Bambara groundnut (Vigna subterranea (L.) Verdc.) is a leguminous crop indigenous to Africa, which is grown by small-scale farmers. It is a protein rich legume crop, which is mostly grown to supply rural and urban poor communities with a nutritious source of food. In this study six cultivars of bambara groundnut seeds differing in seed coat colour were used to determine the seed-borne mycoflora present on the seed and whether this was related to surface topography and/or, the amount and localisation of polyphenolic compounds in the seed. Bambara groundnut seeds were surface sterilised with 1.5% sodium hypochlorite for 5min, plated on PDA petri dishes and incubated at ±25°C. After 7d of incubation, percentage of fungal infestation was determined. It was found that dark coloured seeds (Sb4- 4A and Sb 8-1) of bambara groundinut were less infected, with the exception of one dark cultivar (Swazi Vs A), than the light coloured seeds (As7 and Sbas 1-8). Aspergillus, Fusarium and Chaetomium spp. were found to be the dominant fungal species. Scanning electron microscopy was used to determine if seed infection of the various cultivars could be linked to seed surface topography. Seeds were cut in half, placed directly on stubs and coated with gold. Examination of surface topography indicated that there were no distinct morphological differences among the different cultivars. The seeds had smooth surfaces and although some showed a little shrinkage, none had structures like pores or pits. Hilum structures differed among cultivars and were either tightly or loosely packed. As seed fungal infection could not be linked directly to surface topography, the amount and localization of polyphenolic compounds was then studied to determine whether these factors may influence fungal infection. In the histochemistry study, 10μm seed coat sections were mounted in glycerine or vanillin-HCI. Other sections were stained with Neu reagent. Illumination was recorded at 420nm and 360nm for blue and UV light respectively. Thin layer chromatography (TLC) was performed to separate phenolic compounds. It was found that dark coloured seeds were stained dark red showing the presence of polyphenolic compounds in the epidermis and parenchymatous layer. Dark coloured seeds emitted a strong blue fluorescence under UV illumination indicating the presence of large quantities of polyphenolic compounds in the epidermis. This was not apparent in the light coloured seeds. Under blue illumination, the green colouration of the epidermis indicated the presence of flavonoids, which also appeared to be more apparent in darker seeds than in light coloured seeds. This difference is brought about by the different amounts of total phenolic compounds in the seeds. The amount of phenolic compounds was higher in the seed coats than in the embryo and cotyledons. A TLC study showed more compounds in the dark coloured seeds than in light coloured seeds. The results of this study indicated that the pdlyphenolic compounds present in the seed coats of bambara groundnut may indeed play a role in the resistance or susceptibility of different coloured seeds to fungal infection. / Dissertation (Magister Institutionis Agrariae)--University of Pretoria, 2005. / Plant Production and Soil Science / unrestricted

There is inadequate basic information available on the reproductive efficiency of peanut (Arachis hypogaea L.) cultivars and a need to determine the sources of yield improvement made in peanut over the past four decades. Therefore, a study of the reproductive efficiency (RE) of 14 virginia market-type peanut cultivars was conducted using field experiments at the Tidewater Research Center, Suffolk, Virginia, in 1983 and 1984. The 14 cultivars vary in maturity from early to late, in release dates from 1944-1981, in breeding method of development from selection within an existing cultivar to hybridization followed by selection, and in growth habit from erect to spreading. The traits studied included flower total (FT), mature pod total (MPT), seed total (ST), pod total (PDT), peg total (PGT), immature pod total (IMPDT), mature pod dry weight (MPDW), plant dry weight (PLDW), vine weight (VW) and seed weight (SW). The five methods used to measure RE were (1) MPDW/PLDW (Harvest Index), (2) MPT/FT, (3) PDT/FT, (4) PGT + PDT/FT and (5) ST/(2*FT). The results indicate that the five most recently released cultivars produced more plowers, 10% more