Tafadzwanashe Mabhaudhi

The Potential Role of Neglected and Underutilised Crop Species as Future Crops under Water Scarce Conditions in Sub-Saharan Africa.

Modern agricultural systems that promote cultivation of a very limited number of crop species have relegated indigenous crops to the status of neglected and underutilised crop species (NUCS). The complex interactions of water scarcity associated with climate change and variability in sub-Saharan Africa (SSA), and population pressure require innovative strategies to address food insecurity and undernourishment. Current research efforts have identified NUCS as having potential to reduce food and nutrition insecurity, particularly for resource poor households in SSA. This is because of their adaptability to low input agricultural systems and nutritional composition. However, what is required to promote NUCS is scientific research including agronomy, breeding, post-harvest handling and value addition, and linking farmers to markets. Among the essential knowledge base is reliable information about water utilisation by NUCS with potential for commercialisation. This commentary identifies and characterises NUCS with agronomic potential in SSA, especially in the semi-arid areas taking into consideration inter alia: (i) what can grow under water-scarce conditions, (ii) water requirements, and (iii) water productivity. Several representative leafy vegetables, tuber crops, cereal crops and grain legumes were identified as fitting the NUCS category. Agro-biodiversity remains essential for sustainable agriculture.

Early establishment performance of local and hybrid maize under two water stress regimes

Maize (Zea mays L.) is the major grain crop in South Africa where most subsistence farmers still plant landraces. The objective of this study was to compare two landrace selections of maize with two hybrids popular among small-scale farmers in KwaZulu-Natal, for seed performance and water stress tolerance during seedling establishment. Two variations of a local landrace, white (Land A) and dark red (Land B), were compared to two hybrids, SC701 and SR52. Standard germination test and electrical conductivity were used to assess seed quality under laboratory conditions. Seedling emergence was performed in seedling trays using pine bark at 25% and 75% field capacity (FC), respectively, over a period of 21days. All seed types showed high germination capacity (>93%). There were highly significant differences (p<0.001) among seed types with respect to daily germination and germination velocity index (GVI). Landraces germinated slower than the hybrids. Landraces showed a 20% better root length and 41% lower electrolyte leakage than hybrids. There were differences (p<0.001) in seedling emergence between 25%FC and 75%FC. Hybrids showed better emergence at 75% FC. At 25% FC seedling emergence was drastically reduced (>5% in all varieties). Hybrids emerged faster than the landraces in both water regimes. Landraces performed better than hybrids under stress conditions. This study showed that landraces may have the same viability as hybrids and a better tolerance to stress during early establishment of the crop.

Growth, phenological and yield responses of a bambara groundnut (Vigna subterranea (L.) Verdc.) landrace to imposed water stress under field conditions

Bambara groundnut (Vigna subterranea (L.) Verdc.) is an underutilised species with potential to contribute nutritional and food security in marginal areas. Growth, phenology and yield of a local bambara groundnut landrace from Jozini, KwaZulu-Natal, characterised into three selections according to seed coat colour, namely Brown, Red and Light Brown, were evaluated under irrigated and rain-fed field conditions at Roodeplaat, Pretoria, over two seasons (2010/11 and 2011/12). Trials with three replicates were planted under rain-fed and irrigated conditions with seed colour as a subfactor. Emergence (up to 35 d after planting), plant height, leaf number, leaf area index, chlorophyll content index and stomatal conductance were measured in situ. Yield and components of yield were determined at harvest. The Red, Brown and Light Brown landrace selections emerged well (84%, 81% and 51%, respectively). Plant physiological and growth parameters of stomatal conductance, chlorophyll content index, plant height, leaf number, leaf area index and biomass accumulation were lower under rain-fed relative to irrigated conditions. Adaptations were landrace selection-specific, with the Brown and Red landrace selections showing better adaptation to rain-fed conditions. Under rain-fed conditions, bambara groundnut landrace selections flowered, senesced and matured earlier relative to irrigated conditions. Consequently, there were lower yields under rain-fed compared with irrigated conditions. The Red and Brown landrace selections may have drought-avoidance mechanisms. Seed colour may be used as a selection criterion for drought tolerance in bambara groundnut landraces.

