Dissertations / Theses on the topic 'Imidazolinone herbicides'

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.

Repeated use of acetolactate synthase (ALS)-inhibiting herbicides in recent years has resulted in the selection of 89 weed species resistant to these herbicides. One management strategy that can eliminate or slow the development of resistance is applying mixtures of herbicides with different modes of action. This research involved the characterization of ALS-inhibiting herbicide-resistant smooth pigweed (Amaranthus hybridus L.), as well as investigations on weed management programs in corn (Zea mays L.) utilizing mesotrione, a triketone, in mixtures with other herbicides. ALS-inhibiting herbicide-resistant smooth pigweed biotypes were collected from fields in Virginia, Delaware, Maryland, and Pennsylvania to evaluate response to ALS-inhibiting herbicides and to determine the molecular mechanisms of resistance. Sequencing of the ALS genes from these biotypes revealed two amino acid substitutions known to confer resistance, Ala₁₂₂ to Thr and Ser₆₅₃ to Asn, and one that has not been previously reported in plants, Asp₃₇₆ to Glu. The smooth pigweed biotype with an Asp₃₇₆ substitution displayed resistance to four classes of ALS-inhibiting herbicides that included imidazolinone (IMI), sulfonylurea (SU), pyrimidinylthiobenzoate (PTB), and triazolopyrimidine sulfonanilide (TP) chemistries. Transformation of this smooth pigweed ALS gene into Arabidopsis thaliana confirmed that the Asp₃₇₆ substitution is responsible for the resistance. Other biotypes that had a substitution at Ala₁₂₂ exhibited resistance to an IMI herbicide, little to no resistance to SU herbicides, and increased sensitivity to a PTB and a TP herbicide, whereas, biotypes that had a substitution at Ser₆₅₃ exhibited high-level resistance to an IMI herbicide and lower resistance to PTB and SU herbicides. Experiments were also conducted to investigate the effectiveness of mesotrione in preemergence (PRE) and postemergence (POST) corn weed management programs in Virginia. Mesotrione applied PRE in mixtures with S-metolachlor and atrazine controlled common lambsquarters (Chenopodium album L.), smooth pigweed, common ragweed (Ambrosia artemisiifolia L.), and morningglory (Ipomoea spp.) species when a timely rainfall followed application. POST applications of mesotrione controlled common lambsquarters and smooth pigweed, but common ragweed and morningglory species were not always controlled. Common ragweed and morningglory species were controlled by mesotrione in a mixture with atrazine POST. Large crabgrass [Digitaria sanguinalis (L.) Scop.] and giant foxtail (Setaria faberi Herrm.) control was generally better when the ALS-inhibiting herbicides nicosulfuron plus rimsulfuron or rimsulfuron plus thifensulfuron plus atrazine were applied in a mixture with mesotrione. Mixtures of mesotrione with other POST herbicides in a total POST program produced corn yields comparable to standard PRE followed by POST weed management programs.
Ph. D.

Red rice (Oryza spp.) is one of the main limiting factors of rice yield (O. sativa L.) in the world and particularly in the Rio Grande do Sul (RS) state Brazil. The Clearfield® technology is a viable and efficient tool for controlling such harmful plant by using imidazolinone herbicides in tolerant cultivars. However, herbicides may persist on the soil after the crop season in amount that could affect the future use of the area with other crops as well as with non tolerant rice cultivars. The persistence of this kind of herbicides is highly dependent on the soil s environmental conditions. It increases in low pH soils with high organic matter (MO) content, and under anaerobic conditions. The main way of herbicide dissipation is the biodegradations; they can be photolysis or be lixiviated bellow the roots absorption region. Two field experiments were carried out on lowland soil in Santa Maria-RS during 2006/2007. The first experiment (Chapter II) had the objective of determining the effect of nine soil tillages (four on no till or minimum till seeping and five, on conventional tillage) on the phytotoxicity of non tolerant rice. The residual effect of the herbicide Only® affected plants stand, tillering, panicle number and plant heights of cultivar IRGA 417, but did not affect the grain yield. Soil plowing decreased herbicide activity on the soil surface (0-3 cm) without affecting the variables assayed. The second experiment (Chapter III) had the objective of determining the effect of two soil tillages (no till- PD- and conventional tillage-PC) on imazethapyr degradation and leaching. Higher degradation of imazethapyr was registered on PC than on PD. Imazethapyr leaching until 20 cm regardless the tillage system. In PC, a uniform distribution of imazethapyr was observed in the first 15 cm of soil while in PD there was a lower concentration of imazethapyr at 0-5 cm, which accumulated at 5-15 cm deep.
O arroz-vermelho (Oryza spp.) é um dos principais fatores limitantes da produtividade de grãos do arroz irrigado (O. sativa L.) no mundo e em particular do estado do Rio Grande do Sul (RS) Brasil. A tecnologia Clearfield® é uma ferramenta viável e eficiente para o controle desta planta daninha, mediante o uso de herbicidas da família das imidazolinonas junto com cultivares tolerantes a estes herbicidas. No entanto, os herbicidas podem permanecer no solo após o cultivo, em quantidade que pode comprometer a utilização futura da área com outras culturas, ou mesmo com cultivares de arroz não tolerante (NT). A permanência destes herbicidas no solo é muito dependente das condições ambientais e de solo, aumentando sua persistência em solos com pH baixos, com altos conteúdos de matéria orgânica (MO), argila e em condições de anaerobioses. A principal via de dissipação destes herbicidas é a microbiana, podendo também, sofrer fotólises ou serem lixiviados para fora da área de absorção das raízes. Foram conduzidos dois experimentos sob solo de várzea, em Santa Maria-RS no ano agrícola 2006/07. O primeiro experimento (Capítulo II) teve como objetivo determinar o efeito de nove manejos de solo (quatro sob plantio direto ou semidireto e cinco sob plantio convencional), na fitotoxicidade do arroz não tolerante. O efeito residual do herbicida Only® afetou o estande de plantas, perfilhamento, número de panículas e a estatura da cultivar não tolerante IRGA 417, porém não afetou a produtividade de grãos. O revolvimento do solo diminuiu a atividade do herbicida na camada superficial de solo (0-3 cm), embora não tenha afetado as variáveis analisadas. O segundo experimento (Capítulo III) teve como objetivo determinar o efeito de dois manejos de solo, plantio direto (PD) e plantio convencional (PC), na degradação e lixiviação do imazethapyr. Ocorreu maior degradação de imazethapyr no PC do que no PD. Imazethapyr lixiviou até 20 cm, independente do sistema de cultivo. No PC existe uma distribuição uniforme do imazethapyr nos primeiros 15 cm de solo e no PD existe menor concentração de imazethapyr de 0-5 cm, e acúmulo do herbicida de 5-15 cm de profundidade.

