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The Zambian government, through the Ministry of Agriculture and Cooperatives (MACO), provides maize seed and fertilizers to farmers at heavily subsidised prices under the Farmer Input Support Programme (FISP). MACO’s narrow evaluation of FISP, based on estimated production without quantifying the significant changes in production and other critical socioeconomic factors, fails to adequately highlight and service the benefits of subsidies to intended beneficiaries. Furthermore, MACO estimates of the impact of FISP never consider the question of how much beneficiary farmers would have produced in its absence, leading to potentially misleading assessments. The key question addressed in this study is whether using more rigorous econometric methods that account for heterogeneity in socioeconomic factors between participants and non-participants would still confirm the positive impact of FISP on maize productivity and poverty reduction, hence justifying the huge government expense on the programme. The study utilised cross-sectional data obtained from 497 randomly selected households, collected in 2011 from six provinces of Zambia to assess the causal effect of FISP on beneficiary households’ maize yields and asset accumulation. The data was analysed using well-grounded matching techniques that account for differences in observable characteristics between programme participants and non-participants. The study also tested for possible unobserved selection effects using the Rosenbaum bounds. The results indicated that participating in FISP increased maize yields and assets accumulation and hence might directly or indirectly positively affect beneficiary poverty levels. There were also no influences of unobserved characteristics on the estimated maize yield and asset level differences between participants and non-participants. On average, FISP increased maize yields by about 451 kg per hectare, with an improvement of about 0.5 on the wealth index (score used to rank households according to asset levels). The positive impact on maize yields and asset accumulation on the participating farmers therefore justifies government’s continued implementation of FISP. / Dissertation (MScAgric)--University of Pretoria, 2014. / lk2014 / Agricultural Economics, Extension and Rural Development / MScAgric / Unrestricted

M.Tech. / Fungi and their mycotoxins are major contaminants of cereals and maize which is the major staple food for Angolan population. The consumption of fungal and mycotoxins contaminated maize can induce health problems as these mycotoxins are known to induce immune suppression and other chronic diseases known as mycotoxicoses. In addition, to these mycotoxins also induce chronic diseases such as cancers of various types (liver, oesophageal, brain). Mycotoxins also immensely affect organs such as fragility and haemorrhage in tissues, liver-necrosis, bile-duct proliferation, caustic effects, intestinal haemorrhage and diarrhoea, adenomatosis, tremors, inco-ordination, mania, coma, photosensitization, sloughing of the extremities, nephrosis, uremia, infertility, prolonged oestrus, huge implications and infections in people with Human immunodeficiency virus (HIV)- AIDS. There is a very little known about the incidence of mycotoxins in Angola, which are associated with Food, Environment and Health. Therefore, the aim of this scientific novel study in history of Angola was to analyse maize samples obtained from major markets in Angola and to establish their quality with regard to mycotoxins and fungi and well as to establish possible links to the prevalent diseases as well as chronic diseases recorded among Angolan populations. To attain these aims, 60 samples of maize were randomly selected and purchased from open rural and nonregulated informal (dusty and food exposed to open air) markets around Luanda, Angola. Luanda, being the capital city of Angola was found to be the best place to sample, because of the presence of huge markets in which food products as well as maize produced in different provinces are delivered and sold to its high population. Thus, sampling in these markets was representative of the whole country and the results obtained give an approximate the status of the quality of maize consumed in different parts of Angola. The result from this study approximates the status of possible health risks that consumers can be exposed due to consumption of these mycotoxins. The samples were analysed in the Food Environmental and Health Research Laboratories at the University of Johannesburg for fungi and mycotoxins contamination using fungal screening methodologies. In terms of mycotoxins extraction, a multi-mycotoxin (solvent-solvent) extraction, solid phase extraction using SAX column for fumonisins (FBs) and immuno-affinity column (VICAM) were used for confirmation of results. Normal thin layer chromatography (TLC), reversed phase thin layer chromatography (RPTLC) (both for FBs confirmation), fluorometer “VICAM” and high performance liquid chromatography (HPLC) were techniques used for mycotoxins detection, identification and quantification. From the results obtained in this study, fungal isolation revealed contamination of the three most important toxigenic species: Aspergillus, Penicillium, Fusarium spp.