Water-Food-Nutrition-Health Nexus: Linking Water to Improving Food, Nutrition and Health in Sub-Saharan Africa

Whereas sub-Saharan Africa’s (SSA) water scarcity, food, nutrition and health challenges are well-documented, efforts to address them have often been disconnected. Given that the region continues to be affected by poverty and food and nutrition insecurity at national and household levels, there is a need for a paradigm shift in order to effectively deliver on the twin challenges of food and nutrition security under conditions of water scarcity. There is a need to link water use in agriculture to achieve food and nutrition security outcomes for improved human health and well-being. Currently, there are no explicit linkages between water, agriculture, nutrition and health owing to uncoordinated efforts between agricultural and nutrition scientists. There is also a need to develop and promote the use of metrics that capture aspects of water, agriculture, food and nutrition. This review identified nutritional water productivity as a suitable index for measuring the impact of a water-food-nutrition-health nexus. Socio-economic factors are also considered as they influence food choices in rural communities. An argument for the need to utilise the region’s agrobiodiversity for addressing dietary quality and diversity was established. It is concluded that a model for improving nutrition and health of poor rural communities based on the water-food-nutrition-health nexus is possible.

Food and Nutrition Insecurity in Selected Rural Communities of KwaZulu-Natal, South Africa—Linking Human Nutrition and Agriculture

Lack of access to nutritious and balanced diets remains a major impediment to the health and well-being of people living in rural areas. The study utilizes a qualitative systematic approach to conduct an environmental scan and review of scientific literature of studies conducted in South Africa, specifically KwaZulu-Natal (KZN). Availability and access to nutritious, diverse and balanced diets were identified as key constraints for achieving food and nutrition security as well as for human health and well-being. This has led to both under- and over-nutrition, with the former, in particular stunting, affecting children under 5 years. A high incidence of over-nutrition, both overweight and obesity, was observed among black African females. In South Africa, poor people rely mostly on social grants and cannot afford a balanced diet. Under these circumstances, agriculture could be used to increase availability and access to diverse and nutritious foods for the attainment of a balanced diet. The wider use of traditional vegetable crops and pulses could improve availability and access to healthy and locally available alternatives. The promotion of household and community food gardens, and the use of nutrient dense crops with low levels of water use, i.e., high nutritional water productivity, offers prospects for addressing malnutrition in poor rural areas.

Influence of agro-ecological production areas on antioxidant activity, reducing sugar content, and selected phytonutrients of orange-fleshed sweet potato cultivars

Sweet potato is an important staple, and it is mainly known for its contribution of β-carotene in human diet. The effects of cultivar and habitat on this pigment and other nutritional characteristics of the crop still require investigation. In this study, three locally bred cultivars of sweet potato, two of which are orange-fleshed, were grown in three different agro-ecological areas to determine soluble sugar content, β-carotene, and total antioxidants of roots. In addition antioxidant activity, total carotenoids, and chlorophyll content were determined in edible leaves. Reducing sugars, β-carotene, total antioxidants capacity, total carotenoids, and chlorophyll content were significantly affected by environmental conditions. The location at lower altitude and closer to the coastline showed high evapotranspiration, thus reducing sugar content, antioxidant activity, and phytonutrients in both storage roots and leaves. Absence of water stress in agro-ecological locations further inland and at higher altitudes was associated with an increase in these compounds. Free radical scavenging activity of DPPH was higher in the storage roots (610.49 µmoles TE/100g) than in the leaves (426.06 µmoles TE/100g); nevertheless, opposite results were found for the ferric ion reducing activity (FRAP). The deep orange-fleshed cultivar A45 contained high β-carotene (15 mg/100g), which is enough to meet RDA for vitamin A. There is evidence of agro-ecological effect on sweet potato nutritional value.

DROUGHT TOLERANCE OF SELECTED SOUTH AFRICAN TARO ( COLOCASIA ESCULENTA L. SCHOTT) LANDRACES

Drought tolerance mechanisms of three taro landraces (Dumbe Lomfula (DL), KwaNgwanase (KW) and Umbumbulu (UM)) were evaluated under field conditions Pietermaritzburg, South Africa, over two summer seasons. Taro was slow to emerge (~ 49 days) and showed significant differences between landraces with respect to final emergence with DL never achieving a good crop stand. Growth (plant height, leaf number and LAI), VGI, SC and CCI were significantly lower under rainfed (RF) than irrigated conditions. RF conditions resulted in significantly lower biomass, HI, and final yield of taro landraces compared to irrigated conditions. The UM landrace avoided drought through increased stomatal regulation, lowering chlorophyll content, smaller canopy size and reduced growth period. It is concluded that among the three landraces, UM is suitable for production under water stress conditions, because it exhibited drought avoidance and escape mechanisms.

