Albert T. Modi

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.

WHEAT SEED QUALITY IN RESPONSE TO MOLYBDENUM AND PHOSPHORUS

ABSTRACT Similarity of the molybdate and phosphate anions suggests that these nutrients are likely to interact in plant metabolism. This relationship has not been explained with respect to seed quality. The objective of this study was to examine wheat (Triticum aestivum L.) seed quality in response to varying nutrient solution concentrations of molybdenum (Mo) and phosphorus (P). Seeds of wheat, cultivar Tugela DN, were produced in pots under controlled environmental conditions. Plants were watered twice a week with a modified Hoaglands nutrient solution containing no Mo and 10 mg L−1 P, supplied from a separate source, as a control. Separate Mo (1.8, 3.6, and 5.4 mg L−1) and P (10, 20, and 30 mg L−1) treatments were also applied simultaneously as the Hoaglands solution to plants from one week after pre-germination in a growth chamber to seed maturity. Seed yield, germination, α-amylase activity and total protein concentration were determined in seeds harvested at a moisture content of about 12%. Results showed that P did not affect Mo suppression of α-amylase activity, but there was a negative interaction between Mo and P with respect to seed germination. Both Mo and P increased seed protein content, seed yield and seedling vigor. These data suggest that while P fertilization contradicts the induction of seed dormancy by Mo, this interaction does not negate the reduction of late maturity α-amylase activity by Mo. Since late maturity α-amylase reduction is the major goal of pre-harvest sprouting alleviation, these data could be useful in providing an agronomic tool to alleviate pre-harvest sprouting while simultaneously enhancing wheat seed vigor.

Molybdenum deficiency in wheat results in lower dormancy levels via reduced ABA

Wheat which was grown in acid-washed sand and irrigated with a molybdenum-free nutrient solution was treated with various concentrations of molybdenum (Mo) as a foliar spray at the flag leaf stage. At maturity, dormancy levels and abscisic acid (ABA) content of the seed were determined. Seed dormancy and ABA content increased with increasing rates of Mo application. In a field experiment, wheat (cv. SST 66) was treated with 100 ppm Mo by foliar application at the flag leaf stage. Embryos were tested for sensitivity to exogenously applied ABA. Embryos from Mo-treated plants showed enhanced sensitivity to ABA-induced inhibition of germination. The Mo application also resulted in significantly higher levels of endogenous ABA and Mo in the seeds. It is postulated that Mo deficiency leads to a lack of dormancy in wheat via reduced synthesis of ABA.

Temperature and light requirements for the germination of Cleome gynandra seeds

Seeds of Cleome (Cleome gynandra L.) are characterised by low germination and may require after-ripening. The dormancy characteristics and optimum conditions for seed germination of this species have not been explained. The objective of this study was to investigate the effects of temperature, light and pre-germination treatments (chilling, scarification, hydration and germination in the presence of KNO3 or GA3) on the germination of Cleome seeds. Seeds were germinated for 10 days and the final count of germination was used to determine seed performance. The highest germination percentage (60% and 80%, for a 2-year old and a 1-year old seed lot, respectively) of untreated seeds was achieved when alternating temperatures of 20–30°C (16 h—8 h) in the dark or constant 30°C in the dark were used. Among the pre-germination treatments, only scarification (puncturing of seeds at the radicle end) improved germination. Seeds were found to be negatively photoblastic, and the phenomenon was more pronounced when the germination test was undertaken at 20°C and at light exposures of 12 h day−1 or longer. Germination of photo-inhibited seeds was, however, improved by treatment with GA3. It is recommended that the germination of Cleome should be performed under conditions of darkness and either alternating 20–30°C or continuous 30°C.

Response of local mustard germplasm to water stress

A preliminary study was conducted to compare three wild mustard (Brassica species) landraces with respect to germination capacity and seedling emergence under two water regimes. Seeds of three landraces [Isaha, Masihlal-isane (both Brassica juncea (L.) Czern & Coss) and Kway-imba (Brassica nigra (L.) W.D.J. Koch)] were characterised according to seed colour: black, brown, grey, greyish-black and reddish-brown. Seed quality was determined by germination test and seedling establishment in response to two water regimes [25% and 75% field capacity (FC)]. There were highly significant (P < 0.001) effects of landrace and seed colour with respect to germination capacity. Masihlalisane showed 99–100% germination for brown, grey and black seeds. For Isaha brown seeds displayed 85% germination, grayish-black seeds showed 95% germination and reddish-brown seeds showed 82% germination. Kwayimba showed the least germination capacity, and black seeds were the most dormant (close to 0% germination). Brown seeds of Kwayimba had 14% germination and reddish-brown seeds showed 22% germination. There was no significant effect of seed colour on seedling establishment. Seedling establishment under 25% FC was ˜45% for Isaha and Masihlalisane, and Kwayimba did not emerge. At 75% FC, there was ˜80% emergence for all landraces. However, by the end of the experiment (21 days after emergence) only seedlings grown under 75% FC were harvestable and the darker the seeds the better was the biomass (P < 0.01). It is concluded that water stress tolerance in wild mustard maybe associated with the trait of seed colour.

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.

Effect of indigenous storage method on performance of taro [Colocasia esculenta (L.) Schott] under field conditions in a warm subtropical area

Successful crop stand establishment, a critical prerequisite for efficient crop production, is primarily determined by propagule quality. Taro [Colocasia esculenta (L.) Schott] corms of different sizes (80–100 g corm−1, 40–60 g corm−1 and 20–30 g corm−1) that had been stored in soil pits at different depths (10, 20, 30,40 and 50 cm) were compared for stand establishment, leaf area and yield during two seasons, under rainfed (upland) conditions. Propagule size and pre-planting storage depth increased both the number of plants reaching the third leaf stage and leaf area per plant one month after planting. The large propagules improved stand establishment and yield significantly (P<0.01) better than the smaller propagules. For all propagule sizes, the optimum storage depth to enhance taro propagule performance for crop production was ∼ 40 cm. When the large propagules were compared with the smaller propagules at the optimum pre-planting storage depth, there was 10% to 30%, no difference and 5% to 35% improvement in leaf area, stand establishment and yield, respectively. This study confirmed the potential role of local knowledge in traditional agriculture, and the findings can be used to extend the planting season for dryland taro production in South Africa.