Thesis (MTech (Food Technology))--Cape Peninsula University of Technology, 2016. / The aim of this study was to evaluate Bambara groundnut (BGN) milk subjected to spray drying with a view to establish functional, nutritional and physical properties as an ingredient in BGN yoghurt production. BGN milk powder (BGNMP) was successfully produced employing the spray drying technology. Maltodextrin was used as the drying carrier to elevate total solids of BGNM prior to spray drying. There were three levels of maltodextrin (5, 10 and 15%) employed and 10% was ideal. The optimum spray drying parameters were estimated to be the following; inlet temperature (150oC), outlet temperature (74oC), air pressure (3 bars), flow rate (10% or 16mL/min), and air flow (42.9 m3/h). The functional properties evaluated revealed high water solubility capabilities, making BGNMP readily soluble in water, which is one of the most crucial aspects of milk powders. The water solubility index of BGNMP at all maltodextrin levels ranged from 85.15 to 90.25%. There was a significant (p < 0.05) difference amongst BGNMP (5, 10, and 15%) in colour parameters (lightness, yellowness, redness, chroma and hue angle). BGNMP indicated to have a red and yellow colour, but yellow was more dominant. The particle size and particle size distribution of BGNMP ranged from 86.13 to 162.35 μm and 84.04 to 157.0 μm, respectively and did not differ significantly (p > 0.05).

Text in English with abstracts in isiVenda and Sepedi / Bambara groundnut and cowpea are essential legumes that are well adapted to unfavourable environmental conditions and have high dietary values for humans. However, they are under-researched and under-utilised. Thus, there are limited records on yields and metabolic profiling of these leguminous crops co-inoculated with B. japonicum and Bacillus subtilis. Generally, very few studies have reported on the effects of co-inoculation of other plant growth-promoting rhizobacteria and rhizobia strains on leguminous plants. This study therefore assessed the effects of B. subtilis (strain BD233) on germination of Bambara groundnut under different temperature regimes, and evaluated the effects of co-inoculation of B. japonicum and B. subtilis on yields of cowpea under glasshouse conditions. The study also assessed the metabolite profile of the crops using 1H nuclear magnetic resonance (NMR) spectroscopy. The data showed that inoculation of Bacillus subtilis on Bambara groundnut landraces under different temperatures enhanced germination (germination percentage, germination rate indices and plumule length). Furthermore, co-inoculation with B. japonicum and Bacillus subtilis (strain BD233) improved plant yield of cowpea plants. Partial least squares-discriminant analysis (PLS-DA) revealed distinct separations between treatments (co-inoculation of B. japonicum and Bacillus subtilis, inoculation of B. japonicum, uninoculated plus NO3 and zero inoculation) on Bambara groundnut and cowpea plants. The VIP score revealed that co-inoculation with B. japonicum and Bacillus subtilis (strain BD233) resulted in low concentrations of metabolites in Bambara groundnut plants and in contrast, high concentrations of metabolites in cowpea plants. Co-inoculation with B. japonicum and Bacillus subtilis (strain BD233) has a potential of improving yield of both Bambara groundnut and cowpea in sustainable agriculture. The metabolic profile of Bambara groundnut and cowpea subjected to co-inoculation has shown that both crops metabolic composition and profile are highly dependent on co-inoculation. / Phonda na ṋawa ndi mangaṋawa a ndeme ane a kona u tea zwavhuḓi kha nyimele dza vhupo vhune ha si vhe havhuḓi na ndeme ya nṱha ya pfushi kha vhathu. Naho zwo ralo, a hu athu u itwa ṱhoḓisiso dzo linganaho nga hadzo na u sa shumiswa Nga zwenezwo hu na rekhodo dzo pimiwaho nga ha khaṋo na u ela tshileme tsha molekulu ṱhukhu dza methaboḽiki dza zwiliṅwa izwi zwa mangaṋawa u khetha na B. japonicum na Bacillus subtilis. Nga u angaredza, ndi ngudo dzi si nngana dzo no vhigwaho nga ha masiandaitwa a khetha nyaluwo ya zwimela zwine zwa ṱuṱuwedza bakitheria dzine dza baḓekanywa na midzi na bakitheria dzine dza shandukisa naiṱirodzheni u vha amonia kha zwimela zwa mangaṋawa. Ngudo heyi nga zwenezwo yo asesa masiandaitwa a B. subtilis (tshiliṅwa tsha BD233) kha mumelo wa phonda nga fhasi ha ndaulo ya thempheretsha dzo fhambanaho, na u ela masiandaitwa a u khetha B. japonicum na B. subtilis kha khaṋo dza phonda na ṋawa nga fhasi ha nyimele ya fhethu hune ha ṱavhiwa zwimela nga fhasi ha tsireledzo kana ndangulo. Ngudo dzo dovha dza ela tshileme tsha molekulu ṱhukhu dza methaboḽiki dza zwiliṅwa hu tshi shumiswa 1H maanḓa a u tzwonzwiwa ha nyukiḽia nga eḽekiṱhironiki maginethe (NMR) nga u ṱanganelana ha radiesheni ya eḽekiṱhironiki maginethe. Data yo sumbedza u ḓivhadzwa ha Bacillus subtilis kha tshiliṅwa tshapo tsha phonda fhasi ha thempheretsha dzo fhambanaho u khwinisa mumelo (phesenthedzhi ya mumelo, zwisumbi zwa phimo ya muelo na vhulapfu ha pulumule). U isa phanḓa, u ḓivhadzwa hafhu ha B. japonicum na Bacillus subtilis (tshiliṅwa tsha BD233) khaṋo yo khwiniswaho ya tshiliṅwa kha zwimela zwa ṋawa. Musaukanyo wa u khethekanya zwitatisiṱika (Partial least squares-discriminant analysis) (PLS-DA) wo sumbedza khethekanyo dzo