mature pods, 9.7% more mature seeds, and 11% more plant dry weight than the nine previously released cultivars. Using Harvest Index (HI) there was a 4% increase in RE for more recent vs. older cultivars, and about an 8% higher RE for early maturing vs. later maturing cultivars. Also, there was a 3% increase in RE for erect vs. similar advantage for hybrids spreading cultivars and a vs. pure lines. A slight decrease in RE for cultivars released since 1970 vs. those released earlier was observed using Methods 2, 3, 4 and 5. In addition, there was a 4-10% advantage in RE for the two earlier maturing classes over the medium or late classes using the same methods and also a 6% increase in RE for erect vs. spreading cultivars. The growth habit of the 14 cultivars was a very important determining factor for all trait differences. HI appears to be the single best measure of RE in peanuts; however, at least one other method should also be used for obtaining the truest estimate of the RE of a cultivar. It appears that the total peanut cultivar is early maturing and erect with a high RE. This study shows that plant breeders have increased yield in peanuts by (a) increasing apparently the total number of flowers, (b) increasing the HI and (c) increasing reproductive efficiency by increasing the proportion of flowers that form mature pods. Any further increase in yield must combine these three methods of increasing yield as well as overcoming any limiting factors, such as photosynthetic capacity, in order to surpass the present yield plateau. / M.S.

Groundnuts (Arachis hypogaea L.) are an important subsistence and cash crop for smallholder farmers in Southern Africa. They require well drained light textured soils. However, most light textured soils are acidic and inherently infertile, and therefore require supplementary nutrients and amelioration with lime. In addition to application of a basal fertilizer, groundnut production also requires Ca. This increases the inputs required to produce the crop, particularly for smallholder farmers. The study examined two options for smallholder farmers, outside the classical lime application, for ameliorating soil acidity, i.e., evaluating the response of different groundnut genotypes for tolerance to soil acidity and low-cost liming alternatives. Initially ten groundnuts genotypes were screened for tolerance to soil acidity. Following this, three genotypes classified as tolerant and susceptible were used to evaluate the effect of high acid saturation on germination, emergence and seedling establishment. Thereafter, selected cultivars were used to compare calcium silicate, as an alternative to dolomitic lime, for ameliorating soil acidity and supplying calcium to developing pods. All three studies were conducted under controlled conditions: 25 ± 5°C and 20 ± 3°C day/night temperatures, 65% RH. Results measured as plant height, leaf area, yield, concentration and uptake of selected macro-and micro-nutrients showed that different groundnut genotypes differed in their response to soil acidity. Genotypes like Billy, Selmani, Rambo and JL 24 had low Al uptake and high Ca and P uptake and were classified as tolerant to acidity. In addition, these genotypes also had a higher leaf area and high number of nodules compared with Anel, Harts, Sellie, RG 784 and Robbie. With the exception of JL 24 all other tolerant genotypes (Billy, Selmani and Rambo) were large seeded. In the early establishment stage especially, root development was susceptible to soil acidity, but Rambo appeared to perform better than Jasper and Harts. Calcium silicate reduced soil acid saturation and provided enough calcium for pod development, suggesting that it may be used as an additional source of calcium. Soil acidity increased grain protein concentration and reduced its oil content, however, amelioration with either lime source reversed this trend. Thus, growing groundnuts in acid soils has implications for the commercial value of the product in terms of oil or protein supply. Overall, the study suggests that a combination of application of a cheap liming source like calcium silicate and growing tolerant cultivars, like Rambo, Billy and JL 24 might provide a window of opportunity for smallholder farmers to produce groundnuts possibly with only a fraction of the costs associated with ameliorating soil acidity. / Thesis (M.Sc.Agric.)-University of KwaZulu-Natal, Pietermaritzburg, 2011.

