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Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq Brazil is considered the world largest producer of soybeans (Glycine max (L.) Merril). Due to its importance, weed control, such as hairy fleabane (Conyza spp.) should be prioritized, once cases of resistance to the herbicide glyphosate make its control more difficult, requiring new tools to be implemented, such as control cultural associated with the chemical during the off-season. These relationships have not yet been studied from the linear relationships. Therefore, the objective of this study was to evaluate the effects of the integration of cultural and chemical control methods on the hairy fleabane population and its effects on soybean yield using linear relationships. The experiment was conducted at the Federal University of Santa Maria with four replications, during three soybeans crop season: 2018/19, 2019/20 and 2020/21. Cover crop factors (white oat, Ukrainian oat, ryegrass, rye and fallow) and herbicides (2,4-D, metsulfuron-methyl, metribuzin, saflufenacil and control) were used as treatments. The following variables were quantified: hairy fleabane population at stage Z24 and Z29 of cover crops, pre-sowing and soybean V4 and R5 stages, hairy fleabane dry mass, cover crop dry mass, phytotoxicity of herbicides on cover crops, visual control of hairy fleabane, number of soybean plants, soybean plant height, thousand grain weight and soybean yield. Data were submitted to Pearson's linear correlation analysis, cause and effect analysis, Scott-Knott test (p

In view of the rapid evolution of Conyza sumatrensis populations resistant to glyphosate, it is necessary to understand the genetic diversity aimed to improve strategies for managing this weed. We investigated the genetic dissimilarity among 15 biotypes of C. sumatrensis from different geographic regions using microsatellite loci. The biotypes, were cultivated in a greenhouse to obtain vegetal material for DNA extraction. Nineteen microsatellite markers (SSR), were developed for C. sumatrensis biotypes. The genetic dissimilarity was estimated by the Jaccard coefficient (JC) and the biotypes grouped by the UPGMA method. The results demonstrated a high dissimilarity (JC = 7.14 to 82.62) of the analyzed material, with the biotypes forming five groups, being one group formed just by the susceptible biotype and in the others grouped by biotypes from distinct locations in the same group The high genetic diversity of C. sumatrensis indicates that the biotypes may show different responses to different management strategies, and that the mechanisms of resistance to herbicides and characteristics of evolution of populations due to adaptability may be some of the factors involved in the genetic variability of the species. Keywords: polymorphism; SSR; tall fleabane; genetic variability RESUMO: Tendo em vista a rápida evolução das populações de Conyza sumatrensis resistentes ao glifosato, é necessário entender a diversidade genética com vistas a melhorar as estratégias de manejo dessa planta daninha. Diante do exposto, objetivou-se com este trabalho investigar a dissimilaridade genética entre 15 biótipos de C. sumatrensis de diferentes regiões geográficas usando marcadores moleculares microssatélites. Os biótipos foram cultivados em casa de vegetação, para obtenção de material vegetal para extração de DNA. Dezenove marcadores microssatélites (SSR) foram desenvolvidos para os biótipos de C. sumatrensis. A dissimilaridade genética foi estimada pelo coeficiente de Jaccard (JC), e os biótipos, agrupados pelo método UPGMA. Os resultados demonstraram alta dissimilaridade (JC = 7,14 a 82,62) do material analisado, com os biótipos formando cinco grupos. A alta diversidade genética de C. sumatrensis indica que os biótipos podem apresentar distintas respostas a diferentes estratégias de manejo e que os mecanismos de resistência a herbicidas podem ser um dos fatores envolvidos na variabilidade genética das espécies. Palavras-chave: polimorfismo; SSR; buva; variabilidade genética Made available in DSpace on 2021-02-26T12:01:57Z (GMT). No. of bitstreams: 1 0100-8358-PD-38-e020220570.pdf: 449804 bytes, checksum: e87c3ca03e0448545e514f0a87804810 (MD5) Previous issue date: 2020

Biochemical assays in a time-course were employed to evaluate stresses induced by glyphosate treatment in resistant and sensitive biotypes of Conyza bonariensis. Two experiments were conducted assessing glyphosate doses and time-course after treatment. The doses of glyphosate ranged from 0 to 11840 g ae·ha–1 and assessments performed until 552 h after glyphosate treatment (HAT). The objectives of this study were to evaluate the oxidative stress and differential antioxidant enzyme activity in glyphosate-resistant and -sensitive biotypes of hairy fleabane after glyphosate treatment. After treatment, both studied biotypes accumulated similar levels of shikimic-acid until 96 h. The sensitive biotype died at192 HAT. Shikimic-acid and hydrogen peroxide (H2O2) accumulation in glyphosate-resistant biotype were transient and did not differ from untreated plants at 288 and 500 HAT, respectively. In both glyphosate-resistant and -sensitive biotypes, a correlation analysis established a cause-and-effect relationship after glyphosate treatment, which leads to shikimic-acid and hydrogen peroxide accumulation, lipid peroxidation (indicates tissue damage) and an enhancement in the activity of superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) enzyme. However, in the glyphosate-resistant biotype, the oxidative stress and tissue damage were lower, and antioxidant enzyme activities SOD, CAT, and APX were higher than in the -sensitive biotype. It indicates that antioxidant enzyme in glyphosate-resistant biotype might be related to the glyphosate-resistance process in Conyza bonariensis. This study is the first report of differential antioxidant enzyme activity in hairy fleabane.