fhambanaho vhukati ha kushumisele (u ḓivhadzwa hafhu ha B.japonicum na Bacillus subtilis, u ḓivhadzwa ha B. japonicum, i songo ḓivhadzwaho hafhu na NO3 na ziro i songo ḓivhadzwa hafhu) kha phonda na zwiliṅwa zwa ṋawa. Tshikoro tsha VIP tsho wanulusa uri u ḓivhadzwa hafhu ha B. japonicum na Bacillus subtilis (kha tshiliṅwa tsha BD233) zwo bveledza mutzwonzwo wa fhasi wa methobolaithisi kha zwiliṅwa zwa phonda na phambano, ya mutzwonzwo wa nṱha wa methobolaithisi kha zwiliṅwa zwa ṋawa. U khetha ha B. japonicum na Bacillus subtilis (kha tshiliṅwa tsha BD233) zwo vha na ndeme ya u khwinisa khaṋo ya vhuvhili hazwo phonda na ṋawa kha vhulimi vhu sa nyeṱhi. U ela tshileme tsha molekulu ṱhukhu dza methaboḽiki dza phonda na ṋawa tenda u ḓivhadzwa hafhu ho sumbedza uri vhuvhili ha kubveledzele kwa methaboḽiki ya zwiliṅwa na muelo zwo ḓitika nga maanḓa nga u khetha. / Ditloo tša Bambara ke dipeu tše bohlokwa tšeo di kgonago go phela gabotse go maemo a tikologo yeo e sego ya loka e bile di na le boleng bja godimo bja dijo tšeo di lekanego go batho. Le ge go le bjalo, gona le dinyakišišo tša fase ka tšona le gore ga di šomišwe kudu. Ka gona, go na le direkhoto tše dinnyane ka ga pego ya mehola le tšhomišo ya yona ka ga dibjalo tše tša go dira dipeu tšeo di kopantšhwago le B. japonicum le Bacillus subtilis. Ka kakaretšo, dinyakišišo tše dinnyane kudu di begile ka ga dikhuetšo tša kopantšho ya mehlare e mengwe ya go huetša go gola ga pakteria ya medu (rhizobacteria) le dingangego tša pakteria ya ka gare ga medu (rhizobia) go dibjalo tša dipeu. Nyakišišo ye ka gona e lekotše dikhuetšo tša B. subtilis (strain BD233) go melo ya ditloo tša Bambara ka fase ga maemo a dithempereitšha tša go fapana, le go lekola dikhuetšo tša kopantšho ya B. japonicum le B. subtilis go mehola ya ditloo tša Bambara le dinawa ka fase ga maemo a ntlo ya digalase. Nyakišišo gape e lekotše pego ya tšhomišo ya dibjalo go šomišwa sedirišwa sa go laetša maatlakgogedi sa 1H (NMR). Tshedimošo e bontšhitše gore tsenyo ya Bacillus subtilis go ditloo tša Bambara tša tlwaelo ka fase ga dithempereitšha tša go fapana go kaonafaditše go mela (phesente ya go mela, lebelo la dikelo tša melo le botelele bja kutu ya sebjalo). Gape, kopantšho le B. japonicum le Bacillus subtilis (strain BD233) go kaonafaditše mehola ya dibjalo tša mehlare ya dinawa. Tshekatsheko ya go hwetša tswalano ya dithišu tše pedi (PLS-DS) e utollotše ditlogelano tša go fapana magareng ga mekgwa (kopantšho ya B. japonicum le Bacillus subtilis, tsenyo ya B. japonicum, yeo e sego ya tsenywa le NO3 le tsenyo ya lefeela) go ditloo tša Bambara le dibjalo tša dinawa. Dipoelo tša VIP di utollotše gore kopantšho ya B. japonicum le Bacillus subtilis (strain BD233) e tlišitše dipoelo tša fase tša ditšweletšwa tša dimolekule tša dibjalo tša ditloo tša Bambara e bile gape ge re dira phapanyo, bontšhi bjo bo lego godimo bja ditšweletšwa tša dimolekule ka go dibjalo tša dinawa. Kopantšho ya B. japonicum le Bacillus subtilis (strain BD233) e na le kgonagalo ya go kaonafatša mehola ya bobedi ditloo tša Bambara le dinawa ka go temo ya sa ruri. Seemo sa ditšweletšwa tša ditloo tša Bambara le dinawa tšeo di dirilwe kopantšho se bontšhitše gore bobedi tlhamotšweletšo le seemo sa dibjalo tše di ithekgile kudu mo go kopantšho. / Agriculture and  Animal Health / M. Sc. (Agriculture)

This study evaluates how future climatic projections will affect the suitability of bambara groundnut (Vigna subterranean(L) Verdc.), a type of underutilised crop in Sikasso and Ségou, southern Mali. This study was performed using a simulation approach, which considered the potential changes in suitability due to projected changes in two climate variables; temperature and precipitation. Monthly outputs of the two climate variables from 10 CORDEX bias-corrected regional projections under the Representative Concentration Pathway (RCP) 8.5 were applied. The suitability index range of bambara groundnut was projected, using the Ecocrop suitability model, considering three time periods: historical (1975-2005), near-term (2011-2040), and end of century (2070-2099). The results of this study showed that the model captured a long planting window for the crop in the regions across the time periods. With the projected increase in future climatic conditions, the suitability index range of bambara groundnut is projected to increase across the months suitable for planting the crop. Furthermore, Sikasso is projected to maintain a high suitability index in the near-term, and by the end of century, Ségou is expected to experience a potential increase in suitability index range and suitable areas, especially by the end of century. The results indicate that the CORDEX projections and suitability modelling technique applied in the study captured well the suitability of bambara groundnut in the regions which can help the farmers in making planting decisions. These results suggest an opportunity for optimal utilisation of the crop in the regions, as with a long planting window and expansion in suitable areas, farmers in the regions can plant multiple times and have more suitable areas to cultivate. This study contributes to improving the decision-making surrounding the promotion of underutilised crops as part of the strategy for climate-resilient agriculture and food security in Sikasso and Ségou.

