Kenaf (Hibiscus cannabinus L.) was introduced in 2005 as a fibre crop on a commercial scale in the KwaZulu-Natal Province of South Africa. No herbicides have yet been registered for use in this crop. The purpose of this study was to determine the tolerance of kenaf to a total of five pre-emergence and four post-emergence herbicides under semi- and fully controlled conditions. The herbicides were chosen based on their potential safety for use in Hibiscus spp. as well as on the weed spectra they are registered for in other crops. Several additional factors were also taken into consideration, such as: temperature, soil depth and timing of herbicide application. Four pot trials were conducted to determine the separate and combined effects of herbicide, temperature, planting depth and application timing. During the first trial the effects of five pre-emergence herbicides and four post-emergence herbicides were researched. The pre-emergence herbicides were: S-dimethenamid, imazethapyr, fluometuron/prometryn, pendimethalin, S- metolachlor and the post-emergence herbicides were: bentazone, 2,4-DB, monosodium methanearsonate and pyrithiobac sodium. The trials were conducted under either semi-controlled conditions in a glasshouse or in growth cabinets under fully controlled conditions at the Hatfield Experimental Farm of the University of Pretoria. All experiments were conducted with a Hutton soil with 22% clay. Each trial lasted about 40 days to allow for maximum phytotoxicity damage manifestation on the kenaf seedlings. Measurements that were taken included plant height, herbicide damage, weed control efficiency, fresh plant weight, dried plant weight, and dried root weight. The data were subjected to analysis of variance (ANOVA) to determine the statistical likelihood of damage to plants from the herbicides. In Trial 2, 3 and 4 the interaction effects of herbicide and plant depth, herbicide and temperature, and herbicide and application timing were researched respectively. Neither planting depth nor application timing affected the kenaf seedlings negatively, but low temperature in combination with the application of herbicides during germination of seed and seedling emergence had serious deleterious effects on the young kenaf seedlings. Based on the findings the majority of the herbicides can be included in further field trials on Hibiscus cannabinus L. with the exception of S-dimethenamid and fluometuron/prometryn which caused substantial injury to the kenaf seedlings. Copyright / Dissertation (MInstAgrar)--University of Pretoria, 2011. / Plant Production and Soil Science / unrestricted

La toxicité des émissions de formaldéhyde rejetées par les panneaux de particules à base de résines contenant du formaldéhyde motive la recherche de liants alternatifs notamment d’origine naturelle. Ce travail porte sur l’élaboration par thermopressage et la caractérisation physico-mécanique de panneaux de particules sans ou à faibles rejets de formaldéhyde à partir des tiges de kénaf (Hibiscus cannabinus) et de la colle d’os ou de liants végétaux riches en tannins ou en mucilage de plantes tropicales. L’utilisation de ces bioadhésifs a permis d’obtenir des panneaux de bonne résistance en flexion (370 = MOE = 3100 MPa ; 2,01 = MOR = 23 MPa). Un procédé peut être envisagé pour une production de ces panneaux utilisables comme matériaux de construction écologiques / The proven toxicity of lignocellulosic composites based on urea-formaldehyde, phenol-formaldehyde type resins by their formaldehyde emissions cause environmental health problems. A study has been carried out to enhance the development of particleboards of low density with few formaldehyde emissions manufactured with Hibiscus cannabinus core reinforcements and matrix of bone adhesive or tannin material from pod of Parkia biglobosa, stem barks of Pithecellobium dulce and foliar sheath of Sorghum caudatum or mucilaginous material from calyx of Bombax costatum and stem barks of Grewia venusta. Vegetable materials were employed in rough powders or extracts forms, or in mixture with the bone adhesive. The results obtained reveal that bone adhesive was as valuable