Submitted by Vinicius Gabriel Caneppele Pereira (viniciuscanepp@gmail.com) on 2019-08-21T17:57:34Z No. of bitstreams: 1 Dissertação Definitiva.pdf: 2483410 bytes, checksum: 2db806c4fbfc94560d7c01e2245458f5 (MD5) Approved for entry into archive by Maria Lucia Martins Frederico null (mlucia@fca.unesp.br) on 2019-08-21T18:14:30Z (GMT) No. of bitstreams: 1 pereira_vgc_me_botfca.pdf: 2483410 bytes, checksum: 2db806c4fbfc94560d7c01e2245458f5 (MD5) Made available in DSpace on 2019-08-21T18:14:30Z (GMT). No. of bitstreams: 1 pereira_vgc_me_botfca.pdf: 2483410 bytes, checksum: 2db806c4fbfc94560d7c01e2245458f5 (MD5) Previous issue date: 2019-07-19 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) A resistência de plantas daninhas a herbicidas é um problema que tem se agravado nos últimos anos, principalmente devido a seleção de biótipos resistentes de buva (Conyza spp.) a importantes herbicidas no manejo destas plantas daninhas, como é o caso do paraquat. Este herbicida atua no aparato fotossintético das plantas, desviando elétrons no fotossistema I, o que leva a formação de espécies reativas de oxigênio (EROs), causando reações oxidativas e morte das plantas. Neste contexto, o objetivo deste trabalho foi caracterizar o comportamento das plantas de Conyza sumatrensis resistentes frente à biótipos suscetíveis ao paraquat, com relação a adaptabilidade ecológica e respostas à ação do herbicida. Ensaios para a caracterização da resistência dos biótipos foram conduzidos através de curvas dose-resposta, a fim de identificar o fator de resistência destas plantas ao paraquat, selecionando-se o biotipo mais resistente para estudos posteriores (FR: 184,71). Foram conduzidos experimentos de adaptabilidade ecológica da espécie, sem a aplicação do herbicida, avaliando-se variáveis morfológicas das plantas como acúmulo de biomassa seca, área foliar, altura das plantas, densidade e tamanho de estômatos além de parâmetros relacionados a fluorescência das plantas (ETR, Fv/Fm). Um terceiro experimento foi conduzido com os mesmos biótipos, trabalhando-se com duas doses de paraquat (0 e 800 g i.a ha-1), a fim de avaliar variáveis fisiológicas no período de 2, 4 e 24 horas após a aplicação (HAA). Algumas plantas foram coletadas 4 HAA para a realização de análises bioquímicas de enzimas antioxidantes da planta como SOD, CAT, APX, POX e MDA. Os dados obtidos foram submetidos à análise de variância pelo teste F (p≤0,05) e as médias comparadas pelo teste de tukey (p≤0,05) calculando-se o intervalo de confiança. Os biótipos resistentes ao paraquat quando na ausência do herbicida, naturalmente apresentaram maior acúmulo de biomassa seca e área foliar, além de maior taxa de assimilação liquida de CO2 (A), eficiência de carboxilação (EC), condutância estomática (gs) e eficiência no uso da água (EUA). Estes biótipos apresentaram maior densidade estomática tanto na face adaxial quanto na face abaxial das folhas, no entanto apresentam estômatos menores com relação ao biotipo suscetível. A taxa de transporte de elétrons (ETR) e o rendimento quântico máximo do fotossistema II (Fv/Fm) foram similares entre os biotipos resistentes e suscetível, porém quando houve a aplicação de 800 g i.a ha-1 de paraquat, apenas os biótipos