MSCAGR (Plant Production) / Department of Plant Production / See the attached abstract below

MSCAGR (Plant Production) / Department of Plant Production / Bambara groundnut (Vigna subterranea) is one of the most important legumes cultivated primarily for food by smallholder farmers in Africa. It is an affordable source of protein and contributes to income generation as well as soil fertility. Despite its importance, it is cultivated largely for subsistence purposes in South Africa. Growers use landraces. The agronomic performance of the traditional varieties depends on environmental factors prevailing in a particular area. In Limpopo and Mpumalanga Provinces, there is no adequate information regarding the performance of bambara groundnut germplasm. The objectives of the study were to (i) determine the agronomic performance of Bambara groundnut across three contrasting locations in Limpopo and Mpumalanga provinces over two cropping seasons (ii) determine the genotypic variation in the seed protein level among 42 bambara groundnut genotypes. Forty-two bambara groundnut genotypes were evaluated under three different environmental conditions (Syferkuil, Thohoyandou and Nelspruit) over two (2013/2014, 2014/2015) seasons in a 7 × 6 rectangular lattice design replicated three times. Eight agronomic traits including dry shoot weight (DSW), number of pods per plant (NPP), pod length (PL), number of seed per pod (NSP), pod weight per plant (PWT), seed weight per plant (SWT), 100 seed weight (100-SWT) and seed yield (SYLD) were measured. The results showed that there were significant genotype x location interactions which demonstrated that the prevailing agro-ecological conditions at the test locations were distinct from each other. Five genotypes (‘BGN-19‘, ‘BGN-11‘, ‘BGN-12‘, ‘BGN-4‘and ‘BGN-34‘) attained >25.0% seed yield advantage over the local check ‘BGN-39‘. The results also showed that light brown coloured genotypes attained relatively higher seed yield compared to the other seed colours types. The cultivar superiority index (CSI) showed that three genotypes (‘BGN-12‘, ‘BGN-19’ and ‘BGN-34’) were the most stable across the test locations and attained >900.0 kg/ha on average. There were significantly high positive correlations between PWT and each of the three other attributes (SWT, 100 SWT and SYLD). In terms of seed protein, the results showed a poor relationship between seed yield and protein levels. ‘BGN-12’ which produced the highest seed yield, attained the lowest percent seed protein while genotype. On average, the genotypes contained 21.72% protein. The highest and lowest seed protein quantities were attained by the genotypes ‘BGN-42’ (25.17%) and ‘BGN-12’ (19.89%) respectively. / NRF

Thesis (MTech (Agriculture))--Cape Peninsula University Of Technology, 2016. / Bambara groundnut (Vigna subterranea), a dicotyledonous plant is a legume which has a potential to contribute to food security and nutrition. Protoplasts are naked plant cells lacking cell walls. Viable protoplasts are potentially totipotent. Therefore, when given the correct stimuli, each protoplast is capable, theoretically, of regenerating a new wall and undergoing repeated mitotic division to produce daughter cells from which fertile plants may be regenerated through the tissue culture process. Protoplast systems are valuable and versatile cell based systems that are useful in observing cellular processes and activities. In this study, the isolation of protoplast from the leaves of Bambara groundnut plant was extensively optimised. The factors affecting protoplast isolation considered in this study were ages of plant material, mannitol concentration, combinations and concentrations of enzymes and duration of incubation. Effects of ages of Bambara groundnut plant (4, 6, 8, 10 weeks), molarities of mannitol (0.4 M, 0.5 M. 0.6 M and 0.7 M), concentration and combination of enzymes (1%, 2% and 4% cellulase, 0.5% and 1% macerozyme and, 0.5% and 1% pectinase) at different incubation duration (4, 18, 24, 42 hours) were investigated. Overall, it can be deduced from this study that the optimal protoplast yield (4.6 ± 0.14×105ml-1/gFW) and viability (86.5 ± 2.12%) were achieved by digesting the leaves of four week old Bambara groundnut plant with 2% cellulase and 0.5 % macerozyme with 0.5M mannitol for 18 hours. Freshly isolated protoplasts were then cultured at different densities of 1 × 104 - 2 ×106 protoplasts/ml using MS in three different culture (Liquid, agar and agarose bead) methods. First cell division was observed only in liquid medium. With several attempts, no division was achieved in the agar and agarose bead methods, division also did not progress in the liquid medium and hence, plant regeneration from Bambara groundnut protoplasts could not be achieved in this study. Consequently, a further study is underway to compare the proteomic profiles of freshly isolated protoplasts and cultured protoplasts in order to gain insights into the expression of proteins that could perhaps be contributing to the difficulty in regenerating Bambara groundnut plant through protoplast technology. The present study is novel because it is the first study to optimise the various factors that could affect protoplast isolation from the leaves of Bambara groundnut and thus developed an efficient protocol for protoplasts isolation from leaves of Bambara groundnut for cell manipulation studies.

