The first serious outbreak of brown rust of sugarcane caused by Puccinia melanocephala Syd. & P. Syd. was reported in India in 1907. It was first reported in South Africa (SA) in 1941 on the variety Co301 and is now present in almost all the sugarcane growing areas of the world. In SA, it is now described as an important disease of sugarcane, causing yield losses of up to 26% in susceptible varieties. Within the SA sugar industry, rust is controlled through the use of resistant varieties as it is the most economical method of control. However, most of the newer varieties that are being released have an intermediate resistance rating for rust. An integrated management approach for the control of rust is therefore being investigated. Aspects investigated in this study included environmental conditions required for development of the disease i.e. epidemiology, the use of silicon (Si) as a cultural control method against brown rust and identification of gene sequences expressed in response to brown rust infection. For the epidemiology study, inoculated plants were incubated in a dew chamber at different temperatures and leaf wetness periods. The choice of leaf wetness duration and temperature was based on urediniospore germination studies. The optimum temperature for urediniospore germination and disease development at > 98% relative humidity was found to be between 20 and 25°C with nine hours of leaf wetness. Silicon has been shown to reduce the incidence of diseases and pests in a number of crops. The ability of sugarcane to accumulate Si and the location of Si deposition was established using two uptake and deposition trials. Different concentrations of Si were applied to the plant and accumulation in the roots, stalks, old leaves and young leaves was determined using inductively coupled plasma optical emission spectrometry, with accumulation found to be roots > old leaves > stalks > young leaves. Silicon deposition in the leaves was determined using energy dispersive X-ray mapping on freeze dried specimens and significant differences were found between the upper epidermis, lower epidermis and mesophyll with the most Si being deposited in the lower epidermis. For disease severity, plants were naturally infected with rust and rated weekly. A significant decrease in disease severity and area under disease progress curve was noted when the Si concentration increased, indicating that Si has potential in reducing rust incidence. Currently, the most reliable and economical method of managing brown rust is with the use of resistant varieties. Identification of resistance within breeding lines is therefore important. For this part of the study, suppression subtractive hybridization was used as a tool to identify differentially expressed genes between a susceptible and resistant variety and a susceptible and intermediate variety, in response to brown rust infection. Two efficient subtracted cDNA libraries were generated and differentially expressed sequences were identified within each library. The results of this study show potential for the development of molecular markers which could be used for the early identification of brown rust resistance during the breeding process. This study forms a firm basis on which an integrated management strategy, for the management of brown rust in the SA sugar industry, could be designed. The cDNA sequences identified could be further investigated and used to develop molecular markers to select for rust resistant varieties, the epidemiology results together with further field data could be used to develop a disease prediction model and Si has potential in the field to reduce brown rust severity. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2009.

A agroindústria sucroenergética tem importância histórica no agronegócio brasileiro e vivenciou um período de grande desenvolvimento e transformações nas últimas décadas, o que, consequentemente, impactou de maneira diversa sobre o mercado de trabalho da atividade. Neste contexto, diversos estudos buscaram avaliar a evolução de indicadores do mercado de trabalho da agroindústria sucroenergética, destacando sua dimensão, transformações e relevância. Porém, ainda se identificam lacunas pouco exploradas pela literatura científica, como o impacto de transformações institucionais e conjunturais no mercado de trabalho do setor, advindos principalmente da restrição às queimadas no processo de colheita e do período de crise na atividade. Posto isso, este trabalho de tese busca contribuir neste campo de estudo, com dois capítulos independentes, ambos tendo como argumento principal a avaliação das mudanças institucionais e conjunturais do setor sucroenergético ao longo dos últimos anos, com destaque aos efeitos sobre o mercado de trabalho formal da atividade. No primeiro, adentra-se à discussão de maneira mais ampla, avaliando-se a evolução dos indicadores do mercado de trabalho formal dos setores de cana-de-açúcar, açúcar e