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Genetic diversity is crucial for crop improvement in any breeding program. Cowpea is an important indigenous grain vegetable legume crop. The crop has a significant potential to improve food and nutritional security in sub-Saharan Africa (SSA), and family income for resource poor famers. Cowpea is a source of proteins, vitamins (folate, thiamine and vitamin C), minerals (Fe, Zn, Mn and Ca) and amino acids such as lysine and tryptophan, hence, has a high potential for combating nutrient deficiencies. The SSA countries, including South Africa, have been experiencing many dry seasons, which have negatively affected agricultural production and productivity. Cowpea has a long taproot with the ability to grow in arid and semi-arid regions; however, lasting exposure to severe droughts will result in significant yield and grain quality reduction. There has been limited progress in drought tolerance research in cowpea due to the complexity of this trait, as it involves numerous genes, which in turn are affected by environmental conditions. It is therefore important to review research done on the nutritional, phenotypic and genotypic diversity of cowpea and the importance of diversity when breeding for complex quantitative traits such as drought tolerance and yield. The review will also outline the important omics tools used for drought tolerance breeding, cultivar development and as reference for future cowpea breeding. Cowpea is a highly nutrient-dense, underutilised orphan legume crop with high potential to address malnutrition and food security in the world. Cowpea crop can withstand drought and high-temperature conditions, however, lasting exposure to severe droughts will result in significant yield reduction and poor grain quality. Thus, understanding the variation present in the available cowpea accessions will assist in breeding superior cowpea varieties that can withstand the ever-changing climate. [ABSTRACT FROM AUTHOR]

Correlations and path coefficient analysis provide knowledge on trait interrelationships and potential for simultaneous, direct, or indirect selection in plant breeding. The objective of this study was to determine the genetic and phenotypic correlations as well as the path coefficient analysis among grain yield components and nutritional quality traits in cowpea genotypes. Data for grain yield components and mineral elements were collected from 70 cowpea genotypes planted at two environments in 2017/18 and 2018/19 seasons in South Africa. Grain yield had significant (P <0.05) positive phenotypic correlations with number of seeds per pod (SPP), indicating that selection of cowpea genotypes based on SPP could be effective in maximizing grain yield. The heat map showed that grain yield was strongly associated with number of branches (NB), SPP and number of pods per plant. Among the yield components, only SPP showed significant (P <0.05) positive phenotypic correlations with Zn, Mn, and Mg. Grain yield showed no genetic correlations with yield components and nutritional quality traits. Significant (P <0.05) positive genetic correlations were observed between yield components and most of the nutritional quality traits, indicating inherent association among the traits. Path coefficient analysis identified SPP and NB as major contributors to grain yield. The PCA identified cowpea genotypes such as ARC030, ARC011, ARC016, ARC024, NGOII, ARC032, IT90K59, and ARC047 with high grain yield and good nutritional quality traits that can be used further as potential parents for crop improvement through biofortification. The clustered heat map distingished five groups of cowpea genotypes and three of those were associated with good grain yield and nutritional quality traits which could make cowpea a good choice to combat food security and malnutrition in the world. [Display omitted] • Genetic and phenotypic correlations as well as the path coefficient analysis among grain yield components and nutritional quality traits in cowpea genotypes were determined. • Correlations and path coefficient analysis provide knowledge on trait interrelationships and potential for simultaneous, direct, or indirect selection in plant breeding. • Grain yield had significant positive phenotypic correlations with number of seeds per pod, indicating that selection of cowpea genotypes based on SPP could be effective in maximizing grain yield. • Seed pods per plant showed positive phenotypic correlations with Zn, Mn, and Mg. • Path coefficient analysis identified seed per pod and branches per plant as major contributors to grain yield in cowpea. [ABSTRACT FROM AUTHOR]

