Made available in DSpace on 2017-05-12T14:48:18Z (GMT). No. of bitstreams: 1 Marcia_texto.pdf: 2638877 bytes, checksum: 43437bc40d15ec7df358c7a26ec72a0a (MD5) Previous issue date: 2011-06-18 / One of the biggest problems in the production of soya is to get a vigorous seed that can emerge under wide range of conditions in the field. If some factor threatens seed germination and seedling emergence, it threatens also the stand of crop. Thus, the objective of this work was to compare the tests used to identify vigor in soybean seeds relating after comparison, tests that can be used with lower cost and faster results, and establish a model that correlates seeds vigor given in the laboratory with field emergence. The work was conducted at the Laboratory for Seeds and Plants Evaluation (LASP), Unioeste - Campus Cascavel and in field at the COODETEC Central Cooperative for Agricultural Research, in Cascavel. Soybean seeds were harvested with mechanical harvesters. Five cultivars of soybeans produced in crop year 08/09 from COODETEC, under the same conditions of management and harvesting and with different morphological characteristics were used. The tests used included determination of moisture content, germination, emergence in sand, purity, immersion in sodium hypochlorite, accelerated aging, controlled deterioration, cold test, seedling growth, electrical conductivity, tetrazolium, emergence percentage and seedling length in field and seedling dry weight. The experimental design used for tests was randomized and the resulting means were compared by the Tukey test at 5% significance level. It was observed from the results that the three cultivars that stood out in most of tests also showed better field emergence. Among the analyzed tests, it can be concluded that the controlled deterioration, tetrazolium, purity, germination speed index emergence speed and emergence speed coefficient in sand showed closer to the emergency response in field. A multiple regression model was then adjusted to account for the emergence in the field, which included the emergence speed in sand (ES), the germination speed index (GSI) and the emergence speed index in sand as variables correlating better seed vigor with field emergence. / Um dos maiores problemas na produção de sementes de soja é obter uma semente vigorosa que possa emergir sob larga faixa de condições no campo. Se algum fator compromete a germinação das sementes e a emergência das plântulas, compromete, também, o estande da cultura. Dessa forma, o objetivo deste trabalho foi comparar testes utilizados para a identificação de vigor em sementes de soja, relacionando, após a comparação, testes que possam proporcionar resultados mais rápidos, e estabelecer um modelo que correlacione o vigor das sementes determinado em laboratório com a emergência em campo. O trabalho foi realizado no Laboratório de Avaliação de Sementes e Plantas (LASP) da Unioeste campus de Cascavel e em campo, na COODETEC Cooperativa Central de Pesquisa Agrícola, no município de Cascavel. Foram utilizados cinco cultivares de soja, produzidos no ano agrícola 08/09, oriundos da COODETEC, sob iguais condições de manejo e colheita (mecânica) e com características morfológicas diferenciadas. Os testes empregados foram determinação do teor de água, germinação, emergência em areia, pureza, imersão em hipoclorito de sódio, envelhecimento acelerado, deterioração controlada, teste de frio, crescimento de plântulas, condutividade elétrica, tetrazólio, porcentagem de emergência e comprimento das plântulas no campo e massa seca de plântula. O delineamento experimental, utilizado para os testes foi inteiramente casualizado e as médias foram comparadas pelo teste de Tukey a 5% de probabilidade. Observou-se a partir dos resultados que as três cultivares que se destacaram na maioria dos testes, também apresentaram melhor emergência em campo. Dentre os testes analisados pode-se concluir que envelhecimento acelerado, deterioração controlada e tetrazólio, apresentaram respostas mais próximas a emergência em campo. Pela análise de correlação pode-se concluir que as melhores correlações com emergência em campo foram observadas pelos testes de deterioração controlada, velocidade de emergência em areia, coeficiente de velocidade de emergência em areia, envelhecimento acelerado, índice de velocidade de germinação e tetrazólio para sementes sem danos. O modelo de regressão múltipla ajustado para explicar a emergência em campo contemplou a velocidade de emergência em areia (VE), o índice de velocidade de germinação (IVG) e o índice de velocidade de emergência em areia (IVE), como variáveis que correlacionam melhor o vigor das sementes com a emergência em campo.