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The red rice (Oryza sativa) co-exists with the cultivated rice in commercial farmings, becoming one of the main limiting factors for the yield increase in this crop, since this weed competes for the same resources. The rice crop is one of the most important in the world, being the main nutritious source for more than half of the world´s population. Genes for resistance to herbicides have become the best option for the control of this weed. Herbicides that inhibit the ALS enzyme, such as those from the imidazolinone chemical group, are commonly used for weed control in many crops. These ALS inhibitors are currently used for the control of red rice, which is known as Clearfield® technology. This work aimed to study the morphological features that can assist in identifying Only® herbicide tolerance in hydroponic bioassays, and introgression of ALS inhibitor herbicide tolerance genes in cultivars through artificial hybridizations. The rice cultivars used were BRS Sinuelo CL and Puitá INTA CL as imidazolinone herbicide tolerant, and the BRS Pampa, BRS Querência, BRS Atalanta and BRS Fronteira, as sensitive. The variable insertion of the first leaf can be considered an appropriate candidate for study because it discriminates more effectively the responses of different genetic constitutions. Taking in account the doses and periods of development, it can be recommended for use as a morphological marker. The concentration of herbicide that allows better discrimination between tolerant and sensitive genotypes is 25μg L-1 as described in the methodology for this bioassay. The results of this study show that F2 hybrids resulting from crosses between cultivars carrying the allele for herbicide tolerance to the imidazolinone class and conventional rice cultivars, are feasible, enabling the establishment of populations with desirable agronomic characteristics of herbicidetolerant rice, with higher ability to fight the red rice.
O arroz vermelho (Oryza sativa) co-existe com o arroz cultivado em lavouras comerciais, sendo esse um dos principais entraves para o aumento da produtividade dessa cultura, já que essa invasora compete pelos mesmos recursos que as cultivares necessitam. A cultura do arroz é uma das mais importantes no mundo, considerada a principal fonte nutritiva para mais da metade da população mundial. Genes para resistência a herbicidas têm se tornado uma das opções mais utilizadas no mundo para o controle de invasoras, sendo que os herbicidas inibidores da enzima ALS, classe das imidazolinonas, são amplamente utilizados para o controle de plantas daninhas em diversas culturas. Esses inibidores de ALS são atualmente utilizados para o controle do arroz vermelho, sendo esta tecnologia denominada Clearfield®. Este trabalho objetivou o estudo de características morfológicas capazes de auxiliar na identificação de tolerância ao herbicida Only®, em bioensaio em condições hidropônicas, e a introgressão de genes de tolerância ao herbicida inibidor de ALS em cultivares, através de hibridações controladas. Foram utilizados as cultivares de arroz BRS Sinuelo CL e Puitá INTA CL como padrão tolerante aos herbicidas imidazolinonas, e as cultivares BRS Pampa, BRS Querência, BRS Fronteira e BRS Atalanta, como padrão sensível. A variável inserção da primeira folha pode ser considerada uma variável apropriada para estudos, pois discrimina de maneira mais eficiente as diferentes respostas das constituições genéticas frente às doses utilizadas e aos períodos de desenvolvimento, podendo ser indicada para ser utilizada como marcador morfológico. A concentração de herbicida que possibilita melhor discriminação entre genótipos tolerantes e sensíveis é 25μg L-1, conforme metodologia descrita para esse bioensaio. Os resultados desse estudo mostram que os híbridos F2, resultantes de cruzamentos entre cultivares portadores do alelo de tolerância ao herbicida da classe das imidazolinonas e cultivares de arroz irrigado convencionais, são viáveis, possibilitando o estabelecimento de populações de arroz irrigado tolerantes ao herbicida, com maior capacidade de combater o arroz vermelho e com características de interesse agronômico.

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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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
No cultivo do arroz irrigado as plantas daninhas que apresentam maior importância são: o arroz daninho e capim-arroz. O controle químico é atualmente o principal método de controle destas plantas daninhas. A utilização de cultivares tolerantes aos imidazolinonas possibilita um controle seletivo. A mistura de herbicidas pode proporcionar inúmeras vantagens como redução das doses aplicadas e aumento do espectro de ação. Saflufenacil um herbicida relativamente novo apresenta potencial para ser aplicado em mistura com outros herbicidas. Além disso, ele é indicado para aplicação em pré-emergência com ação residual no solo. O objetivo deste estudo foi verificar a eficiência no controle de arroz daninho e capim-arroz; a seletividade ao arroz irrigado, com o uso de misturas em tanque entre imazapyr+imazapic e saflufenacil; avaliar as interações de misturas entre os dois herbicidas em plantas de arroz daninho, bem como, avaliar possíveis alterações no metabolismo antioxidante durante a germinação em função da aplicação de saflufenacil. Para atingir esses objetivos, foram conduzidos três experimentos; O experimento I foi realizado em campo, utilizou-se o cultivar Puitá INTA CL, os tratamentos foram compostos por aplicação isolada e em misturas de imazapyr+imazapic e saflufenacil. O experimento II foi realizado em casa de vegetação, onde foram aplicados imazapyr+imazapic e saflufenacil, isolados e em misturas, sendo que cada mistura foi constituída sempre por ao menos uma subdose dos herbicidas. Os resultados de controle, redução da estatura de plantas e matéria seca da parte aérea de arroz daninho, foram analisados pelo Método de Colby para verificar o efeito de interação. No experimento III, sementes de soja foram colocadas para germinar em presença de água ou solução herbicida de saflufenacil, e incubadas no escuro ou expostas à luz (fotoperíodo de 14h), seis dias após, avaliou-se as alterações no metabolismo antioxidante e quantificou-se o extravasamento de eletrólitos. Os resultados do experimento I mostraram que saflufenacil não interferiu no percentual de controle de imazapyr+imazapic em capim-arroz e arroz daninho, além de não acarretar perda de produtividade na cultura do arroz. A menor dose de imazapyr+imazapic (36,75+12,25 g e.a. ha-1), isolada e em mistura proporcionou baixo nível de controle destas duas plantas daninhas, reduzindo a produtividade. No experimento II foi constatado um maior número de misturas com efeito de aditividade na interação entre os dois herbicidas. Resultados do experimento III mostram que ocorreu um incremento na atividade da SOD na luz e no escuro em diferentes doses de saflufenacil, maior atividade da CAT na dose de 3,0 μM na luz e no escuro e incremento da APX com 3,0 μM na luz e 6,0 μM na luz e escuro. Os teores de H2O2 foram maiores com saflufenacil na presença de luz, MDA foi elevado apenas na dose de 6,0 μM sob luz. O maior extravasamento de eletrólitos foi observado nos tratamentos com saflufenacil expostos à luz. Os resultados mostram que saflufenacil pode ser utilizado em mistura com imazapyr+imazapic no arroz irrigado, podendo ampliar o espectro de controle de plantas daninhas da cultura sem causar perdas de produtividade. Na ausência de luz saflufenacil causa incremento na atividade do sistema antioxidante, mas não proporciona danos às membranas celulares.
In irrigated rice weeds with the greatest importance they are: weedy rice and barnyardgrass. Chemical control is currently the main method of control of these weeds. The use of cultivars tolerant to imidazolinones allows selective control. The mixture of herbicides can provide many advantages such as reduction of the amount applied and increased spectrum of action. Saflufenacil a relatively new herbicide has the potential to be applied in tank mixture with other herbicides. Moreover, it presents a recommendation for application in pre-emergence residual action in the soil. The objective of this study was to determine the effects on weedy rice control and barnyardgrass; and selectivity to rice by applying mixtures of imazapyr+imazapic with saflufenacil; evaluating the interactions between mixtures of two herbicides in weedy rice plants, as well as to assess possible changes in antioxidant metabolism during germination depending on the application saflufenacil. To achieve these goals, three experiments were conducted; The first experiment was carried out in the field, used the cultivar Puitá INTA CL, the treatments were applied alone and in mixtures of imazapyr + imazapic with saflufenacil. The second experiment was conducted in a greenhouse, where they were applied imazapyr+imazapic and saflufenacil, alone and in mixtures, each mixture was always consists of at least one sub-dose of herbicides. The results of control, reduced height and shoot dry mass of weedy rice were analyzed by Colby’s Method to check the effect of interaction. In the experiment III, soybean seeds were germinated in the presence of water or solution herbicide saflufenacil, and incubated in the dark or exposed to light (photoperiod of 14h), six days after was evaluated the changes in antioxidant metabolism and quantified the electrolyte leakage. The results of experiment I show that saflufenacil doesn’t interfere in the percentage of imazapyr + imazapic control in barnyardgrass and weedy rice, besides not causing loss of productivity in the rice crop. The lowest dose imazapic+imazapyr (36.75 + 12.25 g a.e. ha-1), alone and in mixture provided low level control of two weeds, reducing productivity. In experiment II was observed a greater number of mixtures additivity effect on the interaction between the two herbicides. Experiment III results show that there was an increase in the activity of SOD in the light and in the dark at different doses of saflufenacil, higher CAT activity at a dose of 3,0 μM in light and dark and increased APX with 3,0 μM in the light and 6,0 μM in light and dark. The H2O2 levels were higher with saflufenacil in the presence of light, MDA was raised only at the dose of 6,0 μM under light. The highest electrolyte leakage was observed in treatments with saflufenacil exposed to light. The results show that saflufenacil may be used in tank mixture with imazapyr+imazapic in irrigated rice, which can extend the weed control spectrum culture without causing productivity losses. In the absence of light saflufenacil causes increased activity of the antioxidant system, but doesn’t give damage to cell membranes.

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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.