• Cowpea is a highly valued fruit and leafy vegetable crop contributing to food, nutrition, and health security. • Low cowpea production and productivity in sub-Saharan Africa and globally are due to a lack of improved cultivars with multiple disease, and insect pest resistance and drought tolerant; moreover, there is a lack of seed system research in cowpea. • The extensive phenotypic and genotypic variation found in cowpea genetic resources is useful for the development of cultivars with enhanced grain yield, leafy yield and nutritional values as well as drought tolerant. Despite the contribution of cowpeas to food security and the crop's numerous nutritional and health attributes, consumers in South Africa have labelled cowpeas, among other leguminous crops as a "poor people's food" ; this contributed to the gradual decline in the cultivation and use of the crop. This, in turn, resulted in the observed high reliance on limited number of plant based protein crops and excessive consumption of livestock products. In this paper, three aspects are interrogated, i.e., genetic resource management, production constraints as well as the trade performance and consumption of cowpeas in South Africa. A clear understanding of these aspects renders an informed decision upon which recommendations for the necessary practical interventions that are needed to be put in place to spur the development of target products and cowpea's value chain. The assessment of genetic resource management and seed production constraints of cowpeas was based on a review of relevant literature, while descriptive analysis of secondary data spanning a period of 10 years (2010-2019) obtained from Trade Map and FAOSTAT databases was used to interrogate the trade performance and consumption of cowpeas. Findings reveal that seed production constraints are largely anchored on the limited attention government and policy making institutions have accorded to the seed system of orphaned crops, thereby compromising their potential by failing to supply affordable good quality seeds to smallholder and commercial farmers. However, South Africa has one of the largest and most diverse collections of cowpea germplasm housed at the Agricultural Research Council. With regard to trade performance and consumption, results show that South Africa is a net exporter of cowpeas, with a 10 years' period annual average worth R2.9 million. Given that South Africa does not re-export cowpeas, yet on average 4848 tonnes are produced annually, it is a clear indication that the country produces lightly more than what is consumed domestically – on average 4634 tonnes per annum. Therefore, recommendation is made to bolster cowpea production and productivity through mainstreaming the legume seed system towards boosting local and export markets as well as strongly enhancing local consumption by creating awareness of the nutritional and health benefits of cowpeas. Furthermore, there is a need to increase awareness about the nutritional and health benefits of cowpeas and other leguminous crops, among other socio-economic benefits. This is important in spurring cowpeas consumption domestically, while countering the over reliance on animal products as protein sources and the associated risks such as such as high greenhouse gas emissions and obesity for people. [ABSTRACT FROM AUTHOR]

The identification of high-yielding and stable genotypes for cultivation across differential production regions is among the key breeding objectives in cowpea improvement programs. This study was aimed to determine genotype-by-environment interaction (GEI) for grain yield to select high-yielding and stable cowpea genotypes for production in South Africa and identical agro-ecologies, and for cultivar development. Fifty cowpea genotypes were tested for grain yield across seven environments of South Africa using a 10 × 5 alpha lattice design replicated three times, during the 2019/2020 and 2020/2021 planting seasons. Grain yield data were subjected to analysis of variance (ANOVA), additive main effects and multiplicative interaction (AMMI) and the genotype-by-environment interaction (GGE) biplot analyses. ANOVA and AMMI showed significant genotype, environment and GEI effects. High grain yield was recorded for genotypes G35 (0.47 t ha−1), G1 (0.45 t ha−1) and G47 (0.43 t ha−1) across test environments. AMMI stability values (ASV); identified Acc-Cowp44 as the most stable genotype across all sites, recording the lowest ASV of 0.03. The comparison view of GGE biplot revealed Acc-Cowp29, Acc-Cowp38 and Acc-Cowp5 as ideal genotypes, possessing high grain yield of 0.19, 0.47 and 0.36 t ha−1, respectively. The identified genotypes are recommended for production and inclusion in subsequent breeding activities. [ABSTRACT FROM AUTHOR]

Cowpea is an important food and nutritional security grain legume crop in the semi-arid regions of sub-Saharan Africa. Its production is limited by biotic factors including pre-harvest insect pests such as aphids. Aphids cause yield reductions, promotes the growth of sooty moulds, honeydew and as a result reduce photosynthetic processes and rates. Various methods have been deployed to try to control the damage of aphids in cowpea plants. The methods include the use of chemical insecticides, cultural, mechanical, biological controls and integrated pest management. However, these methods have not been very effective as smallholder farmers growing cowpea in marginal areas cannot afford them. Hence, host plant resistance/genetic control is the best and effective method for controlling aphids in cowpea plantations. Breeding for aphid resistance is one of the effective methods that can sustain the production and productivity of the cowpea for longer periods. Furthermore, assessing the presence of genetic diversity can also help in sourcing genes of novelty for addressing this important issue to increase the production and productivity of the crop. Recently, scientists have used various strategies to try to solve the challenge of aphid damage on cowpea. The objective of this review was to document the research progresses on aphid resistance breeding of cowpea to facilitate the breeding and conservation of cowpea germplasm. The review serves as a baseline information to guide future cowpea breeding for resistance to aphids. [ABSTRACT FROM AUTHOR]