etanol para o período de 2000 até 2016. Também são calculadas equações de rendimento, de modo a se obter informações sobre os determinantes do nível de salário dos trabalhadores do setor sucroenergético. Como resultados principais, verifica-se a grande expansão do número de empregos e salários até 2008, com diferenciais de salários entre os trabalhadores do setor, em geral, apresentando redução. Mas, houve queda no número de ocupações no período imediatamente posterior, até 2016, mas com crescimento da qualidade das ocupações. Destacou-se também o processo de mecanização da colheita que impactou na redução significativa de empregos na área agrícola. Também se verificaram efeitos da crise do setor, que teve influência expressiva principalmente na queda de empregos na indústria entre 2008 e 2016. No segundo estudo, busca-se uma análise mais específica dos efeitos destas mudanças institucionais e conjunturais sobre o mercado de trabalho formal do setor sucroenergético, lançando-se foco específico sobre os fluxos de contingente de trabalhadores relacionados à atividade, avaliando-se fluxos de migração e a realocação dos trabalhadores entre atividades e localidades no período de análise de 2008 e 2016, com o uso da metodologia de redes socioeconômicas e clusters. Como resultados principais, verifica-se a saída do mercado formal de um grande contingente de trabalhadores, com característica majoritária de baixa escolaridade, o que evidencia a dificuldade de trabalhadores do setor em se realocar de maneira formal em outras atividades. / The sugarcane agroindustry has historical importance in Brazilian agribusiness and has experienced a period of great development and transformation in the last decades, which, consequently, had a different impact on the labor market of the activity. In this context, several studies sought to evaluate the evolution of indicators of the labor market of the sugarcane agroindustry, highlighting its size, transformations and relevance. However, there are still gaps that are not explored by the scientific literature, such as the impact of institutional and conjunctural changes in the labor market of the sector, mainly due to the restriction to the burnings in the harvesting process and the period of crisis in the activity. Thus, this thesis aims to contribute in this field of study, with two independent chapters, both having as main argument the evaluation of the institutional and conjunctural changes of the sugarcane industry in recent years, with emphasis on the effects on the formal labor market of the activity. In the first, a broader discussion is introduced, evaluating the evolution of the formal labor market indicators of the sugar cane, sugar and ethanol sectors for the period from 2000 to 2016. Income equations are also calculated, in order to obtain information about the determinants of the wage level of workers in the sugar-energy sector. The main results are the great expansion in the number of jobs and wages up to 2008, with salary differentials among workers in the sector, in general, showing a reduction. However, there was a decrease in the number of occupations in the period immediately after, until 2016, but with growth in the quality of occupations. It was also highlighted the mechanization process of the harvest that impacted on the significant reduction of jobs in the agricultural area. There were also effects of the sector\'s crisis, which had a significant influence mainly in the fall of jobs in industry between 2008 and 2016. In the second study, a more specific analysis is sought of the effects of these institutional and conjunctural changes on the formal labor market of a specific focus and on the contingent flows of workers related to the activity, assessing migration flows and the reallocation of workers between activities and localities in the period of analysis of 2008 and 2016. As main results, the formal market exit of a large contingent of workers, with a majority of low schooling, evidencing the difficulty of workers in the sector to relocate in a formal way in other activities.

O objetivo deste trabalho foi avaliar a distribuição espacial de adultos e ninfas da cigarrinha-das-raízes da cana-de-açúcar, Mahanarva fimbriolata (Stål., 1854) (Hemiptera: Cercopidae), a eficiência do sistema de amostragem atualmente empregado em escala comercial, a possibilidade de estimar a população de ninfas por meio da contagem de espumas e, a partir desses resultados, estabelecer um plano de amostragem confiável, prático e de baixo custo para utilização em programas de manejo integrado desta praga. A determinação da distribuição espacial foi feita em Ourinhos e Guariba-SP, demarcando-se três parcelas de 1,1 ha, em talhão colhido mecanicamente sem a queima da palha e com histórico de ataque da cigarrinha-dasraízes. As avaliações foram feitas em três épocas diferentes, contando-se o número de adultos e ninfas na base das touceiras, em 50% da área da parcela. Os