La volatilité des prix alimentaires est devenue un sujet de préoccupation constante dans les pays en développement suite à la flambée des prix des produits alimentaires en 2007/08 et 2010/11. Cette thèse s’intéresse à la caractérisation de la volatilité des prix au Burkina Faso. La volatilité des prix est définie comme la part imprévisible des variations de prix. Les objectifs de cette thèse sont en particulier i) d’évaluer les caractéristiques de la volatilité des prix du maïs au Burkina Faso, ii) d’analyser ses déterminants et iii) ses impacts sur le comportement des producteurs. Pour répondre à ces questions complémentaires, nous avons combiné des données originales et riches de prix céréaliers sur plusieurs marchés et des données sur l’activité agricole de près de 2000 producteurs sur l’ensemble du territoire Burkinabé. Plusieurs résultats émergent dans cette thèse. Premièrement, ces données ont permis d’isoler le secteur clé du maïs pour ensuite présenter de manière détaillée les données sur les prix du maïs et sur l’activité agricole des ménages utilisés dans la suite de la thèse (chapitre 1). Deuxièmement, l’analyse des séries de prix du maïs sur chaque marché propose le processus ARCH comme modèle de séries chronologiques qui explique le mieux les caractéristiques de la volatilité des prix sur la majorité des marchés. Sur ces marchés les baisses et les hausses de prix ont une contribution similaire sur la volatilité des prix, et seuls les chocs de court terme l’affectent. Les autres marchés sont caractérisés par une persistance de la volatilité avec un effet différencié des variations de prix qui s’expliquent par les caractéristiques géographiques (chapitre 2). Troisièmement, l'analyse des séries de prix en panel révèle que la volatilité des prix du maïs est élevée sur les marchés les plus enclavés (chapitre 3). Quatrièmement, l’analyse des séries de prix du maïs combinés aux données sur l’activité agricole des ménages indiquent qu’une hausse des prix du maïs accroît l'utilisation des engrais chimiques. Toutefois, les variations de prix imprévisibles diminuent le niveau d'utilisation de ces engrais ; tandis que les variations des prix prévisibles n’ont aucun effet significatif sur leur utilisation (chapitre 4). La principale originalité de cette thèse réside dans le traitement des questions relatives à la volatilité des prix à l’échelle des marchés locaux et à un niveau microéconomique avec des données de ménage, alors que cette problématique est généralement perçue sous un angle macroéconomique à l’échelle internationale. / Food price volatility is an ongoing concern in developing countries since the food price spikes in 2007/08 and 2010/11. This dissertation focuses on the patterns of food price volatility in Burkina Faso. Price volatility is defined as the unpredictable component of price variations. The aim of this dissertation is to contribute to a better understanding of three complementary issues i) the nature of maize price volatility in Burkina Faso, ii) its determinants and iii) its impacts on agricultural producers’ behavior. We combine an original database of grain prices on 28 local markets in the last 15 years and a panel database of almost 2,000 farm households’ production choices throughout the. Our results can be summarized as follows. First, these data allowed isolating the key sector of maize and then presenting detailed data on maize price series and the agricultural activity of households used in the remainder of this thesis (chapter 1). Second, the analysis of maize price series in each market suggests that ARCH model as the dominant time-series model to describe price volatility patterns in most markets in Burkina Faso. In these markets, price drops and peaks have a similar contribution to price volatility, and only recent episodes of price variations increase current volatility. Other markets are characterized by long term volatility episodes with a differential effect of price variations due to the geographical position (Chapter 2).Third, the analysis with panel method of maize price series shows that maize price volatility is greater in remote markets (Chapter 3). Fourth, by combining price series on local cereal markets and a panel data set on farm households’ production choices, we find that higher maize prices increase the quantity of chemical fertilizer use. However, unpredictable maize price variations decrease the level of fertilizer use; while predictable maize prices have no significant effect on fertilizer use (Chapter 4). The novelty of this thesis lies in the analysis of price volatility on local markets and at a micro level with household data, whereas this issue is usually perceived at the macroeconomic scale.