Studies were conducted in 1996 through 1999 to: (1) evaluate the responses of one imidazolinone (IMI)-susceptible (S) and four -resistant (R1, R2, R3, and R4) smooth pigweed populations to various acetolactate synthase (ALS)-inhibiting herbicides, (2) determine the mechanism of resistance, and (3) evaluate the relative growth and competitiveness of each population. Field studies were conducted in 1996 near Marion, MD, in a field with a history of repeated imazaquin use. Smooth pigweed control with IMI herbicides was < 8 percent, but control with sulfonylurea (SU) herbicides ranged from 73 to 99 percent. Follow-up greenhouse studies were used to confirm IMI resistance in the Marion, MD smooth pigweed population (R4) as well as three others (R1, R2, and R3). R populations were 730- to 1350-fold more tolerant to imazethapyr than the S population. Based on resistance ratios, all R populations displayed low-level cross-resistance to chlorimuron and negative cross-resistance to thifensulfuron, pyrithiobac, and cloransulam-methyl with R2 being the most sensitive of the R populations to pyrithiobac and cloransulam-methyl. Absorption, translocation, and metabolism of ¹⁴C-cloransulam-methyl in S and R2 populations were generally similar. Three metabolites of cloransulam-methyl with ratio of front (Rf) values approximately 0.83, 0.65, and 0.45 were isolated. The metabolite with a 0.83 Rf value increased over time as the parent molecule decreased indicating that it plays a major role in cloransulam-methyl metabolism in smooth pigweed. The other metabolites did not change significantly over time and never represented more than 5 percent of the extracted radioactivity. The identity of these metabolites has not been determined. Using enzyme assays, it was determined that IMI resistance in R populations was due to an altered ALS that was no longer susceptible to inhibition by these herbicides. ALS from S, R1, and R2 populations responded similarly to chlorimuron and thifensulfuron, but reductions in enzyme activity by chlorimuron and thifensulfuron were significantly greater for R3 ALS than for S, R1 or R2 ALS. ALS from R2 and R3 was significantly more sensitive to inhibition by pyrithiobac compared to S ALS. Based on resistance ratios, R2 and R3 ALS were also more sensitive to inhibition by cloransulam-methyl than S ALS. Negative cross-resistance to thifensulfuron, pyrithiobac, and cloransulam-methyl in some R populations at the whole-plant level can be explained by increased sensitivity at the enzyme level. Under noncompetitive conditions in the greenhouse, S produced 17, 23, 25, and 44 percent more biomass than R1, R2, R3, and R4 populations, respectively. S plants were also taller than R plants 17 and 21 d after planting (DAP) and displayed a faster initial rate of leaf area increase compared to all R populations. The net assimilation rate of S was significantly higher than R2 and R3 populations 24 DAP. R3 and R4 populations had significantly less chlorophyll per g of plant tissue compared to S; therefore, reduced growth in some R populations compared to S may be linked to chlorosis that generally appears early in seedling development. Biomass production in the field under competitive conditions was similar for all populations using both monoculture and mixed populations. For this reason, the differences in growth observed in the greenhouse in the S population may not confer a competitive advantage over R populations in the field.
Ph. D.

Red rice (Oryza spp.) is one of the main limiting factors to rice (O. sativa L.) yield. After several decades searching for red rice control tools, it was developed imidazolinone tolerant rice, to selectively control red rice. To better understand this technology it were conducted two experiments in 2004/05, in Santa Maria, Rio Grande do Sul state, Brazil. The first experiment (Chapter I) had the objective of: 1) evaluate red rice control by imidazolinone herbicides in Clearfield rice; 2) evaluate the imidazolinone herbicide carryover effect on rygrass and non-tolerant rice (IRGA 417) and 3) evaluate the outcrossing rates between Clearfield rice and red rice. The herbicides tested control red rice. Although injury to Clearfield rice was observed, the herbicide did not affected yield. It was observed herbicide carryover to non-tolerant rice, reducing plant stand. There was natural outcrossing between Clearfield rice and red rice, at rates of 0.065%. The second experiment (Chapter II) had the objective of evaluate the herbicide Only® (imazethapyr 75 g L-1 + imazapic 25 g L-1) in different application rates and timing on two genotypes, IRGA 422 CL and Tuno CL, to the imidazolinones herbicides. When compared with the cultivar, the hybrid was more tolerant to the herbicide Only®. It was possible to apply rates of up to 2.0 L ha-1 in the hybrid, without affecting rice yield. Red rice control was total with split application of Only® in PRE and POST, with rates above 1.25 L ha-1. The most efficient treatment was with application of 0.75 L ha-1 in PRE followed by 0.5 L ha-1 in POS, because, it was the lowest rate that promoted 100% control, with relatively low toxicity to the cultivar and without affecting rice yield.
O arroz-vermelho (Oryza spp.) é um dos principais fatores limitantes da produtividade de grãos do arroz irrigado (O. sativa L.). Após várias décadas de busca de alternativas para o controle seletivo do arroz-vermelho, desenvolveram-se genótipos de arroz tolerante a herbicida do grupo químico das imidazolinonas, o qual controla eficiente e seletivamente esta planta daninha. Para estudar e melhor entender esta tecnologia, conduziu-se dois experimentos em Santa Maria-RS no ano agrícola 2004/05. O primeiro experimento (Capítulo I) teve como objetivos: 1) avaliar a eficiência do controle de arroz-vermelho com o herbicida Only? (imazethapyr 75 g L-1 + imazapic 25 g L-1), 2) avaliar o residual do herbicida no solo através dos danos causados no azevém e em arroz não tolerante e 3) avaliar a taxa de ocorrência de cruzamento natural entre o arroz-vermelho e o arroz cultivado. O herbicida testado controla eficientemente o arroz-vermelho em arroz tolerante. Embora tenha-se observado fitotoxicidade, não houve redução na produtividade da cultivar tolerante. O estande inicial da cultivar IRGA 417 é afetado pelo residual do herbicida presente no solo. Ocorre cruzamento natural entre o arroz-vermelho e o arroz cultivado, sendo que a taxa de ocorrência obtida no experimento foi de 0,065%. O segundo experimento (Capítulo II) teve como objetivo avaliar o controle de arroz-vermelho e o desempenho de dois genótipos de arroz irrigado, IRGA 422 CL e Tuno CL, tolerantes a herbicidas do grupo das imidazolinonas a doses e épocas de aplicações do herbicida Only? , em áreas com alta infestação de arroz-vermelho. Constata-se que o híbrido é mais tolerante ao herbicida Only? , quando comparado à cultivar IRGA 422 CL, sendo possível a utilização de dose total de até 2,0 L ha-1 no híbrido, em áreas com alta infestação de arroz-vermelho, sem afetar a produtividade. O controle de arroz-vermelho é total com aplicação fracionada do herbicida em pré e pós-emergência (PRE + POS), desde que o total aplicado não seja inferior a 1,25 L ha-1. Esta condição é atendida pelo tratamento com 0,75 L ha-1 em PRE mais 0,5 L ha-1 em POS, o qual propicia a menor dose total dentre aqueles com 100% de controle, não afetando a produtividade e com fitotoxicidade semelhante ao tratamento com 1,0 L ha-1 em POS, utilizado como referência.