resistentes apresentaram recuperação 16 HAA. As plantas resistentes apresentaram maior atividade natural das enzimas CAT, SOD, APX, e menor acúmulo de MDA após a aplicação. Os biótipos de C. sumatrensis além de apresentarem elevado fator de resistência, demonstram diferenças morfológicas, fisiológicas e bioquímicas com relação às plantas suscetíveis, além de demonstrarem rápida recuperação dos efeitos deletérios causados pela aplicação de paraquat. The weeds resistance to herbicides is a problem that has worsened in recent years, mainly due to the selection of resistant fleabane biotypes (Conyza spp.) to important herbicides in the management of these weeds, as is the case of paraquat. This herbicide acts on the photosynthetic apparatus of plants, diverting electrons from photosystem I, which leads to the formation of reactive oxygen species (ROS), causing oxidative reactions and plant death. In this context, the objective of this study was to characterize the behavior of resistant Conyza sumatrensis plants in relation to the paraquat susceptible biotypes, in terms of ecological adaptability and responses to herbicide effect. Resistance characterization tests were carried out through dose-response curves (assay 1) to identify the resistance factor of these plants to paraquat, selecting the most resistant biotype for later studies (FR: 184,71). Ecological adaptability experiments were carried out without herbicide application (assay 2), evaluating plant morphological variables such as accumulation of dry biomass, leaf area, plant height, stomata density and size, as well as parameters related to plant fluorescence (ETR, Fv/Fm). A third experiment was carried out with the same biotypes, two doses of paraquat (0 and 800 g ha-1) were applied, in order to evaluate physiological variables at 2, 4 and 24 hours after application (HAA). Some plants were collected 4 HAA to perform biochemical analyzes of plant antioxidant enzymes such as SOD, CAT, APX, POX and MDA. The data were submitted to analysis of variance by the F test (p≤0.05) and the means were compared by the tukey test (p≤0.05), and the confidence interval was calculated. The biotypes resistant to paraquat when in the absence of the herbicide, naturally presented greater accumulation of dry biomass and leaf area, besides higher CO2 assimilation rate (A), carboxylation efficiency (EC), stomatal conductance (gs) and water use efficiency (WUE). These biotypes presented higher stomatal density on both the adaxial and abaxial sides of the leaves, but generally present smaller stomata in relation to the sensitive biotype. The electron transfer rate (ETR) and the quantum efficiency of photosystem II (Fv/Fm) were similar between resistant and susceptible biotypes, but when 800 g i.a ha-1 of paraquat were applied, only the resistant biotypes recovered 16 HAA. Resistant plants showed higher natural activity of CAT, SOD, APX, and lower accumulation of MDA after application. C. sumatrensis biotypes, besides showing a high resistance factor, also demonstrated morphological, physiological and biochemical differences in relation to susceptible plants, as well as showing a rapid recovery of deleterious effects induced by paraquat application.