Groundnut (Arachis hypogaea L.) is an important food and cash crop in Mozambique and production has been constrained by lack of high-yielding cultivars and disease infection. Objectives of this study were: 1) to identify farmers’ major groundnut production constraints and their preferences for cultivars; 2) to determine genotypic variation among landraces for agro-morphological traits and resistance to groundnut rosette disease; 3) to determine agronomic performance and resistance to groundnut rosette disease among advanced groundnut lines; and 4) to determine the inheritance of resistance to groundnut rosette disease. The study was conducted in northern Mozambique from 2008/2009 to 2010/2011. In attempt to identify farmers’ major groundnut production constraints and their preferences in cultivars, a participatory rural appraisal (PRA) was conducted in Namuno and Erati districts in northern Mozambique. Results from the PRA showed that farmers were aware of the constraints affecting groundnut production and productivity in the study area. The major constraints included groundnut rosette disease, insect pests, lack of seeds and improved cultivars, low soil fertility and lack of infra-structure. Groundnut rosette disease was ranked the most important constraint, and it was widespread in the region. Selection criterion for groundnut cultivars used by women differed from that used by men within village and across villages. However, high yield and oil content were the most important traits preferred by farmers followed by pod and seed size, earliness, disease and insect pest resistance. Fifty-eight groundnut landraces were collected from northern Mozambique (Nampula, Cabo Delgado, Niassa and Zambezia) and evaluated for variation in agro-morphological traits and resistance to groundnut rosette disease. The landraces showed high phenotypic diversity in agro-morphological traits. Clustering by nearest neighbour method indicated that the genotypes could be grouped into six clusters, indicating that agro-morphological diversity exists. The highest yielding genotypes were Pambara-4, Pambara-2, Pambara-6, lle-1, Imponge-1-Tom and Gile-5. There was considerable genetic variability for resistance to groundnut rosette disease among the landraces. Four landraces (PAN-4, Imponge-4, Pambara-3, Metarica Joao) were classified as resistant. No significant correlation was observed between seed yield and groundnut rosette incidence. Thirty-two improved lines were evaluated for performance in two growing seasons across three locations in northern Mozambique (Nampula, Namapa and Mapupulo). The results indicated that the highest yielding genotype was 23A and the highest yielding location was Namapa. There was a significant and negative correlation between seed yield and groundnut rosette disease indicating that the seed yield was negatively influenced by the disease. The results on stability analysis indicated that genotype 35B was the most stable across environments since it had coefficient of regression around unity (bi=1.024), high coefficient of determination (R2=0.999), and small variance deviation (var-dev=162.8), and 13 % above average seed yield. It is, therefore, concluded that genotype 35A could be recommended for cultivation on diverse environments of northern Mozambique. A trial was conducted using the parents and F2 populations derived from a 7 X 7 diallel cross. The test materials were infected with groundnut rosette disease using the spreader-row technique. The results indicated that no genotype was immune to disease. The mean squares due to both general combining ability (GCA) and specific combining ability (SCA) were significant indicating that additive and non-additive gene actions were involved in the expression of resistance to groundnut rosette disease. The general predictability ratio (GCA:SCA) was 0.97, indicating the predominance of additive over non-additive gene action in the inheritance of the disease. The study also found that groundnut rosette disease was controlled by two recessive genes. However, some genetic modifiers may also be present and influence disease expression. In general, the study revealed that breeding opportunities do exist, incorporating farmers preferred traits and major groundnut production constraints into new groundnut cultivars. Improving cultivars for resistance to groundnut rosette disease will be a major breeding focus, while selection for other traits and constraints will not be ignored. Resistance has been identified from local landraces. Advanced lines with high yields across environments were identified that can be recommended for release. The high significant additive effects observed for groundnut rosette disease implied genetic advance could be effective in the F2 and later generations through selection, although modifiers could slow the progress. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2011.