M. Tech. (Department of Biotechnology, Faculty of Applied and Computer Sciences), Vaal University of Technology / Bambara groundnut (Vigna subterranea L. Verdc) is an underutilized crop in the African continent. It is a drought tolerant crop and fixes atmospheric nitrogen. Bambara groundnut is primarily grown for the protein content of its seeds and is mainly produced by small scale farmers at the subsistence level. However, despite its importance as a subsistence crop in many African countries, only local landraces of bambara groundnut are still cultivated. Mass selection of a few local varieties for the main agronomic characteristics has been carried out. All the bambara groundnut germplasm in South Africa has not been morphologically characterized. Although the protein of bambara groundnut is of good quality and is rich in lysine, there is no information on the characterisation of these proteins. The presence of antinutritional factors in the crop has also received little attention. This study focused on three major objectives including: (I) to assess the extent of morphological variations among thirty selected landraces of bambara groundnut, (II) to characterize the major seed proteins in these accessions using one dimensional gel electrophoresis, and (III) to determine the presence of any anti-nutritional factors in the seeds of the selected bambara groundnut landraces. 30 accessions of bambara groundnut were evaluated for their variability in agronomic and morphological traits. The field experiment was conducted at ARC-VOPI in Roodeplaat research farm during the 2014/2015 summer cropping season. The field trial was arranged as a complete randomized block design with 3 replications. 18 quantitative traits were recorded to estimate the level of genetic variability among accessions. 4 different methods were employed to extract seed proteins from 30 bambara groundnut accessions in order to ascertain the best method for protein extraction. These methods included: 10%-80% isopropanol, 10% trichloroacetic acid (TCA) in acetone solution, sonication and 2x Lammeli buffer extraction methods. The quick start Qubit® fluorometer protein kit was used to determine the protein concentration in each sample. The samples were then subjected to one dimensional gel electrophoresis. For antinutritional analysis, 5 factors (condensed tannins, free and phytic acid phosphate, polyphenol and trypsin contents) were used to determine the amount of antinutrient in 30 bambara seeds that were ground to a fine powdery flour. 3 replicates of all the samples were ground for each assay evaluated. The flour was then immediately extracted and used for the different assays. The analysis of variance revealed significant differences only in 10 of the 18 phenotypic traits that were evaluated. The UPGMA cluster analysis based on the quantitative traits produced vii four distinct groups of genotypes and a singleton. Genotypes SB11-1A, SB19-1A, SB12-3B and Bambara-12 were found to possess good vegetative characters and are recommended for use as suitable parents when breeding cultivars for fodder production. Desirable yield and yield-related traits were identified in B7-1, SB4-4C, SB19-1A, Bambara-12 and SB16-5A and are recommended as suitable parental lines for bambara groundnut grain production improvement. The quantitative characters therefore provided a useful measure of genetic variability among bambara genotypes and will enable the identification of potential parental materials for future breeding programmes in South Africa. Out of the 4 different seed protein extraction methods exploited for this study, the 2x Laemmli buffer extraction method produced the best result with clear protein bands. A unique feature from all extraction methods was the presence of a common protein band at ̴ 75 kDa. All extraction methods except 10 % TCA-Acetone resolved common banding patterns in all the bambara groundnut samples. This data suggests that there is very little or no intraspecific genetic diversity among the seed proteins of bambara groundnut accessions studied. There was wide variation in the content of the five antinutritional compounds among the thirty bambara groundnut accessions. The mean values for condensed tannin content ranged between 0.20 - 6.20 mg/g. Free phosphate recorded an overall mean of 1.71 mg/g while a range of 1.35 - 4.93 mg/g was observed by phytic acid phosphate (PAP). The polyphenol content had an overall mean of 0.39 mg/g and trypsin inhibitor (TIA) was quite variable among the bambara groundnut accessions ranging from 5.30 - 73.40 TIA/mg. Generally, higher levels of antinutrients were observed in this study compared to the other studies. The results obtained in this study led to a conclusion that although variations exits among the accessions studied, further research is required to verify the extent of morphological variations, the efficiency of protein extractions methods evaluated and the effects of these antinutrients in human and animal feeds.