Submitted by Jonas Leandro Ferrari (jonas.ferrari@unesp.br) on 2020-02-15T17:59:57Z No. of bitstreams: 1 DISSERTAÇÃO DEFINITIVA - JONAS LEANDRO FERRARI.pdf: 5157531 bytes, checksum: 1e14df33f04894bfc645399815e94420 (MD5) Approved for entry into archive by Maria Lucia Martins Frederico null (mlucia@fca.unesp.br) on 2020-02-17T11:25:48Z (GMT) No. of bitstreams: 1 ferrari_jl_me_botfca.pdf: 5157531 bytes, checksum: 1e14df33f04894bfc645399815e94420 (MD5) Made available in DSpace on 2020-02-17T11:25:48Z (GMT). No. of bitstreams: 1 ferrari_jl_me_botfca.pdf: 5157531 bytes, checksum: 1e14df33f04894bfc645399815e94420 (MD5) Previous issue date: 2019-07-19 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) A Conyza sumatrensis é uma das espécies de plantas daninhas de maior importância no Brasil, devido à alta competividade aos recursos naturais essenciais para as culturas, além da resistência ao glyphosate, principal herbicida utilizado no manejo de plantas daninhas em pós-emergência. Em decorrência disto, tem sido comum a mistura em tanque de glyphosate com outros herbicidas, com o intuito de obter controle eficaz da C. sumatrensis. Desta forma, o objetivo deste trabalho foi avaliar o controle de Conyza sumatrensis por flumioxazin, sulfentrazone e glyphosate aplicados isoladamente, de glyphosate + flumioxazin e glyphosate + sulfentrazone, bem como o efeito da interação de tais herbicidas em mistura. Para tanto, foram conduzidos dois experimentos em casa de vegetação, sendo que no experimento 1, os tratamentos foram constituídos por diferentes doses de flumioxazin, sulflentrazone e glyphosate aplicados isoladamente, por doses de flumioxazin + glyphosate (900 g e.a. ha-1) e doses de sulfentrazone + glyphosate (900 g e.a. ha-1). No experimento 2, os tratamentos foram constituídos por diferentes doses de glyphosate aplicado isoladamente, por doses de glyphosate + flumioxazin (50 g i.a. ha-1) e doses de glyphosate + sulfentrazone (600 g i.a. ha-1). O controle foi avaliado por notas visuais de controle aos 4, 7, 14, 21 e 28 dias após a aplicação (DAA) e matéria seca da parte aérea (MSPA) aos 28 DAA. Foi determinado curvas de dose-resposta pelo ajuste da equação dos dados coletados utilizando modelo log-logístico. O efeito da interação das misturas foi avaliado conforme o controle. Observou- que a aplicação de flumioxazin, em pós-emergência, proporciona controle inexpressivo de C. sumatrensis. A aplicação de sulfentrazone, na dose de 600 g i.a. ha-1 em pós-emergência, proporciona controle insuficiente ou bom de C. sumatrensis. A aplicação de glyphosate proporciona controle insuficiente do biótipo de C. sumatrensis em estudo, evidenciando resistência a esse herbicida. A associação de flumioxazin em mistura em tanque de glyphosate não proporciona aumento considerável no controle de C. sumatrensis. A associação de sulfentrazone em mistura em tanque de glyphosate proporciona antecipação e aumento do controle de Conyza sumatrensis. Conyza sumatrensis is one of the most important weed species in Brazil, due to the high competitiveness of natural resources essential for crops, in addition to resistance to glyphosate, the main herbicide used in the management of weeds in post-emergence. As a result, it has been common tank mixing of glyphosate with other herbicides, in order to obtain effective control of C. sumatrensis. Thus, the objective of this work was to evaluate the control of C. sumatrensis by flumioxazin, sulfentrazone and glyphosate applied alone, by doses of glyphosate + flumioxazin and glyphosate + sulfentrazone, as well as the effect of the interaction of such herbicides in mixture. For this purpose, two experiments were carried out in a greenhouse, being the experiment 1, the treatments consisted of different doses of flumioxazin, sulflentrazone and glyphosate applied alone, by doses of flumioxazin + glyphosate (900 g a.e. ha-1) and doses of sulfentrazone + glyphosate (900 g a.e. ha-1). In experiment 2, the treatments consisted of different doses of glyphosate applied alone, by doses of glyphosate + flumioxazin (50 g a.i. ha-1) and doses of glyphosate + sulfentrazone (600 g a.i. ha-1). The control was evaluated by visual injury rating at 4, 7, 14, 21 and 28 days after application (DAA) and dry matter of the aerial part (MSPA) at 28 DAA. Dose-response curves were determined by the adjustment of the collected data equation using a log-logistic model. The effect of the mixtures interaction was evaluated according to the control. It was observed that the application of flumioxazin, in post-emergence, provides inexpressive control of Conyza sumatrensis. The application of sulfentrazone, at a dose of 600 g a.i. ha-1 in post-emergence, provides insufficient or good control of C. sumatrensis. The application of glyphosate provides insufficient control of the C. sumatrensis biotype under study, observing resistance to this herbicide. The association of flumioxazin in tank mixing of glyphosate does not considerable increase the control of C. sumatrensis. The association of sulfentrazone in tank mixing of glyphosate provides anticipation and increased control of Conyza sumatrensis.