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O objetivo do trabalho foi desenvolver metodologia rápida e eficiente para identificação de sementes de arroz-vermelho resistente aos herbicidas inibidores da enzima acetolactato sintase e avaliar o tempo para superação da dormência de sementes de arroz-vermelho. Utilizaram-se dois biótipos de arroz-vermelho, sendo um resistente (General Câmara, RS) e outro suscetível (Cachoeirinha, RS) a imazapir + imazapic (Kifix®), herbicida inibidor da acetolactato sintase, e duas cultivares de arroz, Puitá INTA CL e IRGA 417, resistente e suscetível, respectivamente. Para a avaliação da dormência, as sementes de arroz-vermelho foram obtidas no Centro Agropecuário da Palma (CAP), UFPel, Capão do Leão. Os resultados demonstraram que o substrato papel mata-borrão é o mais eficiente para a diferenciação de biótipos quanto a suscetibilidade. A utilização de óleo mineral promove incremento na eficácia do herbicida, independente do biótipo. A dose de 60% da dose comercial é a mais indicada a ser utilizada. As sementes de arroz-vermelho suscetível e a cultivar IRGA 417 apresentaram suscetibilidade ao herbicida do grupo químico das imidazolinonas, enquanto os biótipos arroz-vermelho resistente e Puitá INTA CL demonstraram alta resistência a essa classe de herbicida. A utilização de herbicida diminuiu a porcentagem de plântulas normais de todos os biótipos utilizados. O biótipo de arroz-vermelho resistente apresentou maior germinação e vigor que os demais, seguido do Puitá INTA CL. Variações na temperatura de germinação, abaixo da considerada ótima, reduzem a germinação de sementes de arroz e arroz-vermelho. As sementes de arroz-vermelho coletadas no Centro Agropecuário da Palma apresentaram alta dormência, sendo que 60 dias após a coleta não foram suficientes para a superação total desta condição.
The objective was to develop a methodology for quick and efficient identification of red rice seeds resistant to herbicides inhibiting acetolactate synthase and time to break dormancy of seeds of red rice. Used two biotypes of red rice, one resistant (General Câmara, RS) and a susceptible (Cachoeirinha, RS) to imazapic + imazapyr (Kifix®), acetolactate synthase-inhibiting herbicide, and two rice cultivars, Puitá INTA CL and IRGA 417, resistant and susceptible, respectively. For the evaluation of dormancy, the seeds of red rice were obtained from the Agricultural Center of Palma (CAP), UFPel, Capão do Leão. The results showed that the substrate blotter paper is the most efficient for the differentiation of susceptibility biotypes. The use of mineral oil promotes an increase in the effectiveness of the herbicide, regardless of the biotype. The dose of commercial 60% of the dose is more appropriate to be used. The seeds of red rice and susceptible cultivar IRGA 417 showed susceptibility to the herbicide of the imidazolinone chemical group, while biotypes resistant red rice and Puitá INTA CL showed high resistance to this class of herbicide. The use of herbicide decreased the percentage of normal seedlings of all cultivars. The biotype resistant red rice showed higher germination and vigor than the others, followed by the Puitá INTA CL. Variations in germination temperature below the considered optimal, reduce germination of rice and red rice. The seeds of red rice collected in the Agricultural Center of Palma showed high numbness, and 60 days after collection were not enough to overcome this condition overall.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico
Este trabalho constou de três experimentos, sendo dois em condições de campo e um em sala de crescimento. No experimento 1, conduzido a campo, os herbicidas foram aplicados em pré-emergência do milho, sendo avaliados os seguintes tratamentos: imazethapyr + imazapyr (78,7 + 26,2; 89,2 + 29,7; 69,9 + 35,1; e 79,2 + 39,8 g/ha), imazethapyr + imazapic (70,0 + 35,1; e 79,2 + 39,8 g/ha), imazapic + imazapyr (60,6 + 30,4; 70,0 + 35,1; 68,2 + 22,7; e 78,7 + 26,2 g/ha), atrazine + metolachlor (1.200,0 + 1.800,0 g/ha) e duas testemunhas (com e sem capina). No experimento 2, também conduzido a campo, foram avaliados os tratamentos: imazethapyr + imazapyr (57,7 + 19,2; 68,2 + 22,7; 78,7 + 26,2; 51,2 + 25,7; 60,5 + 30,4; e 69,9 + 35,1 g/ha), imazapic + imazapyr (41,9 + 21,0; 51,2 + 25,7; 60,5 + 30,4; 47,2 + 15,7; 57,7 + 19,2; e 68,2 + 22,7 g/ha), nicosulfuron (48,0 g/ha) e duas testemunhas (com e sem capina), sendo os herbicidas aplicados em pós-emergência do milho. Esses dois experimentos foram conduzidos durante o ano agrícola 1997/98, em Viçosa, no Estado de Minas Gerais, visando avaliar a seletividade de misturas prontas de herbicidas do grupo das imidazolinonas sobre a cultura do milho IMI-Corn, tolerante a esses herbicidas, e sua eficiência no controle de diferentes espécies de plantas daninhas. No ano de 1998 foram aplicadas, a campo, algumas misturas prontas de herbicidas do grupo das imidazolinonas, que mostraram resultados promissores quando aplicadas em pré-emergência [imazethapyr + imazapyr (89,2 + 29,7 g/ha), imazapic + imazapyr (70,0 + 35,1 e 78,7 + 26,2 g/ha)]. Com as amostras de solo coletadas em cinco épocas das diferentes parcelas onde foram aplicadas as misturas de herbicidas e da parcela-testemunha sem herbicida foi conduzido, em condições de sala de crescimento, um bioensaio no qual foi utilizado como planta-teste o sorgo (Sorghum bicolor (L.) Moench), BR 007 (experimento 3), com o objetivo de avaliar o efeito residual das misturas de herbicidas utilizadas. As amostras de solo foram coletadas aos 0, 30, 60, 90 e 120 dias após a aplicação dos tratamentos (DAA). Os resultados obtidos permitiram concluir que o milho IMI- Corn foi tolerante a todas as misturas de herbicidas aplicadas, nas doses avaliadas, tanto em pré como em pós-emergência. As misturas de herbicidas mostraram ser muito eficientes no controle de Cyperus rotundus, Ipomoea grandifolia e Brachiaria plantaginea, mas foram pouco eficientes no de Brachiaria decumbens. Aos 120 DAA, nenhuma das três misturas aplicadas a campo afetou o desenvolvimento das plantas de sorgo, indicando o fim da ação residual no solo dessas misturas de herbicidas.
This work consisted of three experiments, two in the field and one in a laboratory. In the first field experiment (pre emergence) was studied the following treatments: imazethapyr + imazapyr (78.7 + 26.2; 89.2 + 29.7; 69.9 + 35.1; and 79.2 + 39.8 g/ha), imazethapyr + imazapic (70.0 + 35.1; and 79.2 + 39.8 g/ha), imazapic + imazapyr (60.6 + 30.4; 70.0 + 35.1; 68.2 + 22.7; and 78.7 + 26.2 g/ha), atrazine + metolachlor (1,200.0 + 1,800.0 g/ha) and controls (with and without weeding). In the second field experiment (post emergence), the following treatments were stablished: imazethapyr + imazapyr (57.7 + 19.2; 68.2 + 22.7; 78.7 + 26.2; 51.2 + 25.7; 60.5 + 30.4; and 69.9 + 35.1 g/ha), imazapic + imazapyr (41.9 + 21.0; 51.2 + 25.7; 60.5 + 30.4; 47.2 + 15.7; 57.7 + 19,2; and 68.2 + 22.7 g/ha), nicosulfuron (48.0 g/ha) and two controls (with and without weeding). Both experiments were conducted during the 1997-98 agricultural year in Viçosa, Minas Gerais to evaluated the selectivity of pre- mixed herbicides from the imidazolinonas group on IMI-Corn and their efficiency on several weeds control. Pre-mixed imidazolinonas group herbicide mistures which shown promising results at pre-emergence [imazethapyr + imazapyr (89.2 + 29.7 g/ha), imazapic + imazapyr (70.0 + 35.1 and 78.7 + 26.2 g/ha)], were applied to field plots. Soil samples from these treated plots were collected at five periods, 0, 30, 60, 90 and 120 days after herbicides application (DAA), and utilized for one biossay with Sorghum bicolor (L.) Moench, in growth labs with the light, temperature and relative humidity controlled. IMI-Corn was tolerant to all applied pre-mixed herbicide rates at both pre and post emergence. The herbicide mixtures were effective to control Cyperus rotundus, Ipomoea grandifolia and Brachiaria plantaginea, but not Brachiaria decumbens. At 120 DAA, none of the three applied field mixtures had affected sorghum plants growth, indicating the end of soil herbicide residual effect.
Não foi localizado o cpf do autor.