Bambara groundnut is a protein-rich legume, with food security potential in drought-prone regions. It has been grown for many centuries and has remained an important crop to most African subsistence farmers. However, despite its high nutritional status and yield advantages in poor soils, it remains one of the neglected crops by science. There have now been recent efforts to study underutilised crops, with the aim of promoting them as healthy alternatives for people facing resource and environmental challenges and to contribute to food security. In order to do this, there needs to be information that can be used to advise farmers on the agronomic aspects of producing the crop. The overall aim of the study was to evaluate the response of bambara groundnut landraces to drought under controlled environment and field conditions. Seeds were initially collected from subsistence farmers in Jozini, KwaZulu-Natal, and characterised into three seed lots distinguished by seed coat colour: red, white and brown. In the initial study (Chapter 2) seed quality of bambara groundnuts was evaluated. Seed lots were used for standard germination (SG) and cold test (CT). Seeds were germinated under two conditions, 25°C for 8 days (SG) and 4°C for 7 days followed by 8 days at 25°C (CT). Germination percentage, seedling size and mass were determined. Desiccation tolerance was evaluated by suspending 30 seeds of each seed lot over saturated salt solutions of NaCl, LiCl, KNO3 and H2O (control) for 0, 2, 4, 8, 24 and 48 hours. Five seeds were sampled at each interval and stored at -21°C for 7 days. Samples were ground and analysed for proline content. In addition, early establishment performance of bambara groundnut was evaluated under controlled environment conditions in seedling trays using two water regimes (Chapter 2). The experimental design had three factors: seed lot (colour), priming (NaCl, LiCl, KNO3, H2O and control) and water regimes [25% and 75% Field Capacity (F.C.)]. The experiment was replicated three times. Seedling emergence was determined daily for 21 days. Seedling height and leaf number were determined weekly for three weeks, thereafter, seedling leaf area, root and shoot mass (fresh and dry), root and shoot lengths and root to shoot ratio were also determined. Seedlings were later transplanted in 90 pots for a pot trial in order to evaluate growth responses of bambara groundnut to water stress; plant height, leaf number and yield components were determined (Chapter 3). Lastly, the use of planting date selection as a management strategy for managing the occurrence of water stress under field conditions was evaluated in field trials. The experimental design was a split-split-plot design with planting date as main factor (early, optimum and late), irrigation and rainfed as sub-main factor, and seed colour as sub-plots (brown, red and white) arranged in a randomised complete block design (RCBD), with three replications. There were three planting dates: 7 September (early planting), 24 November (optimum planting) and 19 January (late planting). Results from Chapter 2 showed that the brown seed lot had the highest germination across treatments, followed by red and white seeds, respectively. There were significant differences between seed lots (P < 0.05) and salt solutions (P < 0.05) with respect to proline content. Seed proline content increased from 0 to 8 hours and later declined; NaCl was associated with the highest proline accumulation. There were highly significant differences (P < 0.001) between seed colours, priming treatments and F.C., as well as their interaction, with respect to seedling emergence. White seeds had the highest emergence, followed by brown and red, respectively. Priming seeds improved their emergence compared to the control, with highest emergence being observed in seeds treated with LiCl. Priming also improved emergence under water stress; 25% F.C. had the highest emergence compared to 75% F.C. Results from Chapter 3 showed that, seeds primed with NaCl and KNO3 resulted in tallest plants with the highest number of leaves per plant. However, NaCl and KNO3 were also the most affected under water stress. Priming was shown to improve germination and early crop establishment of bambara groundnut landraces under water stress. However, yield per plant did not improve in response to either halo- or hydro-priming. Results from field trials showed that in terms of the measured plant growth parameters (plant height, leaf number and LAI), bambara groundnut landraces were sensitive water stress. Water stress decreased yield components, and hence yield. However, selection of planting dates was shown to be a useful management tool for managing water stress under water limited field conditions. Choice of planting date significantly affected both plant growth and yield. The optimum planting date resulted in the best crop growth for all measured plant growth parameters followed by late and early planting dates, respectively. Seed quality was shown to be associated with seed lot colour. Darker coloured (red and brown) seeds performed better than light (white) seeds with respect to germination. Priming was also shown to improve germination and early crop establishment of bambara groundnut landraces under water stress. However, yield per plant did not improve following priming. Growth of bambara groundnut landraces was shown to be sensitive to water stress. Water stress decreased yield components and hence yield under both controlled and field conditions. Choice of planting date significantly affected both plant growth and yield. The optimum planting date was shown to be the best performing planting date. The findings of this study suggest that bambara groundnut seed performance in terms of germination, stand establishment and productivity is associated with seed lot colour. Seed priming improves seed performance and enhances crop capacity to withstand water stress. If the optimum planting date for groundnuts (late spring to early summer) is missed, better crop performance and yield are obtained from late planting (late summer to early spring) compared with early planting (early spring). Bambara groundnut has a potential for production under water stress conditions in controlled and field environments. / Thesis (M.Sc.Agric.)-University of KwaZulu-Natal, Pietermaritzburg, 2011.

