This article is part of the Research Topic Food and Nutrition Security: Underutilized Plant and Animal-Based Foods
Source: Frontiers
March 2, 2023
Photo Source: Unsplash,
Rapid population growth, climate change, intensive monoculture farming, and resource depletion are among the challenges that threaten the increasingly vulnerable global agri-food system. Heavy reliance on a few major crops is also linked to a monotonous diet, poor dietary habits, and micronutrient deficiencies, which are often associated with diet-related diseases. Diversification—of both agricultural production systems and diet—is a practical and sustainable approach to address these challenges and to improve global food and nutritional security. This strategy is aligned with the recommendations from the EAT-Lancet report, which highlighted the urgent need for increased consumption of plant-based foods to sustain population and planetary health. Bambara groundnut (Vigna subterranea (L.) Verdc.), an underutilized African legume, has the potential to contribute to improved food and nutrition security, while providing solutions for environmental sustainability and equity in food availability and affordability.
This paper discusses the potential role of Bambara groundnut in diversifying agri-food systems and contributing to enhanced dietary and planetary sustainability, with emphasis on areas that span the value chain: from genetics, agroecology, nutrition, processing, and utilization, through to its socioeconomic potential. Bambara groundnut is a sustainable, low-cost source of complex carbohydrates, plant-based protein, unsaturated fatty acids, and essential minerals (magnesium, iron, zinc, and potassium), especially for those living in arid and semi-arid regions. As a legume, Bambara groundnut fixes atmospheric nitrogen to improve soil fertility. It is resilient to adverse environmental conditions and can yield on poor soil. Despite its impressive nutritional and agroecological profile, the potential of Bambara groundnut in improving the global food system is undermined by several factors, including resource limitation, knowledge gap, social stigma, and lack of policy incentives. Multiple research efforts to address these hurdles have led to a more promising outlook for Bambara groundnut; however, there is an urgent need to continue research to realize its full potential.
Introduction Eliminating hunger requires an adequate intake of energy and nutrients. Providing a healthy diet requires a food-based approach to improving diet and nourishing individuals. Despite the rich agrobiodiversity on Earth, humanity has evolved to rely on a few crops for nourishment. The last few decades have seen a global increase in the supply of dietary energy, through increased yield and production worldwide (1). However, this does not translate to the nutritional quality of the food we consume, nor does it ensure availability, accessibility, and affordability of food to vulnerable populations. The recent decades have seen an increase in prevalence of hunger, childhood overweight, and adult obesity (2).
Should we continue with our current production and consumption patterns, we are unlikely to achieve the UN Sustainable Development Goal (SDG) of Zero Hunger by 2030 (2). Factors such as population growth, urbanization, and changes in dietary pattern toward resource-intensive foods are driving the demand for increased food production (3). Pest and disease outbreaks, resource depletion, regional conflicts, and climate change are set to further undermine the capacity of the food system and exacerbate the situation (2, 3). To meet the SDG of zero hunger by 2030 and to end malnutrition in all its forms, the target is to increase the availability and accessibility to nutrients, not just calories. Adoption of a diversified healthy diet, with emphasis on affordable nutrient-rich plant-based foods such as fruits, vegetables, whole grains, and legumes can contribute to sustainable food and nutrition security (2, 4) and to the achievement of SDG2.
Bambara groundnut (Vigna subterranea (L.) Verdc) is a legume indigenous to Africa and is cultivated across the semi-arid sub-Saharan Africa region (5). It is a hardy crop and has been recognized as an important nutritious food source when food is scarce (6). This could be attributed to its climate-smart features, including its ability to fix nitrogen, and to grow under adverse environmental conditions such as poor soils and drought (7, 8). This nutrient-dense legume is sometimes termed a “complete food” due to its balanced macronutrient composition. Bambara groundnut contains ~64.4% carbohydrate, 23.6% protein, 6.5% fat, and 5.5% fiber and is rich in minerals (9). It is relatively underutilized compared with major cash crops and has often been associated with small-scale, subsistence farming, with women being the major producers and processors (6, 10). The utilization constraints of Bambara groundnut include the knowledge gap in improved seed system, agronomic practices, processing, and utilization. Genetics, agronomy, and nutritional aspects of Bambara groundnut and its food uses have recently been reviewed by other authors (7, 9, 11, 12). This paper gives an overview of the value chain and discusses the potential role of Bambara groundnut in closing the gaps in the food system to ensure sustainability of food and nutritional security.