O arroz vermelho (Oryza sativa L.) é a principal planta daninha da cultura do arroz e o seu controle em lavouras comerciais é difícil. As cultivares de arroz resistentes aos herbicidas imidazolinonas proporcionaram o controle seletivo do arroz vermelho. Porém, nos últimos anos surgiram populações de arroz vermelho resistentes a estes herbicidas. Os objetivos desta pesquisa foram elucidar a importância do fluxo gênico e da seleção independente como processos de origem da resistência de arroz vermelho aos herbicidas imidazolinonas no RS; quantificar o fluxo gênico a partir de plantas de arroz vermelho resistentes para plantas de arroz vermelho suscetíveis em condições de cultivo; avaliar a ocorrência de fluxo gênico entre populações de arroz vermelho no RS; e identificar alterações na adaptação de arroz resistente a estes herbicidas baseado no padrão da germinação de sementes. Foram utilizadas 176 indivíduos de arroz vermelho resistentes e suscetíveis aos herbicidas imidazolinonas coletadas no RS e as cultivares IRGA 417, IRGA 422 CL, Sator CL e Puita INTA CL. A origem da resistência foi avaliada baseada em quatro marcadores moleculares single sequence repeats (SSR) e três single nucleotide polimorfism (SNP). O fluxo gênico entre plantas foi realizado em ensaio à campo e a avaliação foi realizada com marcadores fenotípico resistência a imidazolinonas e molecular SNP. O fluxo gênico entre lavouras foi avaliado em 27 populações através de 24 marcadores SSR. A alteração na adaptação de plantas de arroz resistentes foi realizada com base em parâmetros germinativos relacionados à resistência a imidazolinonas. A resistência devida ao fluxo gênico a partir de cultivares resistentes ou à seleção da mutação pelo uso contínuo destes herbicidas ocorreu em 98,9% e 1,1% dos indivíduos, respectivamente. A taxa média de fluxo gênico entre plantas foi de 0,0243%. O arroz vermelho foi mais receptivo ao pólen (0,0344%) que à cultivar IRGA 417 (0,0142%). Baseado no FST de 0,26 encontrado para as populações estudadas o índice estimado de fluxo gênico Nm foi de 0,7. A estruturação populacional indicou haver fluxo de sementes entre lavouras de arroz. As cultivares resistentes alcançaram 50% de germinação em menos tempo que a cultivar suscetível IRGA 417. Estes resultados sugerem que o manejo do arroz vermelho deve ser baseado na redução da pressão de seleção devida ao uso contínuo de herbicidas imidazolinonas e principalmente na mitigação do fluxo gênico de pólen e sementes.
Red rice (Oryza sativa L.) is the most important weed in the paddy field rice, and its control in large scale fields is difficult. The imidazolinone herbicide resistant rice cultivars provide selective red rice control. However, in recent years have been emerged red rice populations resistant to these herbicides. This study aimed to elucidate the relative importance of the gene flow and independent selection as origin process to the imidazolinone resistance in red rice; to quantify the gene flow among imidazolinone resistant red rice and susceptible red rice plants in paddy field conditions; to evaluate the occurrence of the gene flow among red rice populations in RS state; to identify variations in fitness of the imidazolinone resistant rice plants based on the seed germination pattern. Plant material consisted of 176 red rice individuals resistant and susceptible to the imidazolinone herbicides collected in RS and the rice cultivars IRGA 417, IRGA 422 CL, Sator CL and Puita INTA CL. The origin of the resistance was determinate based on four simple sequence repeats (SSR) and three single nucleotide polymorphism (SNP) molecular markers. The gene flow among red rice plants was studied in a paddy field experiment and the evaluation was based on the imidazolinone resistance trait and three SNP molecular markers. In addition, a gene flow among red rice 27 populations was carried out based on 24 SSR molecular markers. The variation in fitness of the resistant rice plants was based on the germination parameters related to the imidazolinone resistance. The imidazolinone resistance origin due to gene flow from resistant cultivars and from independent mutation selection occurred in 98,9% and 1,1% of the individuals, respectively. The mean gene flow rate among plants was 0,0243%. Red rice was more receptive to pollen (0,0344%) than the susceptible cultivar IRGA 417 (0,0142%). Based on the FST of 0,26, the estimated gene flow index Nm was 0,7. The population structure indicated that there is seed flow among rice paddy fields. All the imidazolinone resistant cultivars reached 50% of germination faster than the susceptible cultivar IRGA 417. These results suggest that the management of the red rice should be based on reduction of the selection pressure due to the continuous use of the imidazolinone herbicides and mainly on the mitigation of the seed and pollen gene flow.

O arroz vermelho (Oryza sativa L.) é a principal planta daninha da cultura do arroz irrigado. Por pertencer à mesma espécie da planta cultivada, o controle pela utilização de herbicidas é dificultado. O desenvolvimento de cultivares de arroz resistentes aos herbicidas imidazolinonas proporcionou o controle seletivo do arroz vermelho. Porém o uso contínuo desta tecnologia resultou no surgimento de biótipos resistentes a esses herbicidas. A presente pesquisa teve como objetivos identificar biótipos de arroz vermelho resistentes aos herbicidas imazethapyr + imazapic em diferentes estádios do ciclo de desenvolvimento do arroz e estabelecer técnica para identificação do mecanismo de resistência utilizando marcadores moleculares do tipo ‘single nucleotide amplified polimorfism’ (SNAP). Os bioensaios realizados em sementes, plântulas e afilhos discriminaram de forma efetiva e rápida os indivíduos resistentes e suscetíveis, sendo desta forma, considerados técnicas expeditas no diagnóstico da resistência. As concentrações discriminadoras aos herbicidas imazethapyr + imazapic para os bioensaios de sementes, plântulas e afilhos foram 0,01 mM, 4 mM e 3 mM, respectivamente. A identificação das sequências nucleotídicas do gene ALS nas cultivares de arroz IRGA 422 CL, SATOR CL e PUITÁ INTA CL indicou que as mutações G654E, S653D e A122T, respectivamente, são as responsáveis pela resistência a esses herbicidas. Estas informações, em conjunto com a sequência nucleotídica que circunda estas mutações, foram utilizadas para desenvolvimento de marcadores SNAP para identificar as possíveis mutações que conferem resistência em arroz vermelho resistente a imidazolinonas. Foram analisadas 481 plantas de 38 populações coletadas nas safras de 2006/07 e 2007/08 como escapes de controle dos herbicidas imazethapyr + imazapic. A análise fenotípica destas plantas indicou que o nível de resistência foi alto, médio e baixo em 12, 37 e 50 % para as populações de 2006/07 e em 32, 50 e 18 % para as populações de 2007/08, respectivamente. Os resultados indicaram que na maioria destas plantas, a resistência aos herbicidas é devida à insensibilidade da enzima ALS, resultante das mesmas mutações encontradas nas cultivares de arroz resistentes. A prevenção à ocorrência de plantas de arroz vermelho resistente aos herbicidas pertencentes ao grupo químico das imidazolinonas deve considerar procedimentos relacionados à diminuição da pressão de seleção causada pelo herbicida.
Red rice (Oryza sativa L.) is the main weed in the paddy field rice. Cultivated rice and red rice belong to the same species, resulting in difficulties for red rice control through herbicides. However, the development of imidazolinone resistant rice cultivars allowed red rice selective control. The continuous use of this technology leads to the occurrence of imidazolinone resistant red rice biotypes. This study aimed to identify red rice plants resistant to the herbicides imazethapyr + imazapic at different stages of rice plant development, as well as, to develop a tool for identifying the resistance mechanism using SNAP (‘single nucleotide amplified polymorphism’) molecular markers. The bioassays used for seeds, seedlings and tillers discriminated resistant and susceptible individuals in a short evaluation period, being considered as a fast method for herbicide resistance diagnostic. The discriminatory concentrations between resistant and susceptible plants to the herbicides imazethapyr + imazapic for the bioassays of seeds, seedlings and tillers were 0,01 mM, 4 mM e 3 mM, respectively. The identification of the ALS gene nucleotide sequences in the resistant rice cultivars IRGA 422 CL, SATOR CL and PUITÁ INTA CL indicated that the mutations G654E, S653D and A122T, respectively, are responsible for the resistance. This information and the nucleotide sequence that surrounds these mutations were used for the development of the SNAP molecular markers to identify the possible mutations that confer the resistance in red rice. This analysis was varied out in a total of 481 plants from 38 populations collected during 2006/07 and 2007/08 seasons as escapes of control of the herbicides imazethapyr + imazapic. A phenotypic analysis in these plants indicated that the resistance level was high, medium and low in 12, 37 and 50 % for the populations of 2006/07 and in 32, 50 and 18 % for the populations of 2007/08, respectively. The molecular results indicated that the majority of these plants are resistant due the insensitivity of the ALS enzyme, caused by the same mutations found in the resistant rice cultivars. The prevention of the herbicide resistance in red rice must consider procedures related to the reduction of the selection pressure caused by the herbicide.