Thesis presented in partial fulfilment of the requirements for the degree of Master of Technology (Food Technology) Department of Food Technology Faculty of Applied Sciences Cape Peninsula University of Technology, 2012 / The aim of this study was to evaluate bambara groundnut milk (BGNM) subjected to fermentation with lactic acid bacteria (LAB) as a probiotic beverage with a view to developing value-added product. Central Composite Rotatable Design (CCRD) was used to optimise the hydration time and temperature of BGN flour for optimum BGN milk (BGNM) production. The optimum time and temperature was 2 h at 25oC. The effect of variety was assessed on the quality and consumer acceptability of BGNM prepared from five varieties of BGN (black, red, brown, brown-eye, and black-eye) which were representatives of the BGN available in South Africa. BGNM from the five varieties differed significantly (p<0.05) in, lightness, chroma, redness, yellowness, hue and antioxidative activity, while the pH were not significantly different. The four BGNM samples were significantly different (p < 0.05) in appearance, colour, mouthfeel and overall acceptability but not in aroma and taste. A three factor design (4 x 3 x 3) consisting of probiotics (Lactobacillus acidophilus, L. bulgaricus, L. casei and L. plantarum), temperature and fermentation time, were used to estimate the optimal conditions for the production of BGN probiotic beverage (BGNPB). The optimal condition for the production of BGNPB was estimated to be 35oC for 24 h with a desirability of 0.854 for L. bulgaricus. The next promising probiotic was L. plantarum that could be fermented at 35oC for 24 h with 0.843 desirability. BGNM from the red variety were fermented with L. bulgaricus and L. plantarum and L bulgaricus (in combination), making plain and sweetened BGNPB which were evaluated for their quality and consumer acceptability. The four BGNPB samples were significantly different (p < 0.05) in aroma, taste, mouthfeel and overall acceptability but not in appearance and colour. The plain BGNPB were assessed for their proximate composition, antioxidant activity, in vitro probiotic tolerance to simulated gastric juices and bile and a 28 days shelf life study at 5, 15 and 25oC. The protein, total dietary fibre (TDF), ash and antioxidative activity of the BGNPB were significantly different while the fat and carbohydrates were not significantly different. Time and concentration of the gastric juice and bile had significant effects on the percentage bacterial survival of probiotics in the BGNPB. However, the probiotics did survive, in low numbers, in the simulated gastric juice and bile after 180 and 240 minutes of incubation. Titratable acidity, pH, microbial load and colour of the BGNPB were significantly affected by the storage time and temperature during the shelf life study. At the 5oC storage temperature the BGNPB had a right censored shelf life on day 28. At 15oC the shelf life was 18 and 10 days for L bulgaricus and L. plantarum and L. bulgaricus respectively. The outcome of this research showed that a novel BGNPB product can be made from fermenting BGNM with LAB.

Issues surrounding water scarcity will become topical in future as global fresh water resources become more limited thus threaten crop production. Predicted climate change and increasing population growth will place more pressure on agriculture to produce more food using less water. As such, efforts have now shifted to identifying previously neglected underutilised species (NUS) as possible crops that could be used to bridge the food gap in future. Taro (Colocasia esculenta L. Schott) and bambara groundnut (Vigna subterranea L. Verdc) currently occupy low levels of utilisation in South Africa. Both crops are cultivated using landraces with no improved varieties available. Information describing their agronomy and water–use is limited and remains a bottleneck to their promotion. The aim of this study was to determine the drought tolerance and water–use of selected landraces of taro and bambara groundnut from KwaZulu-Natal, South Africa. In order to meet the specific objectives for taro and bambara groundnut management, an approach involving conventional and modelling techniques was used. Three taro landraces [Dumbe Lomfula (DL), KwaNgwanase (KW) and Umbumbulu (UM)] were collected from the North Coast and midlands of KwaZulu-Natal, South Africa, in 2010. The UM landrace was classified as Eddoe type taro (C. esculenta var. antiquorum) characterised by a central corm and edible side cormels. The DL and KW landraces were classified as Dasheen (C. esculenta var. esculenta), characterised by a large edible main corm and smaller side cormels. A bambara groundnut landrace was collected from Jozini, KwaZulu- Natal, and characterised into three selections (‘Red’, ‘Light-brown’ and ‘Brown’) based on seed coat colour. Seed colour was hypothesised to have an effect on seed quality. Field and rainshelter experiments were conducted for both taro and bambara landraces at Roodeplaat in Pretoria and Ukulinga Research Farm in Pietermaritzburg, over two growing seasons (2010/11 and 2011/12). The objective of the field trials for taro and bambara groundnut was to determine mechanisms associated with drought tolerance in taro and bambara groundnut landraces. Experiments were laid out in a split-plot design where irrigation [fully irrigated (FI) and rainfed (RF)] was the main factor and landraces (3 landraces of either taro or bambara groundnut) were sub-factors. Treatments were arranged in a randomised complete block design (RCBD), replicated three times. Rainfed trials were established with irrigation to allow for maximum crop stand. Thereafter, irrigation was withdrawn. Whilst experimental designs and layouts for taro and bambara groundnut were similar, differences existed with regards to plot sizes and plant spacing. Trials were planted on a total land area of 500 m2 and 144 m2, for taro and bambara groundnut, respectively. Plant spacing was 1 m x 1 m for taro and 0.3 m x 0.3 m for bambara groundnut. Irrigation scheduling in the FI treatment was based on ETo and Kc and was applied using sprinkler irrigation system. Separate rainshelter experiments were conducted for taro and bambara groundnut landraces at Roodeplaat, to evaluate growth, yield and water-use of taro and bambara groundnut landraces under a range of water regimes. The experimental design was similar for both crops, a RCBD with two treatment factors: irrigation level [30, 60 and 100% crop water requirement (ETa)] and landrace (3 landraces), replicated three times. Irrigation water was applied using drip irrigation system based on ETo and Kc. Data collection in field and rainshelter trials included time to emergence, plant height, leaf number, leaf area index (LAI), stomatal conductance and chlorophyll content index (CCI). For taro field trials, vegetative growth index (VGI) was also determined. Yield and yield