as the urea formaldehyde resin for manufacturing particleboard with good mechanical properties (MOE: 541 MPa, MOR: 5.23, IB: 0.58 MPa). Tannin and mucilaginous rough materials gave particleboards with bending modulus of elasticity (MOE) ranging from 370 to 400 MPa, bending modulus of rupture (MOR) varying from 2.01 to 3.17 MPa and internal bond (IB) going from 0.06 to 0.28 MPa. Those plant extracts leaded to particleboards with variable mechanical properties (MOE: 484 –1100 MPa, MOR: 2.36 – 5.66 MPa and IB: 0.11 – 0.46 MPa) depending of the nature of the adhesive. Tannin based adhesive gave particleboards more valuable than mucilaginous ones. The association of the bone adhesive with the rough or the extracts of the plants material improved the mechanical characteristics of the panels

Submitted by Mario BC (mario@bc.ufrpe.br) on 2018-03-14T13:55:45Z No. of bitstreams: 1 Kaliny Veiga Pessoa da Silva.pdf: 1645641 bytes, checksum: 7d934fe1a156047987054c35f1981b65 (MD5) / Made available in DSpace on 2018-03-14T13:55:45Z (GMT). No. of bitstreams: 1 Kaliny Veiga Pessoa da Silva.pdf: 1645641 bytes, checksum: 7d934fe1a156047987054c35f1981b65 (MD5) Previous issue date: 2016-08-22 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Cotton stands out as a high value textile plant in the world market due to the quality of its fibers and the commercial derivatives that the plant produces. Ramulose is a disease that causes great damage to this crop, caused by the fungus Colletotrichum gossypii South var. cephalosporioides Costa, mainly affects young leaves, the most common symptoms being the darkening and necrosis of leaves and branches, which may compromise the whole development of the plant. Extracts and vegetable oils have been studied as an alternative to control pests and diseases such as ramulose in crops. These have as main constituents the secondary compounds, chemicals known as phytochemicals, terpenoids, alkaloids and glycosides. Among these the geraniol, monoterpene that stands out for its fungicidal property. Kenaf (Hibiscus cannabinus) belongs to the family Malvaceae and is rich in compounds known as polyphenols, alkaloids, tannins and essential oils, also being a promising source of fungicidal oil. This work aimed to analyze the effect of oils and extracts on the development of the fungus C. gossypii, which causes ramulose, by means of two researches: In the first one, we sought to prospect Geraniol synthase, the precursor enzyme of geraniol, in aromatic species, for means of molecular analyzes via PCR and qPCR, besides phytopathological tests, in order to evaluate the geraniol expression and the effectiveness of its extracts and vegetable oils in the prevention and control of ramulose; The second study evaluated the effect of Kenaf oil on the development of fungus C. gossypii under laboratory conditions. In order to carry out the first research eleven aromatic species were evaluated, among them M. pulegium, O. basilicum, O. majorana and R. officinalise, which presented satisfactory levels of expression of this enzyme in the molecular assays, being selected for bioassays in vivo against C. gossypii. O. basilicum, M. pulegium and O. majorana oils, at 2000 ppm concentration, were tested in vivo and their preventive and curative actions compared to commercial fungicide. There was effective control of the oils O. basilicum and M. pulegium under ambient conditions, and M. Polegium was distinguished with D.S.I. around 30%, lower value than that presented by the commercial fungicide (40%). These results indicate that the use of aromatic species can be an effective alternative for the treatment of ramulose, with the advantages of being a low cost method and not presenting risks of environmental contamination. In addition, the genetic characterization of aromatic species is an important source of information to expand the use of natural resources, allowing new materials that hold genes of interest to be found and serve as environmental conservation strategies. In the second study, phytopathological tests were performed on isolate 287 of C. gossypii on the effect of Kenaf oil at concentrations