O Brasil cultivou 25,4 milhões de hectares com culturas geneticamente modificadas (GM) em 2010, dos quais 17,8 milhões foram ocupados com soja resistente a herbicidas. Hoje o país já ocupa a posição de segundo maior produtor mundial de soja geneticamente modificada. Em um dos eventos de obtenção de soja transgênica, a engenharia genética desenvolveu plantas pela introdução do gene ahas de Arabidopsis thaliana, que confere tolerância aos herbicidas do grupo químico das imidazolinonas. O gene ahas codifica a proteína AHAS (aceto-hidroxiácido sintase), que é encontrada naturalmente em todas as plantas e que catalisa a primeira etapa da biossíntese dos aminoácidos de cadeia ramificada. Nas plantas convencionais, a inibição da enzima AHAS pelos herbicidas à base de imidazolinona provoca uma deficiência de aminoácidos de cadeia ramificada e de outros compostos derivados dessa via, necessários a sua sobrevivência. Alguns trabalhos têm abordado os impactos ambientais de culturas transgênicas e do uso de herbicidas, contudo, poucos estudos referentes aos efeitos dessas culturas e dos herbicidas na biomassa microbiana do solo foram realizados. O objetivo desta tese foi o de avaliar o impacto da soja geneticamente modificada contendo o gene ahas e do herbicida Imazapyr do grupo das imidazolinonas na microbiota do solo. Ao todo foram avaliados vinte ensaios, conduzidos em três safras e nove municípios localizados em seis estados e no DF com soja convencional (cultivar Conquista) e transgênica (Soja Cultivance, evento 127). Os parâmetros avaliados foram, quantitativamente, o carbono e o nitrogênio da biomassa microbiana, pelo método de fumigação-extração) e a análise qualitativa da diversidade genética da comunidade bacteriana pelo método do DGGE ("Denaturing Gradient Gel Electrophoresis"). As amostras foram coletadas na camada de 0-10 cm no pré-plantio e no estádio R2 do desenvolvimento da cultura. O delineamento experimental foi em blocos ao acaso, com cinco tratamentos (T1: soja Cultivance - evento 127 (soja GM), com controle de plantas invasoras efetuado exclusivamente com herbicida imidazolinona; T2: soja Cultivance, evento 127 (soja GM), com controle de plantas invasoras efetuado com herbicidas convencionais; T3: cultivar parental da qual o evento 127 originou (Conquista) (soja convencional), com controle de plantas invasoras efetuado com herbicidas convencionais; T4: cultivar M-SOY 8001 (soja convencional da Monsoy), utilizada como padrão convencional, com controle de plantas invasoras efetuado com herbicidas convencionais; T5: variedade CD 217 (soja convencional da Coodetec), utilizada como padrão convencional, com controle de plantas invasoras efetuado com herbicidas convencionais), com quatro repetições. O herbicida imidazolinona utilizado foi o Imazapyr na dose de 70 g i.a ha-1 e o convencional consistiu da mistura Bentazon + Acifluorfen-sódio, na dosagem recomendada para cada região. Em todos os ensaios avaliados não foram encontradas diferenças na biomassa microbiana do solo entre os tratamentos que pudessem ser atribuídas aos herbicidas, ou à transgenia. Também não houve efeito da transgenia, ou entre os diferentes herbicidas, na avaliação qualitativa da comunidade bacteriana do solo realizada pelo método do DGGE. Diferenças quantitativas e qualitativas foram atribuídas exclusivamente a diferenças entre locais, a estágios de desenvolvimento das plantas, a diferenças entre cultivares e a condições climáticas.
Brazil had 25.4 million hectares cropped with genetically modified (GM) plants In 2010 from which 17.8 million were occupied with soybean tolerant to herbicides. Nowadays the country is the second largest GM soybeans producer. In one event of genetic engineering GM soybean, a cultivar was developed with the introduction of the gene ahas, from Arabidopsis thaliana, which confers resistent to herbicides of the imidazolinone chemical group. The ahas gene encodes the AHAS protein (aceto-hydroxyacid synthase), which is found naturally in all plants and catalyzes the first step in the biosynthesis of branched chain amino acids. In conventional plants, the inhibition of the enzyme AHAS by herbicides of the group imidazolinone results in a deficiency of the branched chain amino acids and other compounds derived from this pathway necessary for their survival. Some studies have been performed about the environmental impacts of transgenic crops and their specific herbicides; however few studies about the effects of the transgeny and of specific herbicides on soil microbial biomass are available. The objective of this thesis was to evaluate the impact of GM soybean with the gene ahas and of the herbicide Imazapyr of the imidazolinone group on the soil microorganisms. A total of twenty field trials were performed for three crop seasons with the parental conventional (Conquista) and the transgenic (Cultivance) soybean cultivars, in nine cities located in six states and at the Federal District. The parameters evaluated were, quantitatively, the microbial biomass of carbon and nitrogen, determined by the soil fumigation-extraction method, and qualitatively the bacterial community by the method of DGGE (Denaturing Gradient Gel Electrophoresis). Samples were collected at 0-10 cm layer at the pre-planting and the R2 stages of development of culture. The experimental was performed in a completely randomized block design, with five treatments (T1: Cultivance soybean - event 127 (GM soybean), with weed control carried out exclusively with imidazolinone herbicide; T2: soybean Cultivance, event 127 (GM soybean), with weed control carried out with conventional herbicides; T3: parental cultivar from which the event originated 127 (Conquest) (conventional soybeans), with weed control carried out with conventional herbicides; T4: cultivar M-SOY 8001 (Monsoy conventional soybeans), used as a conventional pattern, with weed control carried out with conventional herbicides; T5: CD 217 variety(conventional Coodetec soybean), used as conventional pattern, with weed control carried out with conventional herbicides), and four replications. The imidazolinone herbicide Imazapyr was used at a dose of 70 g i.a ha-1 and the conventional herbicide consisted of a mixture of Bentazon + Acifluorfen-sodium with the recommended dosage for each region. In all trais, no differences in soil microbial biomass were detected that could be attributed to the transgeny, or the herbicides. Also, no effects of the transgeny or of the herbicides could be detected in the qualitative evaluation of bacterial community evaluated by DGGE. Quantitative and qualitative differences were attributed exclusively to the different locations, stage of plant development, genetic differences between cultivars, and climatic conditions.

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A contaminação do solo e de águas com herbicidas tem gerado grande preocupação ambiental. Esta preocupação é ainda maior quando se utiliza estes compostos em áreas de várzeas irrigadas na cultura do arroz. Neste trabalho foram realizados estudos sobre o comportamento dos herbicidas imazethapyr e imazapic muito utilizados na cultura do arroz em todo o Brasil. Foram realizados três experimentos para avaliar a sorção, lixiviação e persistência do imazethapyr e imazapic aplicados em mistura e de forma isoladas em três solos provinietes do estado de Tocantins (Plintossolo Háplico (FX), Latossolo Vermelho-Amarelo (LVA) e Gleissolo Háplico (GX)), com diferentes características físicas e químicas, utilizados para o cultivo do arroz e outras culturas anuais. Para determinação da sorção, lixiviação e persistência dos herbicidas nos solos foram utilizados ensaios biológicos. Constatou-se que a sorção, a lixiviação e a persistência de imazethapyr e imazapic em mistura e isolados, são influenciadas pelas características físicas e químicas dos solos. Maiores teores de óxidos de ferro e menores valores de pH dos solos favorecem a sorção e a persistência do imazethapyr e imazapic. Concluiu-se que aplicações do imazethapyr e imazapic nos solos avaliados representam alto risco de contaminação do solo e das águas por esses herbicidas.
The contamination of soil and water with herbicides has caused major environmental concern. This concern is even greater when using these compounds in lowland irrigated areas in rice. In this work, we studied the behavior of imazethapyr herbicide imazapic and widely used in rice cultivation in Brazil. Three experiments were conducted to evaluate the sorption, leaching and persistence of imazethapyr and imazapic applied in mixture and isolated way in three provinietes soils of the state of Tocantins (Haplic Plinthosol (FX), Oxisol (LVA) and Epiaquic Haplustult (GX)) with different physical and chemical characteristics, used for growing rice and other annual crops. To determine sorption, leaching and persistence of herbicides in soil biological assays were used. It was observed that the sorption, leaching or the persistence of imazapic and imazethapyr alone and in combination, are influenced by the physical and chemical characteristics of the soil. Higher content of iron oxides and lower pH values favor the soil persistence of the sorption and imazapic and imazethapyr. It was concluded that applications of imazethapyr and imazapic in the evaluated soils represent a high risk of soil and water contamination by these herbicides.