Diversos são os direcionadores para a atenção mundial na adoção dos biocombustíveis. Elevados preços do petróleo e aquecimento global figuram entre os principais. Sob esse cenário, vários países investem em pesquisas para encontrar uma fonte de energia limpa produzida em um contexto sustentável. Entre elas está o biodiesel obtido dos óleos vegetais. No Brasil, após a institucionalização da mistura em janeiro de 2008, destacouse a necessidade de realizar estudos aprofundados na seleção da melhor matéria-prima destinada à manutenção do programa brasileiro, além de estabelecer novas áreas de produção que atendam, simultaneamente, a inserção do pequeno agricultor e a produção equilibrada com os alimentos. A produtividade por hectare é identificada a priori como relevante, de modo que este estudo considerou as culturas do dendê e do pinhão-manso como matériasprimas, bases à viabilidade de produção do biodiesel no Brasil. O semi-árido brasileiro foi escolhido devido às grandes extensões de terra produtivas, mas inativas, e aos incentivos federais que proporcionam uma vantagem competitiva no Ambiente Institucional. A metodologia de pesquisa fez uso conjunto da Fenomenologia e dos Estudos de Caso, aplicando a análise na região do Vale do São Francisco. Para a condução da pesquisa foi utilizada a base de dados primários e secundários. O ambiente de pesquisa fez uso do ambiente de campo e do estudo simulado dos dados em planilhas eletrônicas. Os resultados obtidos destacaram o fator produtividade por área plantada e teor de óleo por peso da cultura como dois importantes condicionantes para a viabilidade de produção do biodiesel, além da integração das atividades agrícola e industrial. O estudo finaliza, comprovando a viabilidade de implantar um SAG do Biodiesel na região semi-árida brasileira, fazendo uso das áreas irrigadas e das áreas de sequeiro. / There is a wide guidance to the world\'s attention in the adoption of biofuels. High oil prices and global warming are among the main ones. Under this scenario, several countries have invested in research to find a source of clean energy produced in a sustainable context. Among them is biodiesel made from vegetable oils. In Brazil, after the institutionalization of the mixture in January 2008, the need to conduct studies in the selection of the best raw material for the maintenance of the Brazilian program was highlighted, in addition to establish new areas of production that meet both the insertion of small farmers and balanced production along with food. The yield per hectare is taken as relevant, so this study has taken in account the crops of palm and jatropha curcas as raw materials, considering the feasibility of producing biodiesel in Brazil. The Brazilian semi-arid was chosen because of the large area of productive, but inactive land and federal incentives that provide a competitive advantage in the Institutional Environment. The research methodology made use of all Phenomenology and Case Studies by applying the analysis in the Valley of San Francisco River. To conduct the research, a basis for primary and secondary data was used. The research environment made use of field environment and simulated study of data in spreadsheets. The results highlighted the factor productivity per planted area and oil content by weight of crop as two major constraints to the feasibility for biodiesel production, in addition to the integration of agricultural and industrial activities. The study ends, proving the feasibility of settling a Biodiesel SAG in the semiarid region in Brazil, using irrigated and dry areas.