components (harvest index, biomass, corm number and mass) as well as water–use efficiency (WUE) were determined at harvest. Intercropping of taro and bambara groundnut was evaluated under dryland conditions using farmers’ fields at Umbumbulu, KwaZulu–Natal, South Africa. The experimental design was a RCBD replicated three times. Intercrop combinations included taro and bambara groundnut sole crops, a 1:1 (one row taro to one row bambara groundnut) and 1:2 intercrop combinations. The taro UM landrace and ‘Red’ bambara groundnut landrace selection were used in the intercropping study. Lastly, data collected from field and rainshelter experiments were used to develop crop parameters to calibrate and validate the FAO’s AquaCrop model for taro and bambara groundnut landraces. The UM landrace was used for taro while the ‘Red’ landrace selection was used for bambara groundnut. AquaCrop was calibrated using observed data from optimum (FI) experiments conducted during 2010/11. Model validation was done using observations from field and rainshelter experiments conducted during 2011/12 as well as independent data. Results showed that all taro landraces were slow to emerge (≈ 49 days after planting). Stomatal conductance declined under conditions of limited water availability (RF, 60% and 30% ETa). The UM landrace showed better stomatal regulation compared with KW and DL landraces under conditions of limited water availability. Plant growth (plant height, leaf number, LAI and CCI) of taro landraces was lower under conditions of limited water availability (RF, 60% and 30% ETa) relative to optimum conditions (FI and 100% ETa). The UM landrace showed moderate reductions in growth compared with the DL and KW landraces, suggesting greater adaptability to water limited conditions. The VGI showed a large reduction in growth under RF conditions and confirmed the UM landrace’s adaptability to limited water availability. Limited water availability (RF, 60% and 30% ETa) resulted in lower biomass, HI, and final yield in taro landraces relative to optimum conditions (FI and 100% ETa). For all trials, the DL landrace failed to produce any yield. WUE of taro landraces was consistent for the three irrigation levels (30, 60 and 100% ETa); however, on average, the UM landrace was shown to have a higher WUE than the KW landrace. Bambara groundnut landraces were slow to emerge (up to 35 days after planting). ‘Red’ and ‘Brown’ landrace selections emerged better than the ‘Light-brown’ landrace selection, confirming the effect of seed colour on early establishment performance. Plant growth (stomatal conductance, CCI, plant height, leaf number, LAI and biomass accumulation) was lower under conditions of limited water availability (RF, 60% and 30% ETa) relative to optimum conditions (FI and 100% ETa). The ‘Red’ landrace selection showed better adaptation to stress. Limited water availability resulted in early flowering and reduced flowering duration as well as early senescence and maturity of bambara groundnut landrace selections. The ‘Red’ landrace selection showed delayed leaf senescence under conditions of limited water availability. Yield reductions of up to 50% were observed under water limited conditions (RF, 60% and 30% ETa) relative to optimum conditions (FI and 100% ETa). Water use efficiency increased at 60% and 30% ETa, respectively, relative to 100% ETa, implying adaptability to limited water availability. The ‘Red’ landrace selection showed better yield stability and WUE compared with the ‘Brown’ and ‘Light-brown’ landrace selections suggesting that seed colour may be used as a selection criterion for drought tolerance in bambara groundnut landraces. The intercropping study showed that intercropping, as an alternative cropping system, had more potential than monocropping. Evaluation of growth parameters showed that taro plant height was generally unaffected by intercropping but lower leaf number was observed as compared with the sole crop. Bambara groundnut plants were taller and had more leaves under intercropping relative to the sole crop. Although not statistically significant, yield was generally lower in the intercrops compared with the sole crops. Evaluation of intercrop productivity using the land equivalent ratio (LER) showed that intercropping taro and bambara groundnut at a ratio of 1:1 was more productive (LER = 1.53) than intercropping at a ratio of 1:2 (LER = 1.23). The FAO’s AquaCrop model was then calibrated for the taro UM landrace and ‘Red’ bambara groundnut landrace selection. This was based on observations from previous experiments that suggested them to be drought tolerant and stable. Calibration results for taro and bambara groundnut landraces showed an excellent fit between predicted and observed parameters for canopy cover (CC), biomass and yield. Model validation for bambara groundnut showed good model performance under field (FI and RF) conditions. Model performance was satisfactory for rainshelters. Validation results for taro showed good model performance under all conditions (field and rainshelters), although the model over-estimated CC for the declining stage of canopy growth under RF conditions. Model verification using independent data for taro showed equally good model performance. In conclusion, the taro UM landrace and ‘Red’ bambara groundnut landrace selection were shown to be drought tolerant and adapted to low levels of water–use. The mechanisms responsible for drought tolerance in the taro UM landrace and ‘Red’ bambara groundnut landrace selection were described as drought avoidance and escape. The taro UM landrace and ‘Red’ bambara groundnut landraces avoided stress through stomatal regulation, energy dissipation (loss of chlorophyll) as well as reducing canopy size (plant height, leaf number and LAI), which translates to minimised transpirational water losses. This indicated landrace adaptability to low levels of water–use. The ‘Red’ bambara groundnut landrace selection showed phenological plasticity and escaped drought by flowering early, delaying leaf senescence, and maturing early under conditions of limited water availability. Performance of the ‘Red’ landrace selection lends credence to the use of seed coat colour as a possible selection criterion for drought tolerance in bambara groundnut, and possibly for other landraces with variegated seed. The taro UM landrace escaped drought by maturing early under conditions of limited water availability. The FAO’s AquaCrop model was successfully calibrated and validated for taro UM and ‘Red’ bambara groundnut landraces. The calibration and validation of AquaCrop for taro is the first such attempt and represents progress in the modelling of neglected underutilised crops. The calibration and validation of AquaCrop for taro requires further fine-tuning while that for bambara groundnut still needs to be tested for more diverse landraces. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2011.