The Eastern Cape Province of South Africa has climatic conditions which differ from region to region. The groundnut (Arachis hypogaea L.) cultivars, as it is the case with other crops, do not always perform equally well in the varying conditions. Abiotic stresses such as drought, extreme temperatures, and high soil acidity restrict plant growth. Lack of studies on adaptability of commercial groundnut cultivars in the Eastern Cape necessitated this study. Abiotic and biotic factors are not the only limiting factors: calcium availability in the soil is also a limiting factor in groundnut production. The aim of the study was to identify best suited cultivars for climatic conditions of Mthatha and Lusikisiki regions of the Eastern Cape. Two similar field experiments were conducted in the two locations with different climatic conditions. The results showed significant differences (P<0.05) in genotypes with respect to seed yield in both locations. Kwarts produced higher seed yield of 1155 kg ha-1 in Mthatha, while the same genotype produced low seed yield of 630 kg ha-1 in Lusikisiki location. In Lusikisiki the highest seed yield was recorded in Anel (936 kg ha-1) which produced low yield of 692 kg ha-1 in Mthatha. The genotypes that performed well in Mthatha in 2010/11 season included Kwarts, Nyanda, ICGV-SM 95714 and Mwenje. These genotypes were further used to investigate their response to calcium supplementation at flowering stage under conditions of Mthatha in the 2011/12 season. The results were significantly different for calcium absorption (P<0.05). Nyanda, Kwarts and Mwenje responded positively to calcium application at flowering stage producing relatively high yield of 153, 150 and 110 kg ha-1, respectively. Oil content was significantly increased by calcium application at flowering in Nyanda with 27.28% compared to 20.7% without Ca.

Groundnut (Arachis hypogaea L.) is one of the most important legume crops in Malawi. However, production among smallholder farmers has declined in recent years. One of the constraints affecting groundnut production is groundnut rosette disease (GRD). Therefore, the main objective of this study was to develop appropriate groundnut cultivars that are resistant to GRD, combined with other traits preferred by farmers, in order to improve income and food security of smallholder farmers in Malawi and beyond. The specific aims were; (i) to assess groundnut cropping systems used by smallholder farmers in Malawi, their varietal preferences, and production challenges (ii) to assess the genetic diversity among groundnut germplasm collected from ICRISAT, the Chitedze gene bank and farmers (iii) to identify sources of resistance to GRD and to its aphid vector (iv) and to understand the type of gene action governing GRD resistance, and to identify groundnut genotypes suitable for use as parents in breeding for GRD resistance. Assessment of groundnut cropping systems used by smallholder farmers, their varietal preferences, and production challenges was done by using a field survey and participatory rural appraisal (PRA) tools. The field survey was done in Lilongwe, Mchinji and Salima while the PRA was done in Kasungu, Lilongwe, and Salima. The assessment of genetic diversity among 106 groundnut genotypes collected from ICRISAT, Chitedze gene bank and farmers was done using 19 SSR markers. High throughput DNA extraction was done followed by polymerase chain reactions (PCR) after which the amplified products were analyzed. Evaluation of genotypes to identify new sources of resistance to GRD and its aphid vector was conducted under two test situations, one with high inoculum levels and one with low inoculum levels. Under high inoculum level, the infector row technique developed by Bock and Nigam (1990) which employs a susceptible variety as a disease spreader was used. While under low inoculum level, an aphid resistant variety instead of the infector row was used to control the aphids. Aphid resistance was studied under field and glasshouse conditions. Plants were planted in rows and at 14 DAS, 2 aphids were place on each plant. Aphid resistance was determined by observing the increase in number of the aphid population on the test plants. Gene action governing inheritance of resistance to GRD was