Thesis (M. A. Agricultural Management (Agricultural Extension)) -- University of Limpopo, 2019 / Smallholder farmers’ need for regular supply of adequate, quality and affordable seed led to the establishments of Community-Based Maize Seed Production Schemes (CBSPSs) in most developing countries, including South Africa. In view of the important influence of perception on the adoption and continued use of an innovation, this study was undertaken to evaluate farmers’ perceptions of CBSPSs in Polokwane and Lepelle-Nkumpi Local Municipalities of Limpopo province. The conceptualization of perception used in this study was based on the Düvel (1991) framework. The evaluation focused on whether planting the scheme’s main product, improved Open-Pollinated Varieties (improved OPV maize) seed meets farmers’ needs based on their perceptions and the extent of farmers’ planting of improved OPV maize. A census approach was used in view of the small numbers of seed producers in the schemes; all scheme members (50) were, therefore, interviewed between 27 March and 21 April 2017. To allow for comparison, an equal number of farmers (50) who were not members of the scheme were also interviewed. Data was collected from farmers using a semi-structured questionnaire. Descriptive and inferential statistics were applied to analyze the data using SPSS software. A binary logistic model was used to analyze factors that influence farmer perceptions on OPV benefits. The study findings showed that there is a significant relationship between awareness knowledge of improved OPV maize and planting of improved OPV maize. Furthermore, the results showed that farmers perceptions of the advantages and disadvantages of improved OPV maize seed were not different among scheme and non-scheme members as they were all in agreement that improved OPV maize have more benefits than their own previously recycled seeds. Finally, findings showed that respondents municipality and scheme membership had a significant, effect on the positive perception of planting improved OPV maize seeds. Other explanatory variables such as sex, farming experience, years of viii schooling, farm size, income and age of participants had no significant effect on farmer perceptions. It is therefore recommended that improved OPV maize be made widely available and promoted based on its advantages to enhance its adoption. Future studies on these seed schemes could look into the production and financial analysis of CBSPSs to ascertain their profitability and sustainability. / Agricultural Research Council (ARC)

We explored the seasonal factors that might play a role in triggering germination of Dendromecon rigidaand Ehrendorferia chrysantha.D. rigida and E. chrysantha have been found difficult to germinate using common greenhouse techniques, Keeley and Fotheringham successfully germinated both species after storing their seeds in the field over a year and treating them with smoke. Identifying the specific seasonally changing factors that stimulated germination could have implications for understanding germination requirements for these and other hard-to-germinate chaparral species. Dendromecon rigidaand Ehrendorferia chrysanthaare part of the Papaveraceae family and both are found in the chaparral environment in Southern California. Both species are known to increase in numbers after fire events. Both are believed to have morphophysiological dormancy based on their miniscule embryo and increase in seedling presence after fire events. Climate within the chaparral environment consists of hot, dry summers and cold, wet winters. Storing seeds of D. rigidaand E. chrysantha in the field over winter and spring months resulted in increasing germination for D. rigida seeds that were imbibed in smoke-water. Germination of D. rigidaseeds occurred within six weeks and no further germination was noted beyond that. Ehrendorferia chrysanthaseeds failed to germinate in the field. Lab studies tested effects of stratification at different temperatures (5ºC, 10ºC, 18ºC, 25ºC and 30ºC), stratification for different durations (0, 2, 4, 8, and 12 weeks), heat-shock, and fluctuating moisture and temperature conditions on a weekly time scale, on germination of both species. Of all these treatments the only combination that was effective in germinating seeds of D. rigidaand E. chrysanthawas warm stratification at 30ºC for 8 weeks following smoke-water imbibition. Under these conditions seeds of D. rigidaand E. chrysanthagerminated to 10% and 9.3%, respectively. Further studies on D. rigidaindicated a stratification temperature optimum between 30-40ºC with germination increasing with lack of light. These tested conditions corresponded to the daily peak soil temperatures measured at shallow depth in an area of chaparral inhabited by D. rigida. The period immediately after the first rain event after a fire may provide the chemical cues and warm stratification required to germinate buried seeds in this species.