adultos e ninfas de M. fimbriolata distribuem-se de forma agregada ou contagiosa na cultura da cana-de-açúcar e este padrão de distribuição não se altera ao longo das gerações, nem é influenciado pelo nível de infestação ou variedade cultivada. Utilizando-se os dados obtidos nestes experimentos calculou-se, para cada local e época de amostragem, o índice de dispersão k e o número de amostras necessárias para estimar a população de ninfas, considerando-se diferentes níveis de precisão, e realizaram-se simulações para diferentes tamanhos de amostra e esquemas de caminhamento. O plano de amostragem mais adequado para avaliação da população da cigarrinha-das-raízes em cana-de-açúcar foi determinado por meio do intervalo de confiança da média (P ≤ 0,05) para a Variação Relativa (VR) e Precisão Relativa (PR). Os melhores resultados foram obtidos com 18 amostras de 1 metro linear por hectare, distribuídas na área de forma sistemática. Para a avaliação do método de amostragem comercial, instalaram-se dois experimentos em Ourinhos, demarcando-se duas parcelas de 1,1 ha, nas mesmas condições anteriores. Quinzenalmente, quantificou-se o número de formas biológicas em 300 pontos de 1m linear na parcela (amostragem experimental) e no restante da área do talhão (amostragem comercial), em 4 pontos de dois sulcos de 2m lineares/ha. Comparando-se os dados por meio de uma análise de regressão linear verificou-se que o método de amostragem comercial apresentou boa precisão na estimativa da população de ninfas, porém foi pouco preciso para adultos. Sua acurácia foi baixa para ninfas e adultos, subestimando as populações reais. A relação entre as contagens de espumas e ninfas nas amostragens comercial e experimental foi avaliada por meio de uma análise de regressão linear, observando-se alta correlação entre estes parâmetros, com coeficientes de determinação superiores a 0,96. Os resultados obtidos indicam que, independentemente da época de avaliação e do nível de infestação, é possível estimar a população de ninfas da cigarrinha-dasraízes em cana-de-açúcar por meio da contagem de espumas, com elevado grau de confiabilidade. / The objective of this research was to evaluate the spatial distribution of adults and nymphs of the sugarcane root froghopper, Mahanarva fimbriolata (Stal, 1854) (Hemiptera: Cercopidae), to evaluate the efficiency of the sampling system presently used to monitor the populations in commercial fields, and to estimate nymph populations by counting foam spots. The results obtained in this work were used to establish a low cost and reliable sampling method in order to improve the integrated pest management program for the sugarcane root froghopper. The determination of the spatial distribution was conducted at Ourinhos and Guariba cities, São Paulo State, in three plots of 1.1 ha that had been mechanically harvested without burning and with a history of infestation with sugarcane root froghopper. The evaluations were made in three different periods, counting the number of both adults and nymphs at the base of the stools in 50% of the plot. The adults and the nymphs of M. fimbriolata were distributed in aggregated or contagious form and this pattern did not change during subsequent generations nor was influenced by either the level of infestation or cultivated variety. The data obtained in these experiments was used to estimate, for each site and sampling period, the dispersion index k and the number of samples needed to estimate nymph populations, considering different levels of precision. The data was also used to simulate results with different sample sizes and sampling patterns. The most adequate sampling plan to evaluate sugarcane root froghopper populations was determined using the confidence interval of the mean at P ≤ 0.05 for the Relative Variation (RV) and Relative Precision (RP). The best results were obtained with 18 samples of 1 linear meter per hectare, distributed in the area in a systematic manner. For the evaluation of the commercial sampling method, two experiments were established at Ourinhos, using two 1.1 hectare plots. The number of biological forms in 300 spots of 1 linear meter in the plot (experimental sampling) were checked bi-weekly. Similarly, in the rest of the area, biological forms were counted in 4 spots of 2 linear meters per hectare (commercial sampling). Linear regression analysis presented that the commercial sampling method presented good efficiency for estimating nymphs populations but was not efficient in estimating adult populations. The sampling accuracy was low for both nymphs and adults, underestimating the true populations. The linear correlation between foam counts and nymph in both commercial and experimental sampling was high, with determination coefficient greater than 96%. The results indicate that, independent of the period and level of infestation, it is possible to estimate the population of sugarcane root froghopper nymphs by counting foam spots.