Philosophiae Doctor - PhD / Global climate change has resulted in altered rainfall patterns, causing annual losses in maize crop yield due to water deficit stress. Therefore, it is important to produce maize cultivars which are more drought-tolerant. This not an easily accomplished task as plants have a plethora of physical and biochemical adaptation methods. One such mechanism is the drought-induced expression of enzymatic and non-enzymatic proteins which assist plants to resist the effects of water deficit stress. The RD22-like protein subfamily is expressed in response to water deficit stress. Members of the RD22-like subfamily include AtRD22, GmRd22 and BnBDC1 which have been identified in Arabidopsis thaliana, Glycine max and Brassica napus respectively. This study aims at characterising two putative maize RD22-like proteins (designated ZmRd22A and ZmRd22B) by identifying sequence/domain features shared with characterised RD22-like proteins. Semi-quantitative and quantitative PCR techniques were used to examine the spatial and temporal expression patterns of the two putative maize Rd22-like proteins in response to, water deficit stress and exogenously applied abscisic acid in the roots and 2nd youngest leaves of maize seedlings. Using an in silico approach, sequence homology of the two putative maize Rd22- like proteins with AtRD22, GmRD22 and BnBDC1 has been analysed. Online bioinformatic tools were used to compare the characteristics of these Rd22-like proteins with those of the two maize proteins. It was shown that the putative maize RD22-like proteins share domain organisation with the characterised proteins, these common features include a N-terminal hydrophobic signal peptide, followed by a region with a conserved amino acid sequence, a region containing several TxV (x is any amino acid) repeat units and a C-terminal BURP domain-containing the conserved X₅-CH-X₁₀-CH-X₂₃-₂₇-CH-X₂₃-₂₆-CH-X₈-W motif. The putative maize Rd22-like protein appears to be localized in the apoplast, similarly to AtRD22, GmRD22 and BnBDC1. Analysis of the gene's promotor regions reveals cis-acting elements suggestive of induction of gene expression by water deficit stress and abscisic acid (ABA). Semi-quantitative and quantitative real time PCR analysis of the putative maize RD22-like gene revealed that the genes are not expressed in the roots. Exposure to water deficit stress resulted in an increase of ZmRD22A transcript accumulation in the 2nd youngest leaves of maize seedlings. ZmRD22A was shown to be non-responsive to exogenous ABA application. ZmRD22B was highly responsive to exogenous ABA application and responded to water deficit stress to a lesser degree. Transcript accumulation studies in three regions of the 2nd youngest leaves in response to water deficit stress showed that ZmRd22A transcripts accumulate mainly at the base and tips of the leaves. A restricted increase in ZmRD22A transcript accumulation in the middle of the leaves was observed. ZmRD22B showed a similar, but weaker transcript accumulation pattern in response to water deficit stress. However, ZmRD22B showed increased transcript accumulation in the middle region of the leaves. In response to exogenous ABA application, ZmRd22B exhibited high transcript accumulation at the base of the 2nd youngest leaves, with the middle showing higher transcript accumulation than the tip of the leaves. It was concluded that ZmRD22A and ZmRD22B share the domain organisation of characterised RD22-like proteins as well as being responsive to water deficit stress, although only ZmRD22B was shown to be responsive to exogenous ABA application. / National Research Foundation (NRF)

Le développement des plantes est conditionné par leurs interactions avec le microbiote racinaire, dont le fonctionnement repose sur des fonctions élémentaires partagées par plusieurs taxons, au sein de groupes fonctionnels. Certains de ces groupes incluent des PGPR (Plant Growth-Promoting Rhizobacteria), qui stimulent la croissance des plantes grâce à différentes fonctions phytobénéfiques. L'inoculation d'une PGPR peut avoir un impact sur la physiologie de la plante et sur les autres partenaires microbiens de la racine. D'ailleurs, une PGPR inoculée peut modifier la structure génétique du microbiote racinaire global, sans que l'on sache comment cet impact se concrétise au niveau de groupes fonctionnels particuliers. L'hypothèse de cette thèse est que les PGPR inoculées peuvent modifier la structure de communautés microbiennes fonctionnelles importantes pour le développement de la plante. Ces travaux ont évalué l'impact de l'inoculation de la PGPR Azospirillum lipoferum CRT1 sur la taille et/ou la diversité des diazotrophes, des producteurs d'1-aminocyclopropane-1-carboxylate (ACC) désaminase et des producteurs de 2,4-diacétylphloroglucinol (ainsi que de la communauté bactérienne totale) dans la rhizosphère du maïs cultivé en champ sous différents intrants azotés. Nos travaux ont montré que diazotrophes et producteurs d'ACC désaminase pouvaient être co-sélectionnés dans la rhizosphère du maïs, et que l'inoculation modifiait la composition taxonomique de ces groupes fonctionnels. En conclusion, l'inoculation de PGPR module la sélection rhizosphérique de taxons telluriques portant des fonctions phytobénéfiques, ce qui pourrait contribuer aux effets phytobénéfiques observés / Plant development is influenced by interactions established with root microbiota. Microbiota functioning relies on individual functions carried out by functional groups, which often contain multiple microbial taxa. Some of these groups include plant growth-promoting rhizobacteria (PGPR), which stimulate plant growth thanks to several plant-beneficial functions. PGPR inoculation may impact plant physiology and microbial partners of roots, and inoculated PGPR can modify the genetic structure of the root microbiota. However, it is not known how this impact materializes at the level of particular microbial functional groups. The hypothesis of this thesis is that inoculated PGPR will also modify the structure/composition of microbial functional groups important for plant development. This work assessed the impact of inoculation with the PGPR Azospirillum lipoferum CRT1 on the size and/or diversity of diazotrophs, 1-aminocyclopropane-1-carboxylate (ACC) deaminase producers and 2,4-diacetylphloroglucinol producers (as well as the total bacterial community) colonizing the maize rhizosphere in three fields and under different nitrogen fertilization regimes. Our work showed that diazotrophs and ACC deaminase producers could be co-selected in maize rhizosphere and that PGPR inoculation modified the taxonomic composition of functional groups. To conclude, PGPR inoculation modulates rhizospheric selection of microbial members of functional groups important for plant growth, which may mediate some of the plant-beneficial effects of PGPR inoculants

La décomposition des résidus végétaux joue un rôle essentiel dans le cycle biogéochimique des éléments nutritifs et influence le fonctionnement des écosystèmes. La composition biochimique intrinsèque des résidus végétaux est un facteur clé qui influe sur les processus de décomposition dans le sol tandis que la majorité des réactions biochimiques dans le sol, liées à la biodégradation des résidus végétaux, sont catalysées par des enzymes extracellulaires produites par les microorganismes. L'objectif global de cette étude était d'acquérir des connaissances fondamentales concernant l'impact de la qualité des résidus sur les fonctions microbiennes du sol et les modes d'intervention des enzymes du sol interviennent dans la décomposition des résidus végétaux. Cet objectif a été atteint en trois parties visant à : 1) déterminer le rôle des communautés initiales des résidus i.e. les microorganismes et leurs enzymes provenant des compartiments épiphytes et endophytes, et l'effet de la qualité des résidus végétaux sur les cinétiques des enzymes extracellulaires au cours du processus de décomposition dans le sol 2) étudier l'effet des fonctions microbiennes du sol (biomasse microbienne et enzymes extracellulaires) liées à la minéralisation sur la décomposition ultérieure de résidus introduits dans le même sol 3) explorer les interactions entre la disponibilité en azote et la décomposition des composés phénoliques par l'action des activités oxydo-réductases, et développer une méthode pour mesurer ces activités dans des sols contrastés en utilisant un seul substrat. L'approche générale de cette étude a été de sélectionner les résidus végétaux de qualité chimique variable pour obtenir des cinétiques contrastées de minéralisation du C. Le maïs (Zea mays L.) a été choisi comme plante modèle en raison de variations chimiques et structurales (Mexxal, F2, F2bm1, F292bm3) des parties aériennes (feuilles, entre-nœuds) et souterraines (racines). Des tiges de lin marqué au 13C ont été utilisées pour quantifier avec précision la minéralisation du carbone dans les différents réservoirs de carbone. Afin d'évaluer les relations entre la qualité des résidus végétaux et les fonctions biologiques associées au sol, des expériences en microcosmes contrôlés ont été réalisées en utilisant des sols agricoles et forestiers. La minéralisation du carbone, les caractéristiques chimiques des résidus (teneurs en C et N, les sucres totaux et lignine), la biomasse microbienne et les activités enzymatiques (L-leucine aminopeptidase (LAP), cellobiohydrolase (CBH-1), xylanase, cellulase et la laccase) ont été déterminées à différents stades de décomposition. Les résultats de la première étude ont indiqué que les activités de micro-organismes épiphytes et endogènes étaient du même ordre de grandeur dans le cas des racines, tandis que les activités des enzymes spécifiques (cellulase, xylanase et laccase) étaient fortement corrélées à la dégradation de leurs substrats cibles (glucanes, xylanes et lignine, respectivement). Dans la seconde étude, l'addition répétée de résidus a eu peu d'effet sur la biomasse microbienne et la dynamique enzymatique, sauf la LAP et la laccase. Ces résultats suggèrent que la qualité des résidus végétaux est le principal facteur déterminant les modes d'action de la biomasse microbienne et de leurs enzymes extracellulaires durant le processus de décomposition dans le sol. Les résultats de la dernière étude ont démontré que l'addition d'azote réprimait la minéralisation du carbone des résidus les moins lignifiés (F2, F2bm1), mais n'a pas affecté celle du résidu plus lignifié (F292bm3) au cours de la décomposition à long terme. L'ABTS est apparu comme un meilleur substrat que le L-DOPA, le pyrogallol et le TMB pour estimer les activités phénoloxydase et peroxydase.Mots clés: décomposition, biomasse microbienne, enzymes extracellulaires, qualité des résidus, maïs. / Plant residue decomposition plays a pivotal role in the biogeochemical cycling of nutrients and influences ecosystem functioning. The intrinsic biochemical composition of plant residues is a key factor influencing decomposition processes in soil while the majority of biochemical reactions in soil, related to the biodegradation of plant residues, are catalyzed by extracellular enzymes produced by microorganisms. The overall goal of this research study was to gain fundamental knowledge regarding the impact of residue quality on soil microbial functions and the principles by which soil enzymes mediate plant residue decomposition. This goal was achieved in three parts: 1) to determine the role of the initial residue community i.e. microorganisms and enzymes from the epiphytic and endophytic compartments and effect of plant residue quality on the extracellular enzyme kinetics during the decomposition process in soil 2) to investigate the effect of soil microbial functions (microbial biomass and extracellular enzymes) on the subsequent residue decomposition in the same soil 3) to explore the interactions between nitrogen availability and the decomposition of phenolic compounds through the action of oxydo-reductase enzymes activities and to develop a method to measure these activities in contrasted soils using a single substrate. The general approach of this study was to select plant residues with variations in their chemical quality to obtain contrasted C mineralization kinetics. Maize (Zea mays L.) was selected as a model plant because of variations in chemical and structural characteristics (Mexxal, F2, F2bm1, F292bm3) of aerial (leaves, internodes) and underground parts (roots). 13C-labeled flax stems were used to quantify accurately carbon mineralization in different carbon pools. To assess the relationships between plant residue quality and associated soil biological functions, controlled microcosm experiments were performed using agricultural and forest soils. Carbon mineralization and chemical characteristics (C and N contents, total sugars and lignin contents) of the plant residue, microbial biomass and enzyme activities (L-leucine aminopeptidase (LAP), cellobiohydrolase (CBH-1), xylanase, cellulase and laccase) were determined at different stages of decomposition. The results of first study indicated that activities of epiphytic and endogenic microorganisms were of the same order of magnitude in case of roots while the activities of specific enzymes (cellulase, xylanase and laccase) were highly correlated to the degradation of their target substrates (glucans, xylans and lignin, respectively). In the second study, little effect of repeated residue addition was observed on microbial biomass and enzyme dynamics except LAP and laccase. These results suggest that plant residue quality is the main factor which determines the fate/patterns of microbial biomass and their extracellular enzymes during decomposition process in soil. The results of last study demonstrated that nitrogen addition repressed the carbon mineralization of less lignified residues (F2, F2bm1) but did not affect more lignified residue (F292bm3) in long term decomposition. For estimation of phenol oxidase and peroxidase activities, ABTS appeared as a better substrate than L-DOPA, pyrogallol and TMB.Key words: decomposition, microbial biomass, extracellular enzymes, residue quality, maize.