Issues surrounding water scarcity will become topical in future as global fresh water resources become more limited thus threaten crop production. Predicted climate change and increasing population growth will place more pressure on agriculture to produce more food using less water. As such, efforts have now shifted to identifying previously neglected underutilised species (NUS) as possible crops that could be used to bridge the food gap in future. Taro (Colocasia esculenta L. Schott) and bambara groundnut (Vigna subterranea L. Verdc) currently occupy low levels of utilisation in South Africa. Both crops are cultivated using landraces with no improved varieties available. Information describing their agronomy and water–use is limited and remains a bottleneck to their promotion. The aim of this study was to determine the drought tolerance and water–use of selected landraces of taro and bambara groundnut from KwaZulu-Natal, South Africa. In order to meet the specific objectives for taro and bambara groundnut management, an approach involving conventional and modelling techniques was used. Three taro landraces [Dumbe Lomfula (DL), KwaNgwanase (KW) and Umbumbulu (UM)] were collected from the North Coast and midlands of KwaZulu-Natal, South Africa, in 2010. The UM landrace was classified as Eddoe type taro (C. esculenta var. antiquorum) characterised by a central corm and edible side cormels. The DL and KW landraces were classified as Dasheen (C. esculenta var. esculenta), characterised by a large edible main corm and smaller side cormels. A bambara groundnut landrace was collected from Jozini, KwaZulu- Natal, and characterised into three selections (‘Red’, ‘Light-brown’ and ‘Brown’) based on seed coat colour. Seed colour was hypothesised to have an effect on seed quality. Field and rainshelter experiments were conducted for both taro and bambara landraces at Roodeplaat in Pretoria and Ukulinga Research Farm in Pietermaritzburg, over two growing seasons (2010/11 and 2011/12). The objective of the field trials for taro and bambara groundnut was to determine mechanisms associated with drought tolerance in taro and bambara groundnut landraces. Experiments were laid out in a split-plot design where irrigation [fully irrigated (FI) and rainfed (RF)] was the main factor and landraces (3 landraces of either taro or bambara groundnut) were sub-factors. Treatments were arranged in a randomised complete block design (RCBD), replicated three times. Rainfed trials were established with irrigation to allow for maximum crop stand. Thereafter, irrigation was withdrawn. Whilst experimental designs and layouts for taro and bambara groundnut were similar, differences existed with regards to plot sizes and plant spacing. Trials were planted on a total land area of 500 m2 and 144 m2, for taro and bambara groundnut, respectively. Plant spacing was 1 m x 1 m for taro and 0.3 m x 0.3 m for bambara groundnut. Irrigation scheduling in the FI treatment was based on ETo and Kc and was applied using sprinkler irrigation system. Separate rainshelter experiments were conducted for taro and bambara groundnut landraces at Roodeplaat, to evaluate growth, yield and water-use of taro and bambara groundnut landraces under a range of water regimes. The experimental design was similar for both crops, a RCBD with two treatment factors: irrigation level [30, 60 and 100% crop water requirement (ETa)] and landrace (3 landraces), replicated three times. Irrigation water was applied using drip irrigation system based on ETo and Kc. Data collection in field and rainshelter trials included time to emergence, plant height, leaf number, leaf area index (LAI), stomatal conductance and chlorophyll content index (CCI). For taro field trials, vegetative growth index (VGI) was also determined. Yield and yield components (harvest index, biomass, corm number and mass) as well as water–use efficiency (WUE) were determined at harvest.Intercropping of taro and bambara groundnut was evaluated under dryland conditions using farmers’ fields at Umbumbulu, KwaZulu–Natal, South Africa. The experimental design was a RCBD replicated three times. Intercrop combinations included taro and bambara groundnut sole crops, a 1:1 (one row taro to one row bambara groundnut) and 1:2 intercrop combinations. The taro UM landrace and ‘Red’ bambara groundnut landrace selection were used in the intercropping study. Lastly, data collected from field and rainshelter experiments were used to develop crop parameters to calibrate and validate the FAO’s AquaCrop model for taro and bambara groundnut landraces. The UM landrace was used for taro while the ‘Red’ landrace selection was used for bambara groundnut. AquaCrop was calibrated using observed data from optimum (FI) experiments conducted during 2010/11. Model validation was done using observations from field and rainshelter experiments conducted during 2011/12 as well as independent data. Results showed that all taro landraces were slow to emerge (≈ 49 days after planting). Stomatal conductance declined under conditions of limited water availability (RF, 60% and 30% ETa). The UM landrace showed better stomatal regulation compared with KW and DL landraces under conditions of limited water availability. Plant growth (plant height, leaf number, LAI and CCI) of taro landraces was lower under conditions of limited water availability (RF, 60% and 