Resistance to herbicides is one of the main factors responsible for weed control failures. Once uncontrolled and stressed, resistant weeds demand a new application of herbicides from different modes of action, which results in higher monetary costs and environmental impact. Knowledge of weed sensitivity levels to herbicides before making decisions for their management in the field is paramount to increasing the efficiency of integrated weed management. Thus, methods that allow the rapid determination of sensitivity levels can help to the correct recommendation before the application, and thus, favor the greater technical, economic and environmental efficiency of weed management. The objective of this work was to validate a rapid method to detect the levels of sensitivity of black picker (Bidens pilosa) and horseweed (Conyza sumatrensis) to saflufenacil. Dose-response experiments were performed in growth chamber, greenhouse and field. The control provided by different doses of the saflufenacil herbicide was evaluated in each environment, and the results correlated within each species. The results showed a significant positive correlation for the results obtained in growth chamber and greenhouse for black picker and horseweed. These results indicate that the method developed in the growth chamber can replace greenhouse tests for determination of the sensitivity of black picker and horseweed to saflufenacil.

Made available in DSpace on 2019-11-21T00:35:06Z (GMT). No. of bitstreams: 1 ID447612019v37e019217909PlantaDaninha.pdf: 2438016 bytes, checksum: 305a4655633d97c6c86309d97ceb1347 (MD5) Previous issue date: 2019

Glyphosate-resistant hairy fleabane [Conyza bonariensis (L.) Cronq.] is one of the most important weeds in the world. Among the factors that make this weed species widely distributed in the most diverse environments is the high seed production capacity and dispersal. Hairy fleabane plants not controlled by herbicide application regrowth and overcome crop canopy, use environmental resources, interfere with crops, and complete their life cycle by producing thousands of seeds and replenishing the seed bank. Management strategies that reduce production and viability of hairy fleabane seeds can be adopted within the integrated management to reduce the seed bank and prevent further infestations. In this way, experiments were carried out in a greenhouse and laboratory of seed analysis to evaluate the effect of glyphosate (1,480 g a.e. ha-1) on the production and viability of glyphosate-resistant hairy fleabane seeds when applied at the vegetative and reproductive stages. Seed production was reduced by 68.4 and 100% when glyphosate was applied on hairy fleabane plants at the vegetative and early reproductive stages, respectively, regarding to the control. The viability of hairy fleabane seeds was not influenced by treatments at the evaluated stages. However, glyphosate treatment reduced the hairy fleabane seed production when applied at the vegetative stage . Hairy fleabane seed production is not feasible when glyphosate is applied at the early reproductive stage. RESUMO: A buva [Conyza bonariensis (L.) Cronq.] resistente ao glyphosate é uma das principais plantas daninhas do mundo. Um dos fatores que fazem com que esta planta esteja amplamente distribuída nos mais diversos ambientes é sua alta capacidade de produção e dispersão de sementes. Plantas de buva não controladas pela aplicação de herbicidas rebrotam e sobressaem-se ao dossel da cultura, se beneficiam dos recursos do ambiente, interferem com as culturas, completam seu ciclo produzindo milhares de sementes e realimentando o banco de sementes. Estratégias de manejo que reduzam a produção e viabilidade de sementes de buva podem ser adotadas dentro do manejo integrado, a fim de o banco de sementes e prevenir futuras infestações. Foram realizados experimentos em casa de vegetação e em laboratório de análise de sementes com o objetivo de avaliar o efeito da aplicação de glyphosate nos estádios vegetativo e reprodutivo na produção e viabilidade de sementes de buva resistente ao glyphosate (1.480 g e.a. ha-1). Os resultados demonstram que a produção de sementes reduziu em 68,4% e 100% quando o glyphosate foi aplicado em plantas de buva nos estádios vegetativo e início do reprodutivo, respectivamente, em relação a plantas não tratadas. A viabilidade das sementes de buva não foi influenciada pelos tratamentos nos estádios avaliados. Entretanto, a aplicação do glyphosate no estádio vegetativo da buva reduz a produção de sementes. A produção de sementes de buva é inviabilizada quando o glyphosate é aplicado no início do estádio reprodutivo.