Graduation date: 2005

Hemp seed proteins (HSP) were investigated for physicochemical and functional properties in model food systems. In addition, the HSP were enzymatically digested and the released peptides investigated as potential therapeutic agents. Membrane isolated HSP (mHPC) were the most soluble with >60% solubility at pH 3-9 when compared to a maximum of 27% for isoelectric pH-precipitated proteins (iHPI). However, iHPI formed emulsions with smaller oil droplet sizes (<1 µm) while mHPI formed bigger oil droplets. The iHPI was subjected to enzymatic hydrolysis using different concentrations (1-4%) of six proteases (pepsin, pancreatin, flavourzyme, thermoase, papain and alcalase) to produce various HSP hydrolysates (HPHs). HPHs had strong in vitro inhibitions of angiotensin converting enzyme (ACE) and renin activities, the two main enzyme systems involved in hypertension. Oral administration of the HPHs to spontaneously hypertensive rats led to fast and persistent reductions in systolic blood pressure. The HPHs also inhibited in vitro activities of acetylcholinesterase (AChE), a serine hydrolase whose excessive activities lead to inadequate level of the cholinergic neurotransmitter, acetylcholine (ACh). Inadequate ACh level in the brain has been linked to neurodegenerative diseases such as dementia and Alzheimer’s disease (AD); therefore, AChE inhibition is a therapeutic target. The 1% pepsin HPH was the most active with up to 54% AChE inhibition at 10 µg/mL peptide concentration. The 1% pepsin HPH (dominated by <1 kDa) was subjected to reverse-phase HPLC peptide purification coupled with tandem mass spectrometry, which led to identification of several peptide sequences. Some of the peptides inhibited activities of both animal and human AChE forms with LYV being the most potent against human AChE (IC50 = 7 µg/ml). Thus the LYV peptide may serve as a useful template for the development of future potent AChE-inhibitory peptidomimetics. In conclusion, several novel AChE-inhibitory peptides were discovered and their amino acid sequences elucidated for the first time. Results from this work identified HSP products that could serve as functional ingredients in the food industry. The work also produced and confirmed the in vitro AChE-inhibitory activities of several new peptide sequences that may serve as therapeutic agents for AD management. / October 2015

Maize grain contains high levels of phytic acid which chelates iron, zinc and other micronutrients as it passes through the digestive systems of monogastric consumers reducing their bioavailability. Breeding for low phytic acid (LPA) content to improve micronutrient bioavailability is hampered by a tedious and destructive colorimetric method on the grain, low yields compared to the wild-types and reduced seed germination and vigour of LPA mutants. Breeding for LPA therefore should also incorporate breeding for improved germination and vigour in the mutants. Molecular markers to speed up the selection process and studies on gene action and combining ability for germination, vigour and yield parameters of the LPA mutants in combinations with other different maize germplasm will speed up breeding for this trait. The objectives of this study were: to develop a molecular marker linked to the lpa1-1 gene and apply this marker for foreground selection in a backcross breeding programme and to use amplified fragment length polymorphism (AFLP) markers for background selection to recover the recurrent parent genome to speed up the backcrossing process; to study gene action and combining ability for seed germination, vigour and yield from diallel crosses involving LPA mutants, QPM and normal endosperm maize inbred lines by replicated laboratory seed tests ( standard germination test and accelerated aging test) and field evaluations in South Africa and Zimbabwe. A co-dominant single nucleotide polymorphism (SNP) marker which detects the transition base change of C/T nucleotides was developed from the gene sequence to identify the lpa1-1 trait. The 150 bp lpa1-1 SNP marker was validated by forward and reverse DNA sequencing of the parental amplification products which confirmed the C to T base change resulting in the LPA phenotype. The lpa1-1 SNP marker was used for foreground selection in 250 BC(2)F(1) progenies of CM 32 (LPA) x P 16 as the recurrent parent. This SNP marker was used to genotype the lines into homozygous dominant (wild type) and homozygous recessive (LPA) genotypes by their melting profiles and heterozygous genotypes by the normalised difference plots using high resolution melt (HRM) analysis. Seventeen heterozygous and 11 homozygous recessive lines were identified for background selection by fingerprinting with AFLP markers to determine the amount of recurrent parent (P 16) genome present. There were six EcoRI/MseI primer combinations tested with 277 data points scored (84% polymorphism rate). The amount of recurrent parent (P 16) genome recovered ranged from 62% to 92% with 13 lines showing greater than 83% of the recurrent parent genome. The effects of diallel crosses generated between four LPA, three QPM and three normal endosperm maize lines were determined for seed germination and vigour using the standard germination and accelerated aging seed tests under laboratory conditions in accordance with the procedures of the International Seed Testing Association. The specific combining ability (SCA) effects and general combining ability (GCA) effects were significant for the seed germination and vigour traits, indicating that genes with non-additive and additive effects were important in controlling these traits. However, the SCA effects were greater than GCA effects suggesting that genes with non-additive effects were predominant. The LPA parents showed reduced vigour compared to the normal and QPM inbred lines under both conditions, with LPA lines CM 31 and CM 32 showing stress tolerance. There were some combinations involving LPA lines, such as LPA x normal, LPA x QPM and LPA x LPA that retained high vigour and high germination rates under accelerated aging conditions, suggesting that they could be stress-tolerant.. A 10 x 10 diallel involving four LPA, three QPM and three Nm inbred lines was evaluated in replicated trials across six environments. Results show that both additive and non-additive gene effects were significant for resistance to northern corn leaf blight (NCLB), grey leaf spot (GLS) and Phaeosphaeria leaf spot (PLS) diseases. The additive gene effects were predominant for the yield and associated secondary traits such as days to mid-pollen shed (DMP), days to mid-silking (DMS), ear per plant (EPP) and grain moisture content (GMC) and grain yield. The LPA lines were early flowering and had quick grain dry down rate but all showed undesirable negative and significant GCA effects for yield. The yield of the LPA x LPA, LPA x Nm and LPA x QPM group of crosses was lower than the check hybrids by about 32 to 67% showing the need for yield improvement of the LPA combinations. An eight x eight diallel involving two LPA and six normal endosperm lines was evaluated over two seasons in five locations with two replications for grain yield components and foliar diseases. There was significant additive and non-additive gene action for both seed germination and vigour traits with predominance of non-additive gene effects. Both additive and non-additive gene effects were significant for yield and associated traits such as anthesis dates and number of ears per plant. However, the additive gene action was predominant for yield and associated traits. Generally the LPA lines and their combinations showed lower germination and vigour. The LPA line, CM 32 showed stress tolerance under accelerated aging conditions. There were three LPA x Nm crosses that showed improvements to the means of seed germination and vigour and yield traits. Results indicated that there was not any significant correlation between yield and seed germination and between yield and vigour. Yield was, however, significantly and positively correlated with anthesis dates and GMC, indicating that higher yield was associated with longer growing cycles. This study was able to successfully develop and apply the lpa1-1 SNP marker for foreground selection and AFLP markers for background selection in a backcross breeding programme. Problems of low seed germination, seedling vigour and grain yield of LPA lines and their combinations were confirmed. However results also indicated some potential of combining the LPA and QPM traits in a single cultivar. In general, procedures such as reciprocal recurrent selection, that emphasise both GCA and SCA effects would be recommended to improve seed germination, seedling vigour and yield in developing varieties with LPA trait. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2010.