O cultivo da cana-de-açúcar depara-se com a falta de tecnologias alternativas inovadoras para impulsionar sua produtividade diante dos crescentes custos de mão de obra e insumos, tornando-se essencial aumentar a produtividade da cana de forma sustentável. A cana-de-açúcar é comercialmente plantada, utilizando-se cortes de toletes ou gemas. Este método de cultivo está se tornando gradualmente antieconômico, devido ao elevado custo das \"áreas de viveiros\" usadas para a renovação de canaviais, que demandam mais de 20 por cento do custo total de produção para renovação/novos plantios. Dessa forma, necessita-se de métodos alternativos de plantio, que impulsionem a produtividade da cana-de-açúcar sobre princípios de um planejamento adequado; entre outras práticas, devem estar inclusas a formação de viveiros sadios, com otimização de áreas destinadas à multiplicação de mudas e também a escolha das melhores opções entre os materiais genéticos para a formação do canavial. Este trabalho baseia-se na hipótese de que, para viveiros de cana-de-açúcar, exista uma combinação mais adequada entre a lâmina de irrigação/intensidade do déficit hídrico e a posição da gema ao longo do colmo; desta forma, aumenta-se a produtividade de gemas de cana-de-açúcar, que serão utilizadas no plantio do sistema de mudas-pré-brotadas (MPB). O objetivo deste trabalho foi avaliar, no que se refere ao viveiro de mudas, o efeito de quatro lâminas de irrigação, quatro intensidades de déficit hídrico na fase de maturação, quatro posições ao longo do colmo para oito variedades de cana-de-açúcar irrigadas por gotejamento, assim como também a produtividade por área e os custos de produção de gemas viáveis de cana-de-açúcar. O experimento foi conduzido no município de Piracicaba - SP, no Departamento de Engenharia de Biossistemas da Escola Superior de Agricultura \"Luiz de Queiroz\" (ESALQ/USP), em ambiente protegido (estufa). O delineamento experimental adotado foi em blocos inteiramente aleatorizados, com três blocos completos. Os tratamentos foram distribuídos em esquema fatorial (4x4x4x8), totalizando-se assim 511 tratamentos e 1536 parcelas experimentais. Os tratamentos testados foram: lâmina de irrigação ao longo do ciclo, com quatro níveis (Lâmina); intensidade do déficit hídrico na fase final do ciclo para maturação da cana-de-açúcar, com quatro estratégias de restrição hídrica (Maturação); posição da gema ao longo do comprimento do colmo, com quatro posições (Posição); e variedade comercial de cana-de-açúcar, com oito variedades (Variedade). Considerando-se que o presente estudo foi desenvolvido através de irrigação por gotejamento de alta frequência sob irrigação plena e irrigação com déficit, pode-se concluir que: a) a lâmina de irrigação que repõe o total de água requerido com alta frequência (L100) promove um aumento médio de 42% no total de gemas viáveis produzidas por hectare, comparado com o fornecimento de metade da lâmina de irrigação requerida (L50); b) as gemas localizadas no segundo quarto do dossel da touceira tem maior capacidade de pegamento, bem como as próximas do ápice; c) a adoção de déficit hídrico na fase pré-colheita (estratégias de maturação) em condições de irrigação plena (L100) podem reduzir em média 11% o número de gemas viáveis por hectare; d) a produtividade da água para gemas de cana-de-açúcar (2,88 à 3,17 litros gema-1) não tem relação com a lâmina de irrigação ou a estratégia de maturação adotada, sendo influenciada somente pelo material genético utilizado (variedade); e) as estratégias de restrição do volume de água aplicado (L50, L75 e L125) oneram em até 51% os custos de produção para cada gema viável produzida, comparado à irrigação plena (L100). / Sugarcane crop is facing a difficult road ahead due the rising input and labor costs and the lack of innovative alternative technologies to boost productivity. Thus, it is essential not only increase the productivity of sugarcane, but also keep it in a sustainable way, had conserving limited resources throughout time. To accomplish this, there is a strong necessity to use alternative methods of production to boost sugarcane productivity on the principles of \'\'more with less\'\'. More than ever, the answer refers to proper planning, which includes among other practices, the formation of healthy nursery, with definable areas intended to multiplication of seedlings and the choice of the best options among the available materials for the formation of cane field. Sugarcane is cultivated using cuts of stalks or bud chips and this cultivation method is gradually becoming uneconomical due the cost of \"nurseries areas\" used for renew old areas, requiring more than 20 percent of the total production cost for renovation/new plantings. This work has the hypothesis that for sugarcane, there is a better combination of water depth / intensity of water stress and bud chip position along the stem, in order to maximize the fixation / development of buds. The objective is evaluate the effect of four irrigation levels, four water stress intensities in the maturation phase, four positions along the stem, for eight varieties of sugarcane submitted to drip irrigation, analyzing the related variables quality seedlings (productivity and cost of viable buds of sugarcane). The experiment was conducted in Piracicaba - SP, in the research area of the Department of Biosystems Engineering of the College of Agriculture \"Luiz de Queiroz\" (ESALQ / USP), in a protected environment (greenhouse). The experimental design was completely randomized blocks, with 3 complete blocks. The treatments were arranged in a factorial design (4x4x4x8), totaling 511 treatments and 1536 experimental plots. The treatments were: water depth during the cycle with 4 levels (Water depths); commercial variety of cane sugar, with 8 varieties (Variety), intensity of water deficit in the final phase of the maturation of sugarcane, 4 water restriction strategies (maturation); and bud chip position along the stem length, 4 position (position). Considering the conditions in which this study was developed: drip irrigation high frequency under full irrigation and irrigation deficit, it can be concluded that: a) The water depth that returned the total water required in high frequency (L100) promotes an average of 42% increase in total viable bud chips produced per hectare, compared with when it was supplied half of the required water depth (L50); b) Bud chips located in the second part of the canopy has a higher fixation capacity, as well as the buds located at the top; c) The adoption of water deficit in the pre-harvest phase (maturity strategies) in full irrigation conditions (L100) can reduce an average of 11% the number of viable buds per hectare; d) The water productivity of sugarcane bud chip (2,88 à 3,17 litros gema-1) has no relation to the water depth or adopted maturation strategy, being influenced by the used genetic material (variety); e) The restriction water strategies applied (L50, L75 and L125) can increase up to 51% of the costs for each viable bud produced compared to full irrigation (L100).