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The objective of this research was: a) evaluate the effect of imidazolinone chemical group herbicides on the growth of plants and the injuries to the photosynthetic apparatus of three rice types (varieties) exposed to these and b) evaluate the effect of soil residual herbicides imazethapyr+ imazapic on corn, cucumber, radish and tomato are used as bioindicators. At first experiments we used the herbicide Only® and Kifix®, using a randomized split plot design in a factorial 5x3 with six replications, with the first factor rates corresponded to 0, 5, 10, 15 and 20 mg p. c. m-2 of commercial product Only® and 0, 7, 14, 21 and 28 mg p. c. m-2 of commercial product Kifix®, and factor B type of rice (cultivated rice cv. Puitá Inta CL, red rice ecotype sensitive to herbicides Imidazolinone and red rice ecotype with suspected herbicide tolerance imidazolinone). We evaluated the parameters of chlorophyll a fluorescence, phytotoxicity, plant height and dry mass. Analysis of chlorophyll a fluorescence was performed using a portable fluorometer (HandyPEA, Hanstech). It was concluded that cv. Puitá Inta CL is tolerant to herbicides Only® and Kifix® and can be used in the Clearfield® system and the red rice ecotype with suspected tolerance was tolerant to both herbicides, suffering a low phytotoxity compared to the sensitive ecotype, even using higher doses of the commercial products. The application of chemical herbicides of the imidazolinone group in rice plants cause changes in the photosynthetic metabolism of plants that can be detected by evaluating the emission of chlorophyll a fluorescence transient. The second experiment was conducted in a randomized block experimental design (with) four replicates per treatment. The treatments were the residual effect of herbicide Only® in rice CL plants in the 2006/2007 harvest, at 0, 10, 15 and 20 mg p. c. m-2 doses of commercial product, on four bioindicators: corn, cucumber, radish and tomato. The variables evaluated were: height, dry weight of shoot and root dry mass, with the latter doesn t being performed for the corn plants. Data of biometric variables generated in both experiments were subjected to analysis of variance (p ≤ 0.05) were significant in these models were tested by polynomial regression. Activity was detected in the commercial mixture of residual herbicides imazethapyr +imazapic in soil 1100 days after herbicide application, by use of bioindicators plants.
Este trabalho teve por objetivo: a) avaliar o efeito da aplicação de herbicidas do grupo químico das imidazolinonas sobre o crescimento de plantas e as injúrias causadas ao aparelho fotossintético de três tipos de arroz e b) avaliar o efeito residual no solo dos herbicidas imazethapyr + imazapic sobre as plantas de milho, pepino, rabanete e tomate, utilizadas como bioindicadoras. No primeiro ensaio foram utilizados os herbicidas Only® e Kifix®, utilizando-se para cada herbicida um delineamento experimental de parcelas subdivididas, em esquema fatorial 5x3, com seis repetições, sendo o fator A as doses do herbicida correspondentes a 0, 5, 10, 15 e 20 mg p. c. m-2 do produto comercial Only® e 0, 7, 14, 21 e 28 mg p. c. m-2 do produto comercial Kifix®, e o fator B o tipo de arroz (arroz cultivado cv. Puitá Inta CL, ecótipo de arroz-vermelho sensível aos herbicidas do grupo das imidazolinonas e ecótipo de arroz-vermelho com suspeita de tolerância aos herbicidas do grupo das imidazolinonas). Foram avaliados os parâmetros da fluorescência da clorofila a, fitotoxicidade, altura de plantas e massa seca da parte aérea. A análise da fluorescência da clorofila a foi realizada utilizando-se um fluorômetro portátil (HandyPEA, Hanstech).Conclui-se que a cv. Puitá Inta CL é tolerante aos herbicidas Only® e Kifix®, podendo ser utilizada no Sistema de Produção Clearfield® e que o ecótipo de arroz-vermelho com suspeita de tolerância apresentou tolerância a ambos herbicidas, sofrendo baixa fitotoxicidade em comparação ao ecótipo sensível, mesmo utilizando-se doses superiores as comerciais dos produtos. A aplicação de herbicidas do grupo químico das imidazolinonas em plantas de arroz causa alterações no metabolismo fotossintético das plantas que podem ser detectadas através da avaliação da emissão da fluorescência da clorofila a transiente. O segundo experimento foi conduzido em um delineamento experimental casualizado por bloco, totalizando quatro repetições por tratamento. Os tratamentos avaliados foram o efeito residual do herbicida Only® sob as plantas de arroz CL na safra 2006/2007, nas doses de doses de 0, 10, 15 e 20 mg p. c. m-2 do produto comercial, sobre quatro espécies bioindicadoras: milho, pepino, rabanete e tomate. Foram avaliadas as variáveis: altura de plantas, massa seca da parte aérea e massa seca das raízes, sendo esta última não realizada para as plantas de milho. Os dados relativos às variáveis biométricas gerados em ambos os experimentos foram submetidos à análise da variância (p≤0,05); em sendo significativos, estes foram testados por modelos de regressão polinomial. Foi detectada atividade residual da mistura comercial dos herbicidas imazethapyr+imazapic em solo após 1100 dias da aplicação dos herbicidas, pelo uso de plantas bioindicadoras.

A resistência a herbicidas em capim-arroz (Echinochloa crus-galli (L.) Beauv.) é um problema presente em todas as regiões de produção de arroz irrigado do Sul do Brasil. No entanto, a prevenção e o controle deste problema são dificultados devido ao desconhecimento do mecanismo de resistência aos herbicidas relacionados a este processo. O objetivo deste trabalho foi desenvolver métodos rápidos de diagnóstico da resistência de capim-arroz a imidazolinonas; analisar a ocorrência de metabolização como mecanismo de resistência de capim-arroz aos herbicidas imazethapyr e quinclorac; e avaliar diferentes herbicidas isolados e em associações para controle de biótipos resistentes. Os bioensaios de plântula e perfilhos discriminaram a resistência de capim-arroz a imidazolinonas em sete dias de incubação, em concentrações de imazethapyr ou imazapyr + imazapic de 0,001 e 0,0001 mM, respectivamente. A avaliação do mecanismo de resistência de capim-arroz foi realizada com experimentos em casa de vegetação com aspersão foliar e solução hidropônica e a campo. A ocorrência de incremento de metabolização de herbicidas como mecanismo de resistência foi avaliada pela aplicação de inibidores das enzimas do grupo do citocromo P450 monooxigenases malathion, piperolina butóxido e 1-aminobenzotriazole. Estes inibidores reduziram o fator de resistência a imazethapyr entre 17 e 40% e a quinclorac entre 62 e 120%. Os resultados indicam que o incremento de metabolização está relacionado à resistência de capim-arroz aos herbicidas imidazolinonas em alguns biótipos e com a evolução da resistência a quinclorac em biótipos inicialmente resistentes a imidazolinonas. O experimento a campo de avaliação de controle de capim-arroz resistente a inibidores de ALS indicou maior eficácia dos herbicidas clomazone, profoxydim, fenoxaprop-P-ethyl, propanil, quinclorac e penoxsulam. Associações de fenoxaprop-P-ethyl com inibidores de ALS e profoxydim com quinclorac resultaram em antagonismo no controle de capim-arroz, enquanto que as misturas de quinclorac com imazapyr + imazapic resultou em sinergismo. O incremento de metabolização está associado à resistência múltipla a herbicidas em capim-arroz. Práticas de prevenção de resistência a herbicidas em capim-arroz devem ser empregadas para evitar a distribuição da resistência e, principalmente, da ocorrência de resistência a outros herbicidas.
The resistance to imidazolinone and quinclorac herbicides in barnyardgrass (Echinochloa crus-galli (L.) Beauv.) is a problem in all regions of flooded rice in southern Brazil. However, the prevention and control of this problem is difficult due to the unknown mechanism of herbicide resistance. The objectives of this study were to develop rapid methods for the diagnosis of imidazolinone resistance in barnyardgrass; analyze the occurrence of metabolization enhancement as the mechanism of herbicide resistance of barnyardgrass to quinclorac and imazethapyr, and to evaluate different herbicides alone and in associations for the control of the imidazolinone resistant biotypes. The seedling and tiller bioassays discriminate the imidazolinone resistance in seven days of incubation of imazethapyr or imazapyr + imazapic at concentrations of 0.001 and 0.0001 mM, respectively. The evaluation of the resistance mechanism of barnyardgrass to imidazolinones was performed through experiments conducted in greenhouse with foliar spray and in hydroponic conditions and in the field. The occurrence of herbicide metabolization enhancement as a mechanism of resistance was assessed by the application of inhibitors of the cytochrome P450 monooxygenases, malathion, piperolina butoxide and 1-aminobenzotriazole. These inhibitors reduced the resistance factor of imazethapyr in 17 to 40% and of quinclorac in 62 to 120%. These results indicate that metabolization enhancement is related with the resistance of barnyardgrass to imidazolinone herbicides in some biotypes, and to the evolution of resistance to quinclorac in biotypes initially resistant to imidazolinones. The field experiment indicated the efficient control of the imidazolinone resistant barnyardgrass with clomazone, profoxydim, fenoxaprop-P-ethyl, propanil, quinclorac and penoxsulam. Combinations of fenoxaprop-P-ethyl and ALS inhibitors, and profoxydim and quinclorac resulted in antagonism, while the mixture of quinclorac and imazapyr + imazapic resulted in synergism for the barnyardgrass control. The metabolization enhancement is associated with the multiple herbicide resistance in barnyardgrass. The prevention of herbicide resistance in barnyardgrass must be employed to avoid the increase of the distribution of resistance and especially the resistance to other herbicides.