This study investigates the characteristics of technology adoption by small-scale farmers, notably the factors influencing the adoption of hybrid maize seed, inorganic fertilizer and machinery technologies. The study also on the basis of socio-economic and institutional factors, identifies the dimensions of small-scale farmers. Data for the study were obtained from a sample survey of 160 households in the Amangwane and Amazizi wards, located in the Okhahlamba magisterial district of KwaZulu-Natal during August 2000. The chief aim of this study is to generate empirical information that can be used to devise programs to encourage small-scale farmers to adopt agricultural technologies. The motivation of the research emanates from the fact that there is limited empirical information as to the actual adoption patterns of agricultural technologies by small-scale farmers. The nature and relative importance of factors associated with technology adoption is time and location specific. The study by using more recent and broader information builds on previous studies in order to complement technology adoption research on small-scale farmers. Understanding what factors influence the adoption of farm technologies and categories or dimensions of small-scale agriculture should provide information on policy options to stimulate technology adoption and improve growth in agricultural productivity. A categorical dependent variable was specified to identify farmers' adoption pattern of hybrid maize seed and fertilizer. Seventy-two farmers were adopters of both hybrid seed and fertilizer, 56 were adopters of either hybrid seed or fertilizer while 32 farmers were non-adopters. The results of binary logistic regression analysis indicate the adoption of hybrid maize seed and fertilizer is positively associated with, in order of importance, larger farms, older household heads, more value of livestock and better access to information sources. An index that indicates farmers' status of adoption of machinery technologies was constructed using a principal component analysis technique. The analysis showed that the adoption of machinery technologies can be represented by the single index which could be used as a dependent variable. A principal component regression analysis was subsequently used to determine factors contributing to the adoption of the machinery technology index. The results indicate that adoption was higher for (1) older and male headed households in general and residents of the Amangwane ward in particular; (2) operators of more arable land, owners of more livestock and earners of more non-farm income; and (3) households with large family labour, and households that made use of extension services and information sources. These results are consistent with hypothesised relationship between technology adoption and the predictors and are supported by previous empirical findings. Priority should be given to policies that alleviate the tenure insecurity problem on arable land and this in turn promotes a land rental market. This would involve an institutional change and legal infrastructural support services. Arable land holding is highly skewed within the communal setting and the state needs to address this equity issue on arable land through redistribution or reform policies. The state needs also to invest in public goods that alleviate the problems of private investors for example by encouraging credit providers or promoting rural financial markets to alleviate liquidity constraints and enhance adoption. Investment in farmer training and education should therefore, be seen as priority if higher adoption rates and an improvement in income are to be achieved. Inadequate and poor extension and information services imply an urgent need for the formation of community and farming associations and for the provision of extension services to groups of farmers. Investment in these areas may reduce the cost of technology transfer programmes. The results of a principal component analysis to identify the dimensions of small-scale farmers in communal areas of KwaZulu indicate that farmers fall into distinct categories. Component 1 is an emerging commercial and a more mechanised household while component 2 is a land-less farm household that is more educated and earns more non-farm income largely from contractor services. Component 3 is a non-farm female headed household that depends on income from land renting and non-farm jobs. Component 4 is a small intensive garden farmer, headed by a relatively educated female who has access to institutional services. Component 5 is relatively less educated, a female-headed and land-poor household that rents land and produces intensively. It is concluded that a single policy measure cannot do justice to the needs of all of the farmers since it would affect different households differently. An integrated and a comprehensive programme is needed that would promote agriculture; facilitate income transfer or safety nets to alleviate poverty and the relief of short-term stress; address the problems of tenure insecurity; overcome the gender inequalities in accessing resources; and restructure institutional supports by providing rural finance, and an extension and legal infrastructure. / Thesis (M.Sc.Agric.)-University of Natal, Pietermaritzburg, 2001.

Transverse cotyledonal cracking (TVC) was characterised at physiological, biochemical and molecular levels in three common bean (Phaseolus vulgaris L.) cultivars: Imbali, Tongaat and Tokai. The incidence of TVC was determined visually on ten-day old seedlings and was expressed as the number of cracks per plant. The effect of Ca++ on TVC incidence was examined by enhancing the calcium content of seed cotyledons using calcium salts in seed priming and coating. EDAX was used to quantify the cotyledonal calcium content. Activities of the pectinolytic enzymes polygalacturonase (PG) and pectin methylesterase (PME) were assayed at dry seed, VC, R4 and R6 phenophases of the bean plant, and zymogram electrophoresis was used to identify the two enzymes. The results showed that cultivars Imbali, Tongaat, and Tokai were susceptible resistant and intermediate, respectively, with respect to TVC incidence. Calcium uptake was higher in Tongaat cultivar (P= 0.05) compared with Imbali and Tokai, irrespective of calcium salt enhancement. Vigour was significantly reduced (P< 0.01) by both coating and priming. TVC significantly lowered yield (P= 0.05) in the susceptible Imbali cultivar. Zymogram analysis identified lytic bands at ~45kDa (PG gel) and ~30kDa (PME gel). The activity profile of PME was similar for all cultivars. However, PG activity of susceptible Imbali was high in dry seeds and at the R4 and R6 stages of plant development, whereas the more resistant cultivars displayed high activity at the VC stage only. It is concluded that high PG activity at R4 stage is a more reliable determinant of green bean propensity to cotyledonal cracking. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2005.