Although silicon (Si) has not yet been recognized as an essential nutrient element, its application to sugarcane (Saccharum officinarum L.) has proved to be beneficial. Since optimum crop production depends on the maintenance of adequate plant nutrients in the soil, there is a need in the South African sugar industry for a reliable index for assessing the requirement for supplemental silicon (Si) in soils, particularly in reducing the risk of Eldana saccharina stalk borer infestation in cane. The objective of this study was to assess Si availability in soils, to select a suitable Si extraction method and a critical value for determining when a response is likely. For this purpose, five acid soils (representing. some of the most important agricultural soil groups used for sugarcane production in the sugar belt) were used in October 2004, in the lAKE WILSON glasshouse of the South African Sugarcane Research Institute (SASRI) based at Mount Edgecombe. Except for the Arcadia form soil with an initial Si content of 1.2 mmol kg- I as estimated using the O.OlM H2S04 + (NH4)zS04) extractant, soils representing the other five soil forms namely Cartref, Glenrosa, Longlands and Nomanci; exhibited a sub-optimal Si content of not more than 4.0 mmol kg-I. Sorghum was used as a plant crop and sugarcane as a ratoon crop because of their Si accumulator status. Three different Si sources: calmasil, slagment and wollastonite; with respectively 9.85, 15.20, and 5.25% Si content were applied at increasing rates of 0, 3 and 6 tons ha- 1 as Si fertilizers. Silicon (Si) was extracted from untreated and treated soils by utilizing six different extractants, (1) O.OlM H2S04 + (NH4)2S04; (2) Distilled water; (3) 0.025M H2S04; (4) 0.5M CH3COOH; (5) 0.5M CH3COONH4pH 4.8; and (6) O.OlM CaCh.2H20. The amount of soil Si extracted followed the order: 0.025M H2S04 > 0.5M CH3COOH > O.OlM H2S04 + (NH4)2S04 > O.OlM CaCh.2H20 > 0.5M CH3COON~ pH 4.8 > distilled water. Soil Si extracted by 0.025M H2S04 was significantly correlated with soil exchangeable cations,. CEC, clay content, cane biomass yield, cane Si uptake and increasing rates of applied Si. Averaged over all soil forms investigated, the increases in dry biomass yield and Si uptake ranged. from 18% to 154% for sorghum; and from 23% to 85% for cane respectively. Even though the highest increases (%) in cane biomass yield and Si uptake were obtained on a Nomanci form soil with initial poor fertility status, the highest means were obtained on an Arcadia form soil with the highest Si initial content. There was no difference between different Si sources in their ability to influence cane biomass yield and Si uptake, and therefore the supply to the soils. Even though the lower and higher Si source rates were not different from each other, they increased cane yield and Si uptake, indicating that Si was undoubtedly beneficial for sugarcane. The Si critical levels for different soils as estimated by 0.025M H2S04 were 6.0 mmol kg-1 (168 mg kg-I) for Arcadia; 2.6 mmol kg-I (64 mg kg-I) for Cartrel; 2.5 mmol kg-I (64 mg kg-I) for Glenrosa; 1.6 mmol kg-I (45 mg kg-I) for Longlands; and 2.4 mmol kg-I (67 mg kg-i) for Nomanci form soils. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2007.