Perspective on crop modelling in the management of intercropping systems

The risk to food security is particularly dire in rural sub-Saharan Africa, where a third of the world’s undernourished people reside. Intercropping has the potential to improve rural livelihoods through better resource utilization and improved resilience to current and future challenges. This paper reviewed the concepts in intercropping and outlined how resources are captured and utilized within the system. Crop simulation models (CSMs) as decision support tools for intercrop/multicrop systems and future directions for modelling multicrop systems are the focus of the review. Through increased crop biodiversity, intercropping improves resilience, food security and nutrition. This is achieved through improved resource capture and utilization due to differences in spatial and temporal distribution of component crops. For farmers to maximize on these advantages, they need to have a thorough knowledge of species combination, arrangements and proportions. A major drawback to intercrop systems is that most of the existing agronomic recommendations are tailored on monoculture practices. This is also evident in the structure of most CSMs that cannot account for heterogeneous crop stands. In conclusion, there is a need to enhance agricultural research on intercrop systems, combining conventional and modern research approaches. Moreover, CSMs should be multidimensional in order to simulate system diversity accurately.

Growth, physiology and yield responses of Amaranthus cruentus, Corchorus olitorius and Vigna unguiculata to plant density under drip-irrigated commercial production

Amaranthus cruentus, Corchorus olitorius and Vigna unguiculata are traditional leafy vegetables with potential to improve nutritional security of vulnerable people. The promotion of these crops is partly hindered by the lack of agronomic information. The effect of plant spacing on growth, physiology and yield of these three leafy vegetables was evaluated under commercial-scale production at Roodeplaat, Pretoria over two summer seasons, 2011/12 and 2012/13. A randomised complete block design was used with plant density (100 000, 66 666 and 50 000 plants ha−1) as a factor. Chlorophyll content index (CCI), chlorophyll fluorescence, stomatal conductance, leaf number, leaf area index (LAI) and biomass were measured in situ. Planting at 100 000 plants ha−1 resulted in lower (P < 0.05) LAI, CCI and biomass per plant for A. cruentus and C. olitorius. Total yield of A. cruentus, C. olitorius and V. unguiculata was higher (P < 0.05) at 100 000 plants ha−1 relative to 50 000 and 66 666 plants ha−1. For A. cruentus and C. olitorius, higher leaf attributes (CCI, plant height, leaf number, biomass per plant and LAI) were obtained and this indicated that traditional leafy vegetables can be produced commercially under lower densities using a drip irrigation system. Using 66 666 plants ha−1 is suitable for commercial production of A. cruentus and C. olitorius, whereas 50 000 plants ha−1 may be recommended under low water availability. For V. unguiculata 100 000 plants ha−1 is recommended.

Seed quality and water use characteristics of maize landraces compared with selected commercial hybrids

Understanding seed quality and water use characteristics of maize (Zea mays L.) landraces will improve food security among subsistence farmers who still cultivate them. The objective of this study was to evaluate seed quality and water use characteristics of two maize landraces (GQ1 and GQ2) compared with two commercial hybrids (SC701 and PAN53). Seed quality was determined by the standard germination, electrical conductivity, and tetrazolium tests. A controlled environment study was conducted in which the landraces were compared with hybrids across three water treatments (30% ETc; 50% ETc, and 80% ETc). Although landrace GQ2 performed at par with the hybrids, overall, seed quality tests showed that hybrids had superior seed quality than landraces. This was also confirmed by highly significant emergence results (P < 0.001) from pot trials where SC701 and PAN53 had higher emergence (100% and 94.44%, respectively) compared with GQ2 (86.11%) and GQ1 (61.11%). Subjecting landraces and hybrids to water stress (50% and 30% ETc) resulted in shorter plants with fewer leaves and earlier tasselling compared with non-stressed plants (80% ETc). Plant height for the 30% ETc water treatment was 156.1 cm compared with 175.8 cm for the 80% ETc water treatment, while plants under the 30% ETc water treatment tasseled at 105.4 d compared with 129.5 d for the 80% ETc water treatment. The GQ2 landrace continued to perform similar to, and often better, than the hybrid varieties, especially under stress conditions. Yield was poor under controlled conditions. Performance of the GQ2 landrace for both seed quality tests and under controlled conditions shows that landraces remain an important germplasm resource.