The hairy fleabane ( Conyza bonariensis (L.) Cronq.) is among the most problematic glyphosate-resistant weeds to manage around the world. In weed science, molecular approaches such as RNA sequencing (RNA-Seq) and quantitative reverse-transcription polymerase chain reaction (RT-qPCR) have been employed to study molecular responses to glyphosate treatment in Conyza species. Glyphosate treatment leads to reactive oxygen species (ROS) production in plants which could damage the RNA. Degraded RNA is an issue and can compromise further molecular analysis. Thus, the objective of this study was to evaluate whether glyphosate treatment interferes negatively on RNA integrity of glyphosate-resistant and -sensitive hairy fleabane biotypes. Two experiments were performed using glyphosate doses from 0 to 11,840 g a.e. ha-1 and evaluated in a time-course until 288 hours after treatment. The total of 86 RNA samples were evaluated. The RNA integrity was evaluated in a Bioanalyzer 2100 equipment according to RNA integrity number (RIN) scores and electrophoresis gel. The RIN scores ranged from 5.1 to 9.0. Glyphosate doses do not reduce the RIN scores in both glyphosate-resistant and -sensitive biotypes of hairy fleabane. Visual and automatic analysis of electrophoresis gel show suitable results for all RNA samples, with well-defined bands at 28S and 18S positions and no degradation. The results of the analysis indicate that glyphosate treatment does not affect the RNA integrity of glyphosate-resistant and -sensitive biotypes of hairy fleabane until 288 and 192 hours after glyphosate treatment, respectively. The RNA integrity analysis provides useful results to evaluate the RNA condition for further analysis. However, the costs were around US$ 14.25 per sample, considering only reagents. These results are useful for planning future time-course experiments in Conyza spp. after glyphosate treatment. RESUMO: A buva (Conyza bonariensis (L.) Cronq.) está entre as plantas daninhas resistentes ao glifosato mais difíceis de serem manejadas em todo o mundo. Na ciência das plantas daninhas, abordagens moleculares, como o sequenciamento de RNA (RNA-Seq) e a reação da transcriptase reversa da polimerase em tempo real (RT-qPCR), têm sido empregadas para estudar as respostas moleculares ao tratamento com glifosato em espécies de Conyza. No entanto, o tratamento com glifosato leva à produção de espécies reativas de oxigênio (ROS) em plantas, que podem danificar o RNA. A degradação do RNA é um problema e pode comprometer futuras análises moleculares. Assim, o objetivo deste estudo foi avaliar se o tratamento com glifosato interfere negativamente na integridade do RNA de biótipos de buva resistente e sensível ao glifosato. Dois experimentos foram realizados utilizando doses de glifosato de 0 a 11.840 g e.a. ha-1 e avaliados em um tempo de até 288 horas após o tratamento. O total de 86 amostras de RNA foram avaliadas. A integridade do RNA foi avaliada em um equipamento Bioanalyzer 2100 de acordo com escores de número de integridade de RNA (RIN) e em gel de eletroforese. Os escores do RIN variaram de 5,1 a 9,0. Doses de glifosato não reduziram os escores do RIN em biótipos de buva resistentes e sensíveis ao glifosato. A análise visual e automática do gel de eletroforese mostrou resultados adequados para todas as amostras de RNA, com bandas bem definidas nas posições 28S e 18S e sem degradação. Os resultados da análise indicam que o tratamento com glifosato não afeta negativamente a integridade do RNA dos biótipos resistentes e sensíveis ao glifosato da buva até 288 e 192 horas após o tratamento com glifosato, respectivamente. A análise da integridade do RNA fornece resultados úteis. Entretanto, os custos são altos e ficaram em torno de US $ 14,25 por amostra, considerando apenas os reagentes. Esses resultados são úteis para o planejamento de experimentos futuros em Conyza spp. após o tratamento com glifosato.