The productivity of small-scale sugarcane contractors affects not only their own profitability and sustainability, but that of other stakeholders as well, such as the small-scale sugarcane farmers they contract to and the sugar mills these farmers supply in the form of improved services to growers and a steady flow of sugarcane to mills. This study firstly illustrates the organisational structures of the sugar industry. It then aims to identify constraints that inhibit the performance (such as timely haulage operations and cost effectiveness) of small-scale sugarcane contractors in the small-scale sugar industry of KwaZulu-Natal (KZN). To obtain this information, interviews were conducted with 124 randomly selected contractors from 11 mill group areas in KZN between September 2002 and July 2003. Case studies (concerning institutional issues such as organisational structures) of contractors, sub-committee members, and development officers were also conducted in eight mill group areas of KZN between September 2002 and February 2004. Sample statistics and case study results show that contractors face institutional constraints (work allocation limitations, lack of performance incentives and high transaction costs, such as negotiation costs, the risk of losing work and contract default risk), cash flow problems, poor physical infrastructure and a lack of labour. It is concluded that the promotion of a more competitive small-scale sugarcane contractor sector will alleviate many of the problems (such as work allocation limitations) faced by small-scale contractors, while providing incentives for the provision of higher quality and cheaper services to small-scale sugarcane growers. The study also examines the attributes of small-scale sugarcane contractors that affect their quality of service as perceived by small-scale sugarcane growers (SSGs) within current institutions. Information is drawn from the same sample survey, although ten observations from the Umfolozi area are excluded because they were not part of the sample drawn from population lists. Further interviews were conducted in the same time period with SSGs for information on contractor service quality (transport and general service timeliness, meeting of daily ratable delivery requirements, low downtimes, good staff management, and minimal disagreements on service terms). Results show that factors affecting a contractor's perceived service quality include gender, training, the quality of information used (industry focused information sources such as the South African Sugar Association Experiment Station (SASEX) and the Ingede magazine, or general sources such as the radio), and sugarcane tonnage transported (size of business). Being a male contractor and having a larger business positively influence service rating as perceived by SSGs. The importance of the quality of information used and increased training levels highlights the need for the continual provision of relevant information and training for sugarcane contractors by extension services (government, SASEX and milling companies). The study also identifies the need for further research on the issue of contractor machinery costs. In a competitive sector contractors would need to have adequate information on own costs in order to compare these with contract rates in the market. Further guidance by extension staff and other industry advisors (e.g. development officers) in the accessing of adequate finance may also be necessary. Government has a role in strategising the creation of land markets to promote efficient use of resources (land), while providing improved rural infrastructure (mainly district roads). Government also needs to ensure unbiased tribal court rulings, review the impacts of minimum wage legislation on contractors sourcing labour, and provide protection for those competing for work. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2004.

Five potential resistance-inducing chemicals were applied to two sugarcane varieties (N12 and N27) in a pot trial with the aim of inducing resistance to nematodes in naturally-infested soil. BION® (acibenzolar-S-methyl), methyl jasmonate, cis-jasmone and 2,6-dichloroisonicotinic acid (INA) were applied as a foliar spray and suSCon® maxi (imidacloprid) applied to the soil. All chemicals were tested at two rates and plants were sprayed one week prior to being harvested at 7, 9 and 11 weeks of age. Meloidogyne and Pratylenchus infestation of sett and shoot roots was determined at each harvest. The activity of four pathogenesis-related proteins was examined at 7, 9 and 11 weeks using separate assays, these enzymes where chitinase, β-1,3-glucanase, peroxidase and polyphenol oxidase. Methyl jasmonate treatment produced significant increases in β-1,3-glucanase, chitinase and peroxidase activity. All other elicitor treatments showed little difference in enzyme activity from the Control. The effect of each treatment on plant growth was examined by recording the dried root and shoot biomass of each plant. No significant differences were seen (p<0.05; Holm-Sidak test). However, root and shoot dried biomass was highest in the N12 variety treated by suSCon® maxi. The infection of sugarcane with Ustilago scitaminea (sugarcane smut) is commonly identified visually by the presence of a smut whip. Identification of sugarcane smut infection can be determined prior to whip development by staining tissue sections with lactophenol cotton blue and examining plant tissues microscopically. This allows for a rapid determination of smut infection which can aid breeding programs. Smut infection is achieved in vitro by soaking sugarcane setts in smut spores collected from infected whips. Four methods of inoculation were examined. The method that most consistently caused infection involved allowing setts to germinate for 24 hours, before puncturing a bud with a toothpick, followed by submerging the sett in 1x10⁸ smut spores per mℓ. An elicitor of systemic acquired resistance called BION®, and an insecticide with resistance-inducing properties called Gaucho® (imidacloprid) were used as a sett soak treatments to induce resistance to sugarcane smut. The effect of each treatment at three concentrations on plant germination and growth was examined in the NCo376 variety. Smut spore germination on agar was examined in the presence of both treatments at three concentrations. Sugarcane setts were treated with a concentration that did not significantly reduce the germination of smut spores or sugarcane setts. Plants were infected with smut post treatment and allowed to grow for approximately one month until plants were between 8 and 10 cm in height. Smut infection was assessed by cutting longitudinal sections through the base of the shoot and staining each section with cotton blue lactophenol. Treatment with BION® and Gaucho® did not reduce smut infection. / M.Sc.Agric. University of KwaZulu-Natal, Pietermaritzburg 2013.