Sunflower (Helianthus annuus L.) is one of the most important oil crops in South Africa and genetic improvement for grain yield and oil-content was initiated in the country in the early 1970s. Commercial production of sunflower in South Africa is done under natural rainfall conditions in areas where frequencies of drought are high hence the requirement for drought tolerant cultivars. An assessment of the genetic gains in seed and oil yield achieved since 1970, the effects of re-cycling inbred lines and strategies for developing drought tolerant sunflower cultivars has not been done for South African sunflower breeding programmes. Two data-sets were used for the genetic gain studies: side-by-side evaluation of historical and current sets of popular cultivars in the same environment under one set of trial management practices; and yield trends in commercial farmers’ fields based on annual production estimates. The estimated relative genetic gain for seed yield based on side-by-side trials was 1.5% year−1 and the relative gain in seed yield per year under commercial production was 1.9% year−1. The contribution of new cultivars to total seed yield progress in sunflower were 56.3% for the period 1970 to 1989; 23.9% from 1990 to 2009 and the mean over the four decades under consideration from 1970 to 2009 was 41.6%. Quantifying the usefulness of inbred lines in advanced cycle plant breeding was done using four base breeding populations based on: phenotypic or genetic variability; heterosis; and combining ability. Significant genetic variation was evident for seed yield and oil yield while genetic variability for oil content was low. Genetic advance (GA%), with a 10% selection intensity, was high for seed yield and oil yield for each of the four populations ranging from 36-42% and 38-43%, respectively. The GA% for oil content was low ranging from 1.3% to 5.1% indicating the need to introgress high oil content germplasm in the present breeding populations in advanced cycle pedigree breeding. Founder parent heterosis (FPH), mid-standard heterosis (MSH) and high standard heterosis (HSH) indicated that some new testcross hybrids from the advanced cycle pedigree breeding populations were performing better than their founder parents in hybrid combination as well as the standard commercial hybrid checks. From variance component analysis, general combining ability (GCA) was predominant over specific combining ability (SCA) for seed and oil yields indicating that superior hybrids can be identified based on positive and significant GCA effects of the female lines. For oil content, SCA was predominant over GCA indicating that it would be best to select for specific hybrids combinations with high oil content rather than selecting female lines with high GCA effects. Variable moisture conditions characterise the sunflower production environments in South Africa. Breeding for such environmental conditions requires a combination of strategies including use of secondary traits and developing appropriate test environments. Three secondary traits, head diameter, stem diameter and stay green canopy which are easy to measure in the field were evaluated for their appropriateness for selecting for drought tolerance under three moisture conditions: random stress environments (RSE), managed drought stress environments (MSE) and well watered nonstress environments (NSE). Type A genetic correlations indicated that stay green canopy (SG) had the potential to be used as secondary trait to indirectly improve oil yield under the three moisture conditions. The indirect selection efficiency (ISE) for SG using genetic correlations based on H2 were 0.79, 0.82 and 0.78 in the RSE, MSE and NSE, respectively, while that using genetic correlation based on h2 were 0.67, 0.98, and 0.93 in the RSE, MSE and NSE, respectively. In both cases selection in the MSE had the highest efficiency using genetic correlations based on either H2 or h2. Estimates of indirect selection based on type B genetic correlations indicated that indirect selection for oil yield (OY) in the MSE and NSE for the target RSE was as effective as direct selection of OY in the RSE based on additive genetic correlations of 0.96 obtained in both selection environments. Overall, the results from the exploratory drought tolerance study should inform the development of breeding strategies to improve drought tolerance and associated yield stability of sunflower cultivars grown in South Africa and associated environments. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2013.