Changing climate in combination with growing world populations mean that there is growing need for plants to be grown on land that is currently considered marginal for agriculture. Sorghum is a C4 plant that serves as an important food crop in Africa and India. It is also known to be highly drought tolerant but the mechanisms responsible for this tolerance are unclear. The overall aim of this study was to understand the drought tolerance mechanisms that enable the plant to maintain leaf function for a long time during water deficit. In Chapter 2 of this thesis, I studied the underlying physiological mechanisms for tolerating drought in two sorghum varieties with differing degrees of drought tolerance compared to a closely related species, Zea mays. During progressive drought, the more tolerant sorghum variety Samsorg 17 maintained net CO2 assimilation and photochemistry longest relative to the less tolerant Samsorg 40 and Zea mays. Differences were also seen in stomatal aperture, stomatal density, total chlorophyll content, chl a:b and A/Ci curve responses with maize more affected than the sorghum varieties. In Chapter 3, I identified novel drought tolerance mechanisms in the sorghum varieties. The less tolerant Samsorg 40 lost PsbA (D1) and Rubisco proteins and reengineered its photosynthetic apparatus to accumulate amino acids and sugars in order to maximise survival under drought. Samsorg 17 maintained photosynthetic proteins notably PsbA (D1) and Rubisco and accumulated high constitutive sugar content allowing for the maintenance of transpiration and photosynthesis. The two sorghum varieties had strikingly contrasting approaches of tolerating drought as demonstrated in Chapter 3. In Chapter 4, the aim was to characterise biochemical and metabolic changes that occur in response to drought. In particular, to identify sugars that are accumulated constitutively in Samsorg 17 and nitrogen sinks for lost N in Samsorg 40. My findings indicated a contrasting response in terms of sugar content in Samsorg 17 but support for amino acids as N sinks in Samsorg 40 as reported earlier. Sugars, sugar alcohols, lipids, organic acids, heat shock proteins and dehydrins were generally higher or more induced in Samsorg 17 relative to Samsorg 40. Samsorg 40 rather made amino acids. The implications of my findings and future work arising from this study were discussed in detail in the final chapter. In conclusion, in this thesis, it was demonstrated that closely related plants can have mechanistically different physiological and biochemical mechanisms for responding to drought.

The selection of a suitable model for efficiency analysis is one of the most important issues in policy analysis. Given the recent interest in the use of distance functions as alternative representation of production technology, this study compares the empirical performances of the parametric stochastic input distance function to its nonparametric counterpart, data envelopment analysis. A further comparison is made between the alternatives of a distance and production function frontiers. It further integrates efficiency scores from the consistent approaches in order to evaluate the performance of the sampled farm households and for analysis of policy impacts on technical, allocative and cost efficiency. The usefulness of the proposed methodology is applied to smallholder maize production in Benue State Nigeria. The maize subsector has featured in a number of Nigeria’s policy initiatives, the most current of which involves doubling of its production and productivity through promotion of improved technologies such as hybrid seed, inorganic fertilizer, pesticides, herbicides, and better management practices. Despite the policy initiatives, maize productivity has remained low raising questions about the efficiency of resource use by farmers and the benefits of Nigeria’s technology policy. The study used data obtained from a field survey for the 2008/2009 agricultural year. A multistage stratified sampling technique was employed in selection of respondents. A total of 240 maize farm households were randomly selected and interviewed using structured questionnaires. Results from all the approaches indicated considerable technical, allocative and cost inefficiency under both traditional and improved maize technology. Technical efficiency estimates range from 80 to 87 percent. Allocative efficiency estimates range from 53 to 74 percent while cost efficiency estimates range from 45 to 62 percent. The results from all the approaches indicated that inefficiency in maize production in Benue State is dominated by cost inefficiency suggesting the immense potential of enhancing production through improvement in overall efficiency. The overall consistency check shows that technical, allocative and cost efficiency measures