Weed control is a major cost for growers in the sugarcane industry, especially for monocotyledonous species such as Cynodon and Rottboellia spp. The introduction of imazapyr-tolerant sugarcane would be advantageous as this herbicide has shown to be effective against the above-mentioned weeds but it also kills sugarcane. In a previous study in our laboratory, several sugarcane putative-mutant lines of variety N12 were generated by in vitro exposure of embryogenic callus to 16 mM ethyl methanesulfonate (EMS), followed by selection on imazapyr-containing medium. Tolerance to a low dose of imazapyr was confirmed in seven of those lines when the herbicide was applied (182 g a.i. ha-1) to 3 month-old plants in pots. The aim of the present study was to identify which of the seven herbicide mutant lines had agronomic characteristics at least equivalent to un-mutated N12. The objectives were to: 1) confirm tolerance to increased rate (312 and 625 g a.i. ha-1) of imazapyr in field plants; 2) measure the agronomic characteristics of these lines; 3) determine the effect of residual soil herbicide activity on germination of sugarcane setts. The seven mutant lines (Mut1-Mut7) and un-mutated N12 were clonally propagated in vitro by shoot multiplication followed by rooting and planted in three plots (untreated, sprayed with 312 or 625 g a.i. ha-1 imazapyr), in the field, in a randomized complete block design. In the untreated control plot there were no significant differences between the control and the mutant plants for agronomic traits (tiller number/plot, stalk height and stalk diameter) or estimated yield (kg/plot) after 10 months, indicating that the mutation process had no effect on general plant phenotype. In the sprayed (312 and 625 g a.i. ha-1) plots, Mut1, Mut4, Mut5, Mut6 and Mut7 plants showed tolerance to imazapyr as the leaves remained green compared with Mut2, Mut3 and N12 control plants, which displayed chlorotic leaves and eventually died in the plot sprayed with 625 g a.i. ha-1. Post-herbicide application, the yields of Mut5, Mut6 and Mut7 (52.33, 43.43 and 41.43 kg/plot, respectively) from the 312 g a.i. ha-1 plot were not significantly different from that of N12 control (53. 61 kg/plot) in the untreated plot. However, in the 312 g a.i. ha-1 plot, the yield and agronomic trait measurements of the untreated N12 control were significantly higher than those of the herbicide-susceptible plants Mut2 and Mut3. Similarly, in the 625 g a.i. ha-1 plot, the recorded yields for Mut4, Mut6 and Mut7 were 41.60, 43.44 and 36.30 kg/plot, respectively, indicating that their imazapyr tolerance and yield characteristics were comparable to the untreated N12 control. Imazapyr is conventionally applied to a fallow field 3-4 months prior to planting sugarcane as there is residual herbicide activity in the soil that suppresses sugarcane germination and growth. Therefore, in order to establish if the herbicide-tolerant mutants could germinate in iii an imazapyr-treated field, 3-budded setts of the mutant lines (Mut1-Mut7) and N12 control were planted in two plots, one unsprayed and one sprayed with 1254 g a.i. ha-1 imazapyr, 2 weeks previously. Germination was calculated after 3 weeks as the number of germinated setts in each plot/no. germinated setts in unsprayed plot x100. In the sprayed plot, the setts from Mut1, Mut4 and Mut6 displayed the highest germination percentages (60, 71 and 74%, respectively) compared with Mut2 (24%), Mut3 (46%), Mut5 (34%), Mut7 (40%) and the N12 control (12%). The in vitro acetolactate synthase (ALS) enzyme activity of 10 month-old plants from the untreated plot was assessed in the presence of 0-30 μM imazapyr to determine the herbicide concentration that inhibited ALS activity by 50% (IC50). The IC50 values for the mutated lines were between 3 and 30 μM, i.e. 1.5-8.8 times more tolerant to imazapyr than the N12 control plants, with Mut6 displaying the highest IC50 value (30 μM). On the basis of the results, it was concluded that Mut1, Mut6 and Mut7 lines were more tolerant to imazapyr than N12 and the other tested lines. Future work includes phenotypically assessing these lines for traits including sucrose content, fibre content, actual yield (tons cane ha-1) and altered pest and disease resistance. Once isolated and sequenced, the ALS gene conferring imazapyr tolerance can be used in genetic bombardment in the genetic modification approach as the gene of interest or as a selectable marker. In addition, the imazapyr-tolerant line can be used for commercial purposes in the field and as the parent plant in the breeding programme. / Thesis (M.Sc.Agric.)-University of KwaZulu-Natal, Durban, 2013.