No presente trabalho, foi avaliada a influência dos monômeros básico (1-vinilimidazol) e ácido (ácido metacrílico) no desempenho sortivo e restrito de polímeros impressos para extração de imazetapir em amostras aquosas e alimentos. Os materiais foram caracterizados por espectroscopia na região do infravermelho, microscopia eletrônica de varredura, análise térmica, análise elementar e dados texturais. Com base nos coeficientes de seletividade relativa (k’), o polivinilimidazol molecularmente impresso mostrou maior seletividade em relação ao imazetapir e alguns compostos estruturalmente semelhantes pertencentes a família das imidazolinonas (imazapique e imazapir) quando comparados ao poli(ácido metacrílico) molecularmente impresso. Considerando o seu melhor desempenho seletivo, os estudos de cinética, isotermas de sorção e parâmetros termodinâmicos foram realizados utilizando o polivinilimidazol. Observou-se que os modelos de pseudo-primeira e pseudo-segunda ordem proporcionaram um adequado ajuste para sorção de imazetapir. Em relação à isoterma de sorção, o modelo de Langmuir-Freundlich de dois sítios apresentou o melhor ajuste para os dados experimentais, sugerindo a existência de locais de sorção com diferentes afinidades. As capacidades máximas de sorção obtidas para o polímero impresso e seu material controle (não impresso) foram de 27,1 e 24,4 mg g-1, respectivamente. De acordo com os parâmetros termodinâmicos obtidos, ΔG (0,96 kJ mol-1), ΔH (-22,81 kJ mol-1) e ΔS (-79,73 J mol-1 K-1), pode-se sugerir que o processo de sorção não é espontâneo, é exotérmico e é acompanhado da diminuição da entropia do sistema. Neste caso, a baixa temperatura favorece a sorção de imazetapir no polímero. Estes dados implicam que o processo de sorção é de natureza física, corroborando com o baixo valor de energia de ativação (21,68 kJ mol-1) determinado a partir da equação de Arrhenius. Após a etapa de caracterização, o polímero impresso foi utilizado como sorvente para extração em fase sólida (SPE) de imazetapir, imazapir e imazapique. A faixa linear para os herbicidas usando o polivinilimidazol impresso foi do limite de quantificação (LQ) até 200 µg L-1 (r² ≥ 0,989), sendo que o LQ para o imazapir, imazapique e imazetapir encontrados foram de 0,29, 0,25 e 0,15 µg L-1, respectivamente. O método de SPE apresentou alto fator de pré-concentração (>92), característica importante para uma fase extratora. A aplicabilidade do método foi realizada fazendo-se análise multi resíduo dos herbicidas em diferentes amostras de águas superficiais e arroz. As recuperações ficaram em torno de 92–104% para águas e 85–107% para as amostras de arroz.
In the present work, the influence of the basic (1-vinylimidazole) and acid (methacrylic acid) monomers on the sorptive and restricted performance of imprinted polymers for the selective for the extraction of imazethapyr in aqueous and food samples was evaluated. The materials were characterized by infrared spectroscopy, scanning electron microscopy, thermal analysis, elemental analysis and textural data. Based on relative selectivity coefficients (k’), the molecularly imprinted polyvinylimidazole showed higher selectivity towards imazethapyr and some structurally similar compounds belonging to the imidazolinones family (imazapic and imazapyr) when compared to the molecularly imprinted poly(methacrylic acid). Considering its better selectivity, sorption kinetics, sorption isotherms and thermodynamic parameters studies were carried out using the polyvinylimidazole imprinted polymer. It was observed that pseudo-first and pseudo-second order models provided the best fit for imazethapyr sorption. Regarding the sorption isotherm, dual-site Langmuir–Freundlich model presented the best fit for the experimental data, thus suggesting the existence of sorption sites with different affinities. The maximum sorption capacities obtained for the imprimted polymer and its control material (non-imprinted) were found to be 27.1 and 24.4 mg g-1, respectively. According to the obtained thermodynamic parameters, ΔG (0.96 kJ mol-1), ΔH (-22.81 kJ mol-1) and ΔS (-79.73 J mol-1 K-1), it might be suggested that the sorption process is non-spontaneous, exothermic and accompanied by decrease in the disorder system. In this case, the low temperature favors the adsorption of imazethapyr on the polymer. These data imply that the adsorption is a process of physical nature, corroborating with the low sorption activation energy (21.68 kJ mol-1) determined from Arrhenius equation. After the characterization step, the imprinted polymer was used as a sorbent for solid phase extraction of imazethapyr, imazapic and imazapyr. The linear range for the herbicides using the printed polyvinylimidazole was from the limit of quantification (LQ) up until 200 μg L-1 (r² ≥ 0,989) and the LOQ for imazapyr, imazapic and imazethapyr were 0.29, 0.25 and 0.15 μg L-1, respectively.The SPE method presented a high preconcentration factor (>92), an important characteristic for an extraction phase. The applicability of the method was carried out by making analysis of the above mentioned herbicides in surface waters from diferent sites and diferent rice samples. The recoveries were about 92-104% for surface water samples and 85-107% for rice samples.

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.
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Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2008

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.

Borage (Borago officinalis) is an annual herb plant for culinary and medicinal uses. Due to a high level of gamma-linolenic acid (GLA) in its seed oil and the health-related benefits of GLA, borage is commercially cultivated. However, a herbicide-resistant variety has not yet been developed for effective weed management in borage farming. Thus, this thesis aimed to create, identify and characterize ethyl methanesulfonate (EMS) induced borage mutants for herbicide imidazolinone resistance. An EMS-mutagenized borage population was generated by using a series of concentrations of EMS to treat M1 seeds. After screening M2 borage plants with the herbicide, tolerant plants were selected, self-pollinated and grown to their maturity. The offsprings were subjected to herbicide screening again to confirm the phenotype, resulting in identification of two genetically stable imidazolinone-resistant lines. Two acetohydroxyacid synthase (AHAS) genes, AHAS1 and AHAS2, involved in the imidazolinone resistance were isolated and sequenced from both mutant (resistant) and wild type (susceptible) borage plants. Comparison of these AHAS sequences revealed that a single nucleotide substitution occurred in the AHAS1 resulting in an amino acid change from serine (S) in the susceptible plant to asparagine (N) in the first resistant line. The similar substitution was later found in the AHAS2 of the second resistant line. A KASP marker was developed for the AHAS1 mutation to differentiate the homozygous susceptible, homozygous and heterozygous resistant borage plants for the breeding purpose. The in vitro assay showed homozygous resistant borage containing the AHAS1 mutation could retain significantly higher AHAS activity than susceptible borage across different imazamox concentrations. The herbicide dose response test showed that the resistant line with the AHAS1 mutation was tolerant to four times the field applied concentration of the “Solo” herbicide.

Weed control in chickpea (Cicer arietinum L.) is challenging because of poor crop competition ability and limited herbicide options. Development of chickpea varieties with resistance to different herbicide modes of action would be desirable. Resistance to imidazolinone (IMI) herbicides in chickpea has been previously identified, but the genetic inheritance and the mechanism were unknown. In many plant species, IMI resistance is caused by point mutation(s) in the acetohydroxyacid synthase (AHAS) gene resulting in an amino acid substitution. This changes the enzyme configuration at the herbicide binding site, preventing the herbicide attachment to the molecule. The main research objective was to genetically characterize chickpea resistance to imidazolinone herbicides. Two homologous AHAS genes, namely AHAS1 and AHAS2 sharing 80% similarity were identified in the chickpea genome. A point mutation in AHAS1 at cytosine 675 thymine 675 resulting in an amino acid substitution from alanine 205 to valine 205 confers the resistance to imidazolinone in chickpea. A KASP marker targeting the point mutation was developed and effectively predicted the herbicide response in the RIL population. This same population was used in molecular mapping where the major locus for herbicide resistance was mapped to chromosome 5. Segregation analysis demonstrated that the resistance is inherited as a single gene in a semi-dominant fashion. To study the synteny of AHAS across plant species, lentil (Lens culinaris) AHAS1 was sequenced. The same mutation that confers the resistance to imidazolinone in chickpea was also found in lentil. Phylogenetic analysis indicated independent clustering of AHAS1 and AHAS2 across pulse species. In vivo and in vitro AHAS enzyme activity analysis showed inhibition of AHAS activity in the susceptible genotype CDC Frontier over time and with the increasing imidazolinone concentrations. In contrast, the resistant genotype CDC Cory did not show AHAS inhibition under the same treatments. In summary, the simple genetic inheritance and the availability of KASP marker could aid in the development of chickpea varieties with resistance to imidazolinone herbicide.