from the three distance functions were consistent whereas similar conclusions could not hold when these were compared to the production frontier especially for technical efficiency estimates. Given the consistency of results from the parametric and non-parametric distance functions, an integrated input distance model was developed for providing final efficiency estimates and analysis of policy impacts. The results show that both traditional and improved technology users were technically, allocatively and cost inefficient. The average technical, allocative and cost efficiency are 84.2, 65.7 and 54.5 percent, respectively implying that there is a possibility of raising maize production by 45.5 percent through overall efficiency improvement. Under the integrated approach, the study revealed that hybrid seeds, inorganic fertilizer and conservation practices have positive and significant impact on farm efficiency. Other determinants of efficiency include education, age, household size, land size, credit, and membership in a farmer group. The findings justify the need for further public investment in maize technology development and proper implementation of the relevant policies in order to enhance the efficiency with which maize has been produced thereby increasing its productivity, food security and farm incomes and subsequently reducing poverty in Nigeria. / Thesis (PhD)--University of Pretoria, 2011. / Agricultural Economics, Extension and Rural Development / unrestricted

An assessment of the effect that conventional storage structures, used by smallscale farmers in northern Kwa-Zulu Natal and southern Mozambique, had on germination and vigour of maize seeds was conducted. The survey confirmed that the methods of storing the seed decreased the quality of the maize seeds. Storing maize in the field was good as a short-term solution as initial germination was 100%. Following storage at suboptimum conditions, germination dropped to 25.3%. Commercially treated maize seeds were compared to the test samples collected. After storage, the commercially treated seeds maintained a germination percentage above 75. Untreated maize seeds were treated with fungicides at the recommended dosages. Thereafter the seeds were subjected to germination and vigour tests according to methods outlined by the International Seed Testing Association. All treatments maintained percentage germination above 75. Apron® XL had the highest percentage germination of 83. This trend was also found following the cold test and greenhouse emergence. None of the treatments differed significantly from the control. In this study none of the treatments caused major imbibition damage as indicated by the percentage weight increase and the low leachate conductivity (1012-1271 ìScm-1g-1). The effect of accelerated ageing (AA, 2 and 4 days) and long-term storage (3 and 6 months) on germination and vigour of treated maize seeds was investigated. In the untreated control and treatments there was a gradual decrease in germination following ageing and storage of the seeds. Apron® XL failed to germinate after 3 months. The decrease in germination was mirrored by the leachate conductivity readings. Thiram was the only treatment to maintain germination after 6 months storage. The seeds were planted in two greenhouse trials to assess the performance of the treatments in vivo. The first trial evaluated the emergence and second the emergence and control of Fusarium graminearum. Results from the first trial showed that following 2 d AA, seeds treated with Thiram had the highest percentage emergence (70.7) followed by Celest® XL (68) and the untreated control (62.7). Following inoculation, a similar trend was seen for the treatments and the untreated control. In relation to the percentage seedlings emerged, the control had the highest percentage diseased seedlings. Celest® XL had the lowest percentage diseased seedlings (10, 2 and 1) but failed to germinate after 6 months storage. Thiram was the only treatment to emerge after 6 months storage. The ultrastructural changes in embryonic roots of the untreated control, Celest® XL and Apron® XL were investigated using transmission electron microscopy. These seeds were subjected to 48 hr rapid imbibition and 2 d AA. The most obvious difference between the untreated control, Apron® XL and Celest® XL was the number and position of the vacuoles. In contrast the lipid layer was still attached to the cell wall in the Apron® XL and Celest® XL treatments but in the untreated control they appeared more concentrated in the cytoplasm. This study proved that Thiram was the best treatment among the fungicides tested. However, these results need to be confirmed using a larger range of maize seed lots. / Thesis (PhD)--University of Pretoria, 2011. / Microbiology and Plant Pathology / unrestricted