Thesis (MSc (Plant Biotechnology))--University of Stellenbosch, 2007. / Sugarcane is cultivated because of the high levels of sucrose it stores in its internodes. Starch metabolism has been a neglected aspect of sugarcane research despite the problems caused by it during sugarcane processing. Currently there is no information available on the starch content in different South African commercial sugarcane varieties. This project had two main aims of which the first was to determine the starch content in the internodal tissues of six commercial sugarcane varieties. The activities of ADP-Glucose Pyrophosphorylase (AGPase) and β- amylase were also determined. The second aim of the project was to manipulate starch metabolism in sugarcane using transgenesis. To achieve this, transformation vectors for the down-regulation of AGPase activity and over-expression of β-amylase activity were designed. These vectors were then used to transform sugarcane calli and the results were analysed in suspension cultures. Starch levels in sugarcane internodal tissue increased more than 4 times from young to mature internodes. There were also large differences between varieties. When mature tissues of different varieties were compared, their starch concentration varied between 0.18 and 0.51 mg g-1 FW, with the majority of the varieties having a starch concentration between 0.26 and 0.32 mg g-1 FW. NCo376’s starch concentration was much lower than the rest at 0.18 mg g-1 FW and N19’s was much higher at 0.51 mg. g-1 FW. There was also a very strong correlation between starch and sucrose concentration (R2 = 0.53, p ≤ 0.01) which could be due to the fact that these metabolites are synthesized from the same hexose-phosphate pool. No correlation was evident between starch concentration and AGPase activity. This was true for correlations based on either tissue maturity or variety. β-amylase activity expressed on a protein basis was almost 5 times higher in the young internodes compared to mature internodes, suggesting that carbon might be cycled through starch in these internodes. AGPase activity in the transgenic suspension cultures was reduced by between 0.14 and 0.54 of the activity of the wild type control. This reduction led to a reduction in starch concentration of between 0.38 and 0.47 times that of the wild type control. There was a significant correlation between the reduction in AGPase activity and the reduction in starch (R2 = 0.58, p ≤ 0.05). β-amylase activity in the transgenic suspension cultures was increased to 1.5-2 times that of the wild type control. This led to a reduction in starch concentration of between 0.1 and 0.4 times that of the wild type control. Once again the increase in β-amylase activity could be correlated to the reduction in starch concentration of the transgenic suspension cultures (R2 = 0.68, p ≤ 0.01). In both experiments there was no significant effect on sucrose concentration.

Thesis (MSc (Genetics. Plant Biotechnology)) --Stellenbosch University, 2008. / The main aim of the work presented in this thesis was to further our understanding of the role of Pyrrophosphate: fructose 6-phosphate 1-phosphotransferase (PFP) in sugarcane, by specifically investigating its potential contribution to phloem metabolism. PFP activity in sugarcane internodal tissue is inversely correlated to sucrose content across varieties that differ in their sucrose accumulation abilities. This apparent correlation is in contrast to previous studies that suggest PFP plays an insignificant role in metabolism. In the first part of this study an immunological characterisation of the two subunits of sugarcane PFP was conducted to establish whether it differ significantly from other plant species in terms of size and distribution. Both the alpha and beta subunit appears to be approximately sixty kilo Daltons in size and uniform in their relative distribution to each other in the various plant organs of sugarcane. Although the observed alpha subunit size is less than that predicted this could be explained at the hand of post translational modification, in essence the sugarcane PFP subunits appear similar than that described for other plants especially that of tobacco which was employed as a model system later on in this study. The only direct way to investigate PFP’s contribution to phloem metabolism is to alter its activity by recombinant DNA technologies. Therefore, in the second part of the study transformation systems were designed for both the constitutive and phloem specific downand up-regulation of PFP activity. For the down-regulation of activity a post transcriptional gene silencing system, i.e. a complementary strand intron hairpin RNA (ihpRNA) silencing system, was employed. A partial sequence of the PFP-beta subunit was isolated and used in vector construction. For the over-expression the Giardia lamblia PFP gene was used. The model plant tobacco was employed to investigate PFP’s effect on phloem metabolism and transport of assimilate. Transgene insertion was accomplished by means of Agobacterium mediated transformation and tissue specific manipulation of PFP activity was confirmed by in situ activity staining.