of 25, 50 and 75 μl / 1 ml. It was verified by regression analysis that there was no reduction in the mycelial growth of C. gossypii in the oil concentrations adopted in this work. The data presented by fungus growth, fungistatic effect and spore production did not reveal a statistical difference between the treatment with oil and control. Based on the composition of kenaf oil, rich in fungicidal ingredients, even this oil lacking control over C. gossypii in the present study, it is believed that in higher concentrations this oil may exert an effect on this pathogen. / O algodoeiro destaca-se como uma planta têxtil de alto valor no mercado mundial devido à qualidade de suas fibras e aos derivados comerciais que a planta produz. A ramulose é uma doença que causa grandes danos a esta cultura, causada pelo fungo Colletotrichum gossypii South var. cephalosporioides Costa, afeta principalmente folhas jovens, sendo os sintomas mais comuns o escurecimento e necrose das folhas e ramos, podendo comprometer todo o desenvolvimento da planta. Extratos e óleos vegetais vêm sendo estudados como alternativa para controle de pragas e doenças como a ramulose em lavouras. Estes têm como principais constituintes os compostos secundários, substâncias químicas conhecidas como fitoquímicos, terpenóides, alcalóides e glicosídeos. Dentre estes o geraniol, monoterpeno que destaca-se por sua propriedade fungicida. Já o Kenaf (Hibiscus cannabinus) pertence à família Malvaceae e é rica em compostos conhecidos como polifenóis, alcalóides, taninos e óleos essenciais, também sendo uma promissora fonte de óleo fungicida. Este trabalho buscou analisar o efeito de óleos e extratos sobre o desenvolvimento do fungo C. gossypii, causador da ramulose, por meio de duas pesquisas: Na primeira, buscou-se prospectar a Geraniol synthase, enzima precursora do geraniol, em espécies aromáticas, por meio de análises moleculares via PCR e qPCR, além de testes fitopatológicos, a fim de avaliar a expressão do geraniol e a eficácia de seus extratos e óleos vegetais na prevenção e no controle da ramulose; Na segunda pesquisa avaliou-se o efeito do óleo de Kenaf sobre o desenvolvimento do fungo C. gossypii em condições de laboratório. Para realização da primeira pesquisa onze espécies aromáticas foram avaliadas, entre elas M. pulegium, O. basilicum, O. majorana e R. officinalise, as quais apresentaram níveis satisfatório de expressão desta enzima nos ensaios moleculares, sendo selecionadas para bioensaios em in vivo contra C. gossypii. Os óleos de O. basilicum, M. pulegium e O. majorana, na concentração de 2000 ppm, foram testados in vivo e suas ações preventivas e curativas comparadas com fungicida comercial. Houve controle efetivo dos óleos O. basilicum e M. pulegium em condições ambiente, sendo que M. Polegium destacou-se com D.S.I. em torno de 30%, valor menor do que o apresentado pelo fungicida comercial (40%). Esses resultados denotam que o uso de espécies aromáticas pode se constituir numa alternativa eficaz para o tratamento da ramulose, com as vantagens de ser um método de baixo custo e de não fornecer riscos de contaminação ambiental. Além disso, a caracterização genética de espécies aromáticas é uma importante fonte de informações para ampliar a utilização dos recursos naturais possibilitando que novos materiais detentores de genes de interesse sejam encontrados e sirvam como estratégias de conservação ambiental. Na segunda pesquisa, testes fitopatológicos foram realizados no isolado 287, de C. gossypii, sobre o efeito do óleo de Kenaf em concentrações de 25, 50 e 75 μl/1ml. Verificou-se por análise de regressão que não houve redução no crescimento micelial de C. gossypii nas concentrações de óleo adotadas neste trabalho. Os dados apresentados pelo crescimento de fungos, efeito fungistático e produção de esporos não revelaram diferença estatística entre o tratamento com óleo e controle. Com base na composição do óleo de kenaf, rica em ingredientes fungicida, mesmo este óleo não apresentando controle sobre C. gossypii no presente estudo, acredita-se que em concentrações mais elevadas este óleo possa exercer efeito sobre este patógeno.