Closing the Food Supply Gap Through Improved Production of Bambara Groundnut Bambara groundnut is thought to have its center of origin somewhere between West and Central Africa (13). It is grown widely in sub-Saharan Africa and is also present at low levels in Thailand, Malaysia, and Indonesia (7). Higher preference for Bambara groundnut has been observed in dry regions prone to drought (14). This is possibly linked to its ability to produce reasonable yields under such conditions, hence acting as a safety net for farmers. Bambara groundnut production in Africa is reported to be ~0.3 million tons annually with an average of 0.85 t/ha, although the yield potential is reported to be over 3 t/ha (5, 15). Nigeria is regarded as the largest producer of Bambara groundnut with a mean production of 0.1 million tons, followed by Burkina Faso 44,712 tons, and Niger 30,000 tons (5).
Genetic Diversity and Implications—Traditional Landraces vs. Modern Varieties Most germplasm planted by famers is in the form of landraces with high genetic variability. This is reflected by the wide variations in morphological (16) and nutritional (9) traits across Bambara groundnut landraces. Genetic variability can act as a form of insurance for farmers as some members of the landrace population can provide local adaptation, stress tolerance, and yield stability (17), thus giving farmers a higher chance of obtaining some form of seed yield in times of drought or other stresses.
High genetic variability observed in landraces also lends itself to high potential for crop improvement in Bambara groundnut. Most of the currently grown improved varieties of Bambara groundnut are generally landraces selected for improved yield, seed and flour quality, and drought tolerance (18). Bambara groundnut is usually sown as a minor crop, intercropped with other staples, by small holder African farmers for household consumption (5).
For this reason, coupled with low current market demand for the crop, yield stability is seen to be a more important aspect for landrace improvement than grain yield in order to ensure food security. Besides, the genetic diversity preserved in the gene pool allows some of these accessions to be developed into high protein and high oil cultivars (9), suggesting its potential in contributing to nutritional security in the region. Breeding improvement efforts of the promising landraces could consequently lead to improved profitability of the crop as well as adoption of the crop in diverse Bambara groundnut growing regions.
Productivity Traits and Agroecological Adaptation Variation in Bambara groundnut productivity has been attributed to agroecological factors, such as climate (19), soil fertility (20), water availability (21), and daylength (22). Nonetheless, it has been shown to exhibit adaptability across different regions under diverse growing conditions. For instance, the crop exhibits tolerance to soil acidity and low soil fertility (23), as well as adaptability to the tropical degraded acidic soils (24). Despite being classified as a facultative short-day crop for pod set (22), many landraces have adapted to regions with a broad range of daylengths. Physiological experiments have also revealed good recovery qualities when the crop is subjected to water stress (25).
Its yield is reported to be well above those of chickpea and similar to groundnut cultivars under comparable drought stress conditions (26, 27). This indicates that selection for drought tolerance is key considering that the crop is generally cultivated in arid to semi-arid regions of sub-Saharan Africa. Limited studies indicated that, although field drought conditions reduce the seed yield in Bambara groundnut, there is no effect on the nutritional quality of the seed (28). This trend has been observed in limited landraces and also in common bean (Phaseolus vulgaris L.) (29), but further studies on Bambara groundnut would be required to confirm this hypothesis.
Some areas where Bambara groundnut is grown have poor soils that are lacking in nitrogen. Most farmers in those regions do not apply synthetic fertilizers to their crops because the costs are often prohibitive (30). Bambara groundnut, as other nodulating legumes, can fix atmospheric nitrogen to replenish soil nitrogen, hence making it a potential companion crop for intercropping and rotational systems. It is often intercropped with cereals and root crops that can provide a significant amount of the calorie intake (31).
Its incorporation into crop rotation cycles can help to maintain soil fertility and break the cycles of pests and diseases, which is advantageous to resource poor farmers who might generally be unable to afford fertilizers and pesticides (32). Incorporation of Bambara groundnut in intercropping system with maize has been shown to increase the productivity of maize (33), indicating its potential contribution toward agrobiodiversity and subsequently food security. Varying rates and amount of nitrogen fixation have been observed for different Bambara groundnut accessions (24), and the enhancement of symbiotic nitrogen fixation was indicated to potentially increase its yield (34). The variability of nitrogen fixing capacity among Bambara groundnut landraces offers room for cultivar improvement and a positive correlation with yield would be an ideal scenario for the breeder.
Closing the Nutrient Gap Through Enhanced Utilization of Bambara Groundnut Bambara Groundnut as a “Complete Food” There is a growing trend toward increased consumption of plant-based diets, resulting in a need for more plant-based protein foods. Bambara groundnut is the obvious crop to consider. It serves as an important source of essential nutrients in areas where animal protein is scarce (35). The nutritional composition of Bambara groundnut has earned it the reputation of being a complete food.
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