Submitted by Victor José Salomão Cesco (victorcesco@hotmail.com) on 2018-09-19T14:33:47Z No. of bitstreams: 1 Dissertação Final.pdf: 2148960 bytes, checksum: 61aef01529ec66c58a054f97421fc1c1 (MD5) Approved for entry into archive by Maria Lucia Martins Frederico null (mlucia@fca.unesp.br) on 2018-09-19T16:11:58Z (GMT) No. of bitstreams: 1 cesco_vjs_me_botfca.pdf: 2148960 bytes, checksum: 61aef01529ec66c58a054f97421fc1c1 (MD5) Made available in DSpace on 2018-09-19T16:11:58Z (GMT). No. of bitstreams: 1 cesco_vjs_me_botfca.pdf: 2148960 bytes, checksum: 61aef01529ec66c58a054f97421fc1c1 (MD5) Previous issue date: 2018-07-31 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) O objetivo deste trabalho é avaliar o desempenho vegetativo, fenológico e reprodutivo de biótipos resistente e sensível de Conyza spp. em função de doses de glyphosate. Foram realizados estudos em casa de vegetação no Núcleo de Pesquisas Avançadas em Matologia (NUPAM) UNESP – FCA, Botucatu sendo conduzido em três estudos distintos: (i) identificação de biótipos resistentes e sensíveis; (ii) curvas dose-resposta com a utilização dos biótipos resistente e sensível em função da aplicação das doses de glyphosate; (iii) identificação dos estádios fenológicos e as características reprodutivas dos biótipos resistente e sensível. O primeiro estudo compreendeu a coleta de 15 biótipos à campo e submetidos a aplicação de quatro doses de glyphosate com quatro repetições inteiramente casualisadas para a identificação de biótipos resistentes e sensíveis. Aos 28 dias após aplicação foram avaliados a porcentagem de controle (CR50) e a massa seca de plantas (GR50). O segundo experimento compreendeu o uso dos biótipos resistente e sensível identificados anteriormente e conduzidos em progenitoras (coletadas a campo) e progênie (reproduzidas em casa de vegetação) a uma série de experimentos de dose-resposta com doses e subdoses de glyphosate. Para o experimento com biótipo resistente foram utilizadas 13 doses de glyphosate e 12 para o sensível, com cinco repetições e inteiramente casualisados para ambos. As variáveis analisadas durante o experimento foram: altura de plantas (cm) e número de folhas e ao final do experimento a massa seca de plantas (g). O terceiro estudo foi realizado com as progenitoras dos biótipos resistente e sensível com nove e oito tratamentos respectivamente, com cinco repetições inteiramente casualisados. Foram avaliados durante o experimento a identificação dos estádios fenológicos bolting, primeiro botão floral e abertura do primeiro botão floral e ao final do experimento foram avaliados o número de capítulos por planta, o número médio de sementes por planta e a soma das unidades termais necessárias para o avanço de estádio fenológico. As análises estáticas usadas foram: regressões e intervalo de confiança a 5% de probabilidade pelo teste “t” nos experimentos conduzidos. O biótipo 2 foi o considerado como o biótipo mais resistente e o biótipo 3 como sensível. Incrementos de massa seca foram observados no biótipo sensível progenitor entre as doses de 0,703125 a 22,5 g. e.a. ha-1 e para o biótipo resistente progênie entre as doses de 1,40625 a 45 g. e.a. ha-1. O biótipo resistente apresentou estímulos de crescimento em doses maiores que os apresentados pelo biótipo sensível. O biótipo resistente mostrou-se mais apto para se reproduzir quando submetido a baixas doses de glyphosate.

Submitted by Jorge Silva (jorgelmsilva@ufrrj.br) on 2021-06-22T18:01:07Z No. of bitstreams: 1 2018 - J?ssica Ferreira Louren?o Leal.pdf: 3640609 bytes, checksum: b2e5c8c2623dd5257a0a7c83f3bbec9b (MD5) Made available in DSpace on 2021-06-22T18:01:07Z (GMT). No. of bitstreams: 1 2018 - J?ssica Ferreira Louren?o Leal.pdf: 3640609 bytes, checksum: b2e5c8c2623dd5257a0a7c83f3bbec9b (MD5) Previous issue date: 2018-02-20 CAPES - Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior One of the major problems of today's agriculture is how to control weeds that are resistant to glyphosate. Not Brazil as species Digitaria insularis (sourgrass) and Conyza spp. (fleabane) has been occurring together and with great aggression in soybean properties. Because it is a monocotyledon and a dicotyledone or mechanism of action of the herbicide used for control should be specific for each species. An application of graminicides, inhibitors of the enzyme ACCase, has been the management option of the sourgrass resistant to glyphosate. Already for fleabane the inhibitory herbicides of ALS and the auxin-mimicking are efficient. However, little is known about the use of the two mechanisms of action in sequential applications or in mixtures for species control. The objective of this study was to evaluate the interaction between synergism and antagonism between ACCase inhibitors, ALS and auxin mimics for control applications of D. insularis and Conyza spp. