Imidazolinones represent a new class of herbicides with low mammalian toxicity that can be used at low application rates, either pre- or post-emergence for the control of a wide range of weeds in broadleaf and cereal crops, and non-crop situations. All imidazolinone herbicides are chiral, containing two enantiomers that derive from the chiral centre of the imidazolinone ring. The inhibitory activity of the R(+) enantiomer is nearly eight times greater than that of the S(-) enantiomer. The use of imidazolinone herbicides has increased in recent years in Australia owing to increased popularity of pulses and the introduction of imidazolinone-tolerant canola and wheat. Concerns have been raised about the potential carry over damage to the subsequent crops grown in rotation with legumes and herbicide tolerant crops. Furthermore, the presence of alkaline soils in some regions of Australia may lead to the repellence of imidazolinone herbicides, which are chiefly present in anionic form at high pH values. Thus leaching and potential contamination of ground water may occurr when these herbicides are applied on alkaline soils in certain agroclimatic zones. There is some information in the literature on the degradation, sorption and leaching behaviour of these herbicides in the environment. However, there is little information about the behaviour of these herbicides in alkaline soils found in some areas of Australia. Until now there has been no investigation of enantioselectivity in the degradation of imidazolinone herbicides in soils. Therefore, this study was undertaken to determine the behaviour of three imidazolinone herbicides in solution and Australian soils including enantioselectivity in the degradation of these herbicides in Australian soils. Analytical method for these herbicides needed to be developed/improved to cater for specific experimental conditions for this study, namely the matrices containing higher levels of organic carbon and to analyse the two enantiomers of these herbicides. The extraction of imazapyr, imazethapyr and imazaquin was investigated using solid-phase extraction (SPE) procedure. The evaluation of different aqueous solutions (0.1 KCl, 0.5 M NaOH, 0.01M NaOH and 0.5M MeOH:NaOH, (80:20)) showed that the recovery of all three herbicides was greater than 70%. However, the highest level of herbicide recovery was obtained with 0.5M NaOH as the extraction solution. Evaluation of different solid phase extraction cartridges showed that PPL cartridge is most appropriate for the isolation and subsequent quantification of these herbicides in water and humic-amended solutions when used at pH 2. When used with soil extracts, SPE cartridges C[subscript]18 + SCX allowed removal of co-extracting substances, resulting in high levels of herbicide recovery and accurate quantification with HPLC. These improved protocols were used in subsequent studies. The abiotic degradation of the imidazolinone herbicides imazapyr, imazethapyr and imazaquin was investigated under controlled laboratory conditions. Hydrolysis, where it occurred, and photodegradation both followed first order kinetics for all herbicides. There was no hydrolysis of any of the herbicides in buffer solutions at pH 3 or pH 7; however, slow hydrolysis occurred at pH 9. Degradation of the herbicides in the light was considerably more rapid than in the dark with half lives for the three herbicides of 1.8, 9.8 and 9.1 days for imazaquin, imazethapyr and imazapyr, respectively. The presence of humic acids in the solution reduced the rate of photodegradation for all three herbicides, with higher concentrations of humic acids generally having greater effect. The enantioselectivity of photodegradation was investigated using imazaquin, with photodegradation occurring at the same rate for both enantiomers. Abiotic degradation of imidazolinone herbicides on the soil surface only occurred in the presence of light. The rate of degradation for all three herbicides on the soil surface was slower than in solution, with half-lives of 15.3, 24.6 and 30.9 days for imazaquin, imazethapyr and imazapyr, respectively. Sterilizing the soil significantly (p < 0.05) decreased the degradation rate of both enantiomers of imidazolinone herbicides, with 81.5 to 89.5% of each enantiomer of the two herbicides remaining unchanged. However, in non-sterilized soils, the degradation of imazapyr and imazethapyr showed enantioselectivity with faster degradation of R(+) enantiomer compared with S(-) enantiomer. There were also some differences in enantioselectivity between different soils, which could be related to variation in microbial populations and enzymes present in different soils. Soil pH had a significant effect on enantioselectivity, which could be due to the effect of this soil property on herbicide sorption and ease of its availability for microbial degradation. This aspect however needs further investigations. Results from studies on soils receiving organic amendment (lupin residue) showed that degradation of the S(-) and R(+) enantiomers of imazethapyr and imazaquin followed firstorder reaction with half-life values of 45.9 to 105 days in non-sterilized soils for S(-) and R(+) enantiomers, respectively. Irrespective of the organic amendment, the degradation rate of the S(-) and R(+) enantiomers of the two herbicides was greater in the Roseworthy (pH 8.2) soil compared with the Clare soil (pH 5.2). Addition of lupin residue as organic amendment (2% w/w) increased degradation rates of both the S(-) and R(+) enantiomers of imazethapyr and imazaquin and significantly (p < 0.05) decreased their half-lives in the Clare soil. However, this amendment produced no significant change in degradation of enantiomers of either of the two herbicides in Roseworthy soil. The enantiomer fraction (EF) values of both herbicides increased over time, which suggested selective degradation of one enantiomer in preference to the other depending on the type of soil and amendment treatment. In the Clare soil, organic amendment increased the EF value at the end of incubation period from 0.61 to 0.76 for imazethapyr and from 0.56 to 0.66 for imazaquin, indicating enantioselective degradation of these herbicides. There was no significant increase in EF values for both herbicides in Roseworthy soil as the result of organic amendment. In conclusion, photodegradation of imidazolinone herbicides was found to have a major impact on the behaviour of these herbicides in aqueous and soil matrices. The degradation of imidazolinone herbicides in the soil was enantioselective, however, the enantioselectivity tended to be compound-specific and was related to soil types. The findings of this study are expected to be useful for the manufacturers to decrease the amount of chemical load in the environment. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1331166 / Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2008

Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, Discipline of Plant and Food Science, 2008. / Includes bibliography (leaves 151-177) Also available in print form.

Thesis (M.S.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on October 26, 2007) Vita. Includes bibliographical references.

Limitations to broadleaf weed management options in chickpea present obstacles for stable production. Even with low weed incidence, chickpea yield can be severely affected, creating need for an integrated weed management system. Due to zero-tillage commonly practiced in Saskatchewan, there is heavy reliance on herbicides. The chickpea breeding program at the Crop Development Centre, University of Saskatchewan, has developed chickpea cultivars with resistance to imidazolinone (IMI) class of herbicides. The objectives of this study were: (i) to examine the reaction of four chickpea cultivars – CDC Luna, CDC Corinne, CDC Alma, and CDC Cory - to imazamox, imazethapyr, and a combination of imazamox and imazethapyr under field conditions; and (ii) to examine cultivar responses to IMI applications at different growth stages: 2-4 node, 5-8 node, and 9-12 node stage. Field experiments were conducted over five site years in Saskatchewan, Canada in 2012 and 2013. For each experiment, visual injury ratings, plant height, node, and internode length were recorded at 7, 14, 21, and 28 days after each herbicide application (DAA). Days to flowering (DTF), days to maturity (DTM), number of primary branches, pods per plant, harvest index, and seed yield were additional measurements for elucidating physiological responses. Conventional cultivars, CDC Luna and CDC Corinne, had moderate to severe visual injury scores compared to resistant cultivars, CDC Alma and CDC Cory, with minimal to no visual injury after IMI treatment. Height stopped increasing and node development slowed for conventional cultivars treated with IMI herbicides. This susceptibility to IMI herbicides was also recognized with a delay in the DTF and DTM. Despite significant negative response, CDC Luna and CDC Corinne were able to recover throughout the field season, resulting in no yield loss from IMI treatments. Resistant cultivars CDC Alma and CDC Cory demonstrated no negative response from IMI herbicide application compared with the untreated controls. Growth, in terms of height and node development, DTF, DTM, and yield were not significantly different between IMI treated and control treatments. Resistant cultivars tolerated IMI herbicide at all growth stages tested. These results demonstrate potential for use of IMI herbicides in chickpea, expanding the currently limited options for broadleaf weed control.

Graduation date: 2002

Thesis (Ph. D.)--University of Missouri-Columbia, 2000. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2000. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Several agrochemicals are used for rice production in Brazil; depending on their persistence and toxicity, these substances may cause damage to non-target species and also contaminate water systems. Paddy rice fields are important elements of the landscape in Rio Grande do Sul, potentially helping to sustain regional biodiversity of several invertebrate and vertebrate animal species. Phytoplankton communities are primary producers and the base of most food chains, also working as biological filters in the depuration of water systems. The experiments reported here aimed to verify if the herbicide mix imazapyr+imazapic (Kifix®) and also the isolate components imazapyr and imazapic affect the composition and structure of the phytoplankton community in paddy rice fields, when directly added to the water. The experiment was carried out in the municipality of São Sepé, in the central region of Rio Grande do Sul, Brazil, in the crop year 2011/2012. A randomized block design was used in the experiment (5 x 3) with four repetitions. Principal Response Curve analyses of the data obtained demonstrated that both imazapyr and imazapic may have effects over the composition and abundance of phytoplankton in paddy rice fields. The greatest effects were found on three different taxonomical classes of organisms: Cyanophyceae (cyanobacteria), Chlamydophyceae (unicellular flagellates) and Chlorophyceae (green algae). Moreover, the experimental treatments with herbicide additions resembled the control in the last sampling date, indicating that the substances have a greater toxic effect in the first few days after addition. / A produção de arroz no Brasil utiliza diversos agroquímicos que, dependendo de sua persistência e toxicidade para espécies não-alvo podem contaminar ambientes aquáticos. Lavouras de arroz são parte importante das paisagens do Rio Grande do Sul; são locais de potencial para ajudar a sustentar a biodiversidade regional de muitos invertebrados e vertebrados. O fitoplâncton como produtor primário é a base da cadeia alimentar e desempenha papel de filtro biológico, atuando como estações de tratamento da água nesses ambientes. Objetiva-se com esse trabalho verificar se a mistura herbicida imazapir+imazapique (Kifix®) e os compostos isolados, imazapir e imazapique, alteram a composição e densidade da comunidade fitoplanctônica em lavoura de arroz irrigado, considerando a adição direta dos contaminantes nas parcelas. O experimento foi realizado no município de São Sepé, Depressão Central do Rio Grande do Sul na safra agrícola de 2011/12. O delineamento experimental foi de blocos ao acaso em esquema fatorial (5 x 3) e quatro repetições. Os resultados obtidos pela Curva de Resposta Principal (PRC) demonstraram que os herbicidas imazapir e imazapique usados em lavouras de arroz podem ter efeito sobre a abundância e composição do fitoplâncton. Os maiores efeitos dos herbicidas foram encontrados sobre as populações pertencentes às classes Cyanophyceae, Chlamydophyceae e Chlorophyceae. Além do mais, os tratamentos com herbicidas assemelharam-se ao controle na última coleta constatando que os herbicidas são mais tóxicos nos primeiros dias após a aplicação dos agroquímicos.

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No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) tese_diego_severo_fraga.pdf: 1548587 bytes, checksum: c109de985c27f806698e98816b90240d (MD5) Previous issue date: 2016-03-22 / Sem bolsa / A rotação da cultura da soja ao arroz irrigado e sucessão com azevém pode ser considerado opção para manejo de plantas daninhas em área de terras baixas, principalmente o arroz-vermelho. Além disso, o surgimento de novas tecnologias de soja resistente a herbicidas do grupo das imidazolinonas como a Cultivance® pode auxiliar o produtor de sementes no controle de plantas daninhas quando associadas a sistemas de manejo como “plante-aplique” e “aplique-plante”. Dessa forma, os objetivos da pesquisa foram avaliar a fitotoxicidade, os componentes da produtividade e a qualidade fisiológica das sementes de cultivares de soja contendo as tecnologias Cultivance®, tolerância a sulfonilureias e Roundup Ready®, frente ao resíduo de doses crescentes da mistura dos herbicidas imazapyr e imazapic, aplicado no manejo da cultura do arroz irrigado; avaliar a permanência do resíduo do herbicida no solo em virtude do acúmulo de massa da matéria seca da parte aérea de plantas de azevém, semeadas em sucessão com a cultura da soja; quantificar a atividade da enzima ALS em cultivares de soja resistentes ou suscetíveis ao herbicida imazapic; avaliar as alterações nos metabólitos secundários de plantas de soja contendo essas tecnologias, submetidas a mistura dos herbicidas imazapyr e imazapic nos sistemas de manejo “plante-aplique e “aplique-plante”. Para isso, foram realizados experimentos em campo, casa-de-vegetação e laboratório da Universidade Federal de Pelotas, Embrapa Clima Temperado e Embrapa Trigo, utilizando diferentes cultivares de soja submetidas ao herbicida imazapyr+imazapic. Os resultados demonstraram que a cultivar de soja contendo a tecnologia Cultivance® é resistente a mistura dos herbicidas imazapyr e imazapic aplicado no manejo do arroz irrigado, porém, as demais cultivares são suscetíveis. O resíduo do herbicida afeta a produtividade e a qualidade fisiológica da semente das cultivares estudadas. A massa da matéria seca da parte aérea do azevém, é reduzida na presença do resíduo do herbicida. O KM (concentração de piruvato) da enzima ALS das cultivares de soja são semelhantes, contudo o Vmáx (velocidade máxima da reação) da cultivar resistente é menor, comparado às demais, supondo-se que a resistência da cultivar contendo a tecnologia Cultivance® pode ser decorrente da insensibilidade da enzima ALS ao herbicida imazapic. As cultivares suscetíveis apresentam, em geral, maior teor de clorofila e sofrem maior ação das espécies reativas de oxigênio, comparadas a resistente. A elevação da dose da mistura dos herbicidas imazapyr e imazapic aumenta a ação do sistema antioxidante enzimático, por meio das enzimas superóxido dismutase, catalase e ascorbato peroxidase, independente do sistema de manejo. / Soybean crop rotation with irrigated rice and sucession with ryegrass may be considered an option to weed management in flooded area, mainly for red rice. Besides that new technologies appearance of soybean herbicide resistant of imidazolinone group such as Cultivance® may help seed farmers in the weed control when associated to management systems such as “plant-apply” and “apply-plant”. Thus the reseach objectives were evaluate phytotoxicity, yield components and physiological quality of soybean seeds’ cultivars containing Cultivance®, sulfonylurea tolerant and Roundup Ready® technologies, as affected by carryover of increasing doses of mixture of herbicides imazapyr and imazapic spraying in management of irrigated rice crop; evaluate herbicide carryover in soil due ryegrass shoot dry matter, seeded in sucession with soybean crop; quantify ALS enzyme activity in soybean cultivars resistants or susceptibles to imazapic herbicide; evaluate the changes on secondary metabolism of soybean plants containing these technologies, submmited to mixture of herbicides imazapyr and imazapic in “plant-apply” and “apply-plant” management systems. Therefore experiments were performed on field, greenhouse and laboratories in the Federal University of Pelotas, Embrapa Temperate Climate and Embrapa Wheat, using differents soybean cultivars submmited to imazapyr+imazapic herbicide. The results showed that soybean cultivar containing Cultivance® technology is resistant to mixture of herbicides imazapyr and imazapic sprayed in management of irrigated rice, but the others cultivars are susceptibles. The herbicide carryover affect the crop yield and physiological quality of seed of the studied cultivars. Ryegrass shoot dry matter is affected by herbicide carryover. ALS enzyme KM (pyruvate concentration) of soybean cultivars are similar, however the Vmáx (maximum reaction speed) of resistant cultivar is minor, compared with the other cultivars, supposing that the resistance of the cultivar containing Cultivance® technology may be due insensibility ALS enzyme to imazapic herbicide. The susceptibles cultivars show, in general, more chlorophyll and suffer more action of reactives oxygen species, compared to resistant. The increasing dose of mixture of herbicides imazapyr and imazapic enhance the action of enzymatic antioxidant system, by means of superoxide dismutase, catalase and ascorbate peroxidase enzymes, independent of management system.

La première partie de ce travail est consacrée à l'étude et à l'extension de la réaction de Devasia. Un nombre important de structures d'imidazolinones-5 insaturées-4, non accessibles directement par d'autres voies est ainsi réalisé. Le mécanisme de cette réaction et sa catalyse sont étudiés. Les structures des produits sont confirmées par les méthodes spectrométriques et analytiques habituelles. La stéréochimie des composés est déterminée en particulier par R.M.N.1H et 13C. La réactivité des molécules vis-à-vis de plusieurs réactifs est abordée. Au second chapitre nous décrivons une nouvelle voie d'accès à des delta-2-imidazolines polysubstituées et fonctionnalisées originales. La réaction est appliquée aux composés alpha-bromés alpha, bêta-insaturés possédant une fonction carbonylée ou nitrile. L'étude de cette réaction nous a permis de mettre en évidence un mécanisme particulier présentant des intermédiaires non classiques. La structure tridimensionnelle des molécules est déterminée par R.M.N.1H, 13C, dipolmétrie, CNDO-2 et cristallographie. La troisième et dernière partie traite de l'application de la réaction précédente, étendue au cas des amidines non substituées. Elle constitue dans ce cas une nouvelle voie d'accès aux (3H) pyrimidinones-4-disubstituées-2,6. Les structures moléculaires sont déterminées par les méthodes spectroscopiques et analytiques courantes. La réactivité des molécules est alors étudiée vis-à-vis de plusieurs réactifs. En particulier le réarrangement de type Dimroth concernant les (N-éthoxyméthylène et N-formylidène hydrazino)-4 (3H) pyrimidines est abordé et discuté.