 excelled in Manga_2021. These findings provide valuable insights for selecting cowpea varieties that can enhance productivity and stability in diverse agro-ecological zones.

The cowpea aphid (Aphis cracivora) is a cosmopolitan insect pest that causes economic damage on cowpea. Although the pest persists at all the growth stages of the crop, in West Africa, aphids are the only major insect pests that farmers regularly control at the vegetative stage. Thus, deploying aphid-resistant crop varieties can reduce farmers' expenditure on insecticide. The availability of different biotypes of the pest and reports of resistance breakdown necessitates pyramiding of sources of aphid resistance to develop a more robust genotype for durable resistance. Two aphid-resistance genes, sourced from SARC-1-57-2 and IT97K-556-6, were introgressed through gene pyramiding technique into a farmers' preferred cowpea variety, Zaayura, using marker-assisted backcrossing. A simple sequence repeat (SSR) marker, CP 171F/172R, and an allele-specific single nucleotide polymorphism (SNP) marker, 1_0912, were used for foreground selection of the SARC-1-57-2 and IT97K-556-6 aphid resistance genes, respectively. A stepwise backcross approach was used to introgress the major aphid resistance QTL (QAc-vu7.1) from IT97K-556-6 into Zaayura using the marker 1_0912 coupled with intermittent screening under artificial aphid infestation. After the fourth backcross generation, three heterozygous BC₄F₁ of Zaayura/TT97K-556-6 were intercrossed to Zaayura Pali to develop intercross F₁ (ICF₁). Three true ICF₁ hybrids allowed to self to produce ICF₂. Five (5) out of 48 ICF₂ plants which were genotyped with the two foreground markers had the two aphid resistance genes fixed in the double homozygous dominant state. For background selection, out of 192 allele-specific markers screened, only 47 polymorphic markers were identified and used for the background analysis of the pyramided lines. The recurrent parent genome recovery ranged from 72 to 93.8 %. ICF₂_Zaa/556/SARC-P6 had the highest recurrent parent genome and the least heterozygosity among the five improved lines. The five pyramided lines showed superior resistance under artificial aphid infestation as compared to the two donor parents with damage scores ranging from 2.0 to 2.3. On the field, however, there were no significant differences between the pyramided lines and their recurrent parent for all the agronomic traits measured except for grain yield. The pyramided lines do not only stand the chance of being released as new varieties but are also valuable genetic resources for other breeding programs that seek to improve cowpea for aphid resistance.

Host plant resistance offers the cheapest, most sustainable and environmentally safe way to mitigate losses caused by the cowpea weevil, Callosobruchus maculatus (Fab.1775), in stored cowpea grains. This study aimed to identify cowpea cultivars that show resistance to infestation by C. maculatus during storage and the effect of its attack on seed germination. Sterilized grains of five cowpea varieties (Hansadua, Asontem, Tona, Wang‐kae, and Kirkhouse Benga) were placed in 500 mL kilner jars and infested with 48 h old C. maculatus . A completely randomized design was used. Data were collected on oviposition and hatchability rate, percent seed weight loss (PSWL), percent germination (PG) and percent seedling survival (PSS) as well as seed damage (SD). Dobie’s susceptibility index (DSI) was computed to determine the resistance of the genotypes to C. maculatus attack, while principal component analysis (PCA) was used to measure associations among variables contributing to resistance. The results showed that oviposition, hatchability and number of exit holes were low in Tona and Asontem. In contrast, these variables were high in Kirkhouse Benga and Hansadua. Percent germinability and PSS both declined by over 50% after 52 days of infestation. Also, the PCA showed that the first two principal components (PCs) accounted for 84.06% of the variance among the varieties with a positive association reported between DSI, oviposition, hatchability, number of exit holes and PSWL when they were used to generate a biplot. The variety Tona was considered tolerant while Asontem was classified as moderately resistant. Promotion of these less susceptible varieties could contribute to minimizing storage losses and deliver better returns to farmers and they can be used as sources of resistance in breeding programmes.