30% ETa) relative to optimum conditions (FI and 100% ETa). The UM landrace showed moderate reductions in growth compared with the DL and KW landraces, suggesting greater adaptability to water limited conditions. The VGI showed a large reduction in growth under RF conditions and confirmed the UM landrace’s adaptability to limited water availability. Limited water availability (RF, 60% and 30% ETa) resulted in lower biomass, HI, and final yield in taro landraces relative to optimum conditions (FI and 100% ETa). For all trials, the DL landrace failed to produce any yield. WUE of taro landraces was consistent for the three irrigation levels (30, 60 and 100% ETa); however, on average, the UM landrace was shown to have a higher WUE than the KW landrace. Bambara groundnut landraces were slow to emerge (up to 35 days after planting). ‘Red’ and ‘Brown’ landrace selections emerged better than the ‘Light-brown’ landrace selection, confirming the effect of seed colour on early establishment performance. Plant growth (stomatal conductance, CCI, plant height, leaf number, LAI and biomass accumulation) was lower under conditions of limited water availability (RF, 60% and 30% ETa) relative to optimum conditions (FI and 100% ETa). The ‘Red’ landrace selection showed better adaptation to stress. Limited water availability resulted in early flowering and reduced flowering duration as well as early senescence and maturity of bambara groundnut landrace selections. The ‘Red’ landrace selection showed delayed leaf senescence under conditions of limited water availability. Yield reductions of up to 50% were observed under water limited conditions (RF, 60% and 30% ETa) relative to optimum conditions (FI and 100% ETa). Water use efficiency increased at 60% and 30% ETa, respectively, relative to 100% ETa, implying adaptabilityto limited water availability. The ‘Red’ landrace selection showed better yield stability and WUE compared with the ‘Brown’ and ‘Light-brown’ landrace selections suggesting that seed colour may be used as a selection criterion for drought tolerance in bambara groundnut landraces. The intercropping study showed that intercropping, as an alternative cropping system, had more potential than monocropping. Evaluation of growth parameters showed that taro plant height was generally unaffected by intercropping but lower leaf number was observed as compared with the sole crop. Bambara groundnut plants were taller and had more leaves under intercropping relative to the sole crop. Although not statistically significant, yield was generally lower in the intercrops compared with the sole crops. Evaluation of intercrop productivity using the land equivalent ratio (LER) showed that intercropping taro and bambara groundnut at a ratio of 1:1 was more productive (LER = 1.53) than intercropping at a ratio of 1:2 (LER = 1.23). The FAO’s AquaCrop model was then calibrated for the taro UM landrace and ‘Red’ bambara groundnut landrace selection. This was based on observations from previous experiments that suggested them to be drought tolerant and stable. Calibration results for taro and bambara groundnut landraces showed an excellent fit between predicted and observed parameters for canopy cover (CC), biomass and yield. Model validation for bambara groundnut showed good model performance under field (FI and RF) conditions. Model performance was satisfactory for rainshelters. Validation results for taro showed good model performance under all conditions (field and rainshelters), although the model over-estimated CC for the declining stage of canopy growth under RF conditions. Model verification using independent data for taro showed equally good model performance. In conclusion, the taro UM landrace and ‘Red’ bambara groundnut landrace selection were shown to be drought tolerant and adapted to low levels of water–use. The mechanisms responsible for drought tolerance in the taro UM landrace and ‘Red’ bambara groundnut landrace selection were described as drought avoidance and escape. The taro UM landrace and ‘Red’ bambara groundnut landraces avoided stress through stomatal regulation, energy dissipation (loss of chlorophyll) as well as reducing canopy size (plant height, leaf number and LAI), which translates to minimised transpirational water losses. This indicated landrace viii adaptability to low levels of water–use. The ‘Red’ bambara groundnut landrace selection showed phenological plasticity and escaped drought by flowering early, delaying leaf senescence, and maturing early under conditions of limited water availability. Performance of the ‘Red’ landrace selection lends credence to the use of seed coat colour as a possible selection criterion for drought tolerance in bambara groundnut, and possibly for other landraces with variegated seed. The taro UM landrace escaped drought by maturing early under conditions of limited water availability. The FAO’s AquaCrop model was successfully calibrated and validated for taro UM and ‘Red’ bambara groundnut landraces. The calibration and validation of AquaCrop for taro is the first such attempt and represents progress in the modelling of neglected underutilised crops. The calibration and validation of AquaCrop for taro requires further fine-tuning while that for bambara groundnut still needs to be tested for more diverse landraces. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2011.