studied under high disease pressure created by using viruliferous aphids. Parents and F2 generations and their reciprocals were used in the study. The trials were laid out in a glasshouse and aphids were infested a week after germination and were killed after 7 days using Dimethoate. Disease data was collected at 7, 14, 21 and 28 days after aphid infestation. The study on groundnut cropping systems, varietal preferences and production challenges revealed that most farmers grew groundnut alongside maize (Zea mayis L.) and beans (Phaseolus vulgaris L.) as food crops and tobacco (Nicotiana tabacum L.) and cotton (Gossypium hirsutum L.) as cash crops. The most preferred groundnut varieties grown by farmers were Chalimbana and CG 7. GRD was observed in half of the fields visited. However, 98% of the farmers interviwed had experienced it in their fields at some point, and 63.3% of the farmers believed that GRD was a major problem. Other challenges noted by farmers included lack of quality seed, poor extension support, lack of inputs, manipulation of the markets by buyers, and the failure of groundnut crops to meet the high standards required by the market. The examination of genetic diversity among 106 groundnut genotypes revealed a total number of 316 alleles with a mean of 17 alleles per locus. Polymorphic information content (PIC) and gene diversity values were high, which indicated that genetic diversity among the groundnut genotypes was high. The analysis of molecular variance indicated that 72.9% of the genetic variation observed in the genotypes was due to the variation between individuals within rather than between specific population groups. The evaluation of genotypes for resistance to GRD revealed five highly resistant genotypes namely ICG 9449, ICG 14705, ICGV-SM 05701, MW 2672 and MW 2694. Farmer preferred genotypes were rated as either moderately resistant or susceptible to GRD. Aphid resistance was only recorded in ICG 12991. Yield and GRD incidence were negatively and moderately correlated, which confirmed that GRD has the potential to reduce yield in groundnuts. The highly resistant genotypes were also high yielding except for genotype ICG 9449. Farmer preferred genotypes CG 7, Chalimbana and Tchayilosi, also gave above average yields, despite high disease incidence levels, which showed that these genotypes have tolerance to GRD. The study on gene action governing GRD resistance revealed information on combining ability effects of GRD resistance. The diallel analysis showed that GCA, SCA, reciprocal, maternal and non-maternal effects were all significant, which indicated that both additive and non-additive gene effects played a role in governing GRD resistance. The significance of SCA and reciprocal effects indicated that maternal parents played an important role in the expression of GRD resistance. However, the additive effects were predominant over non-additive gene effects. Four of the resistant genotypes, ICG 14705, MW 2694, ICGV-SM 05701, and MW 2672, were the best combiners for GRD resistance. Generally, the study indicates that there is still a need to develop new varieties with resistance to GRD having traits preferred by farmers to enhance adoption. There is also a need for breeders to work with extension staff in promoting new varieties and also there is need for extension staff to actively provide information to farmers on production and marketing of groundnut. Groundnut is widely known to have a narrow genetic base which has been a bottleneck to its improvement. However, the high genetic diversity observed in this study provides a basis for selection of appropriate parental genotypes for breeding programmes which can enhance further the broadening of the groundnut genetic base. Identification of the genotypes with high resistance to GRD in this study provides an opportunity to breed more GRD resistant materials. The observation that additive gene effects are predominant in governing GRD resistance means that GRD resistant materials can be improved by introgressing additive genes using recurrent selection breeding procedures. There is also a need to employ molecular techniques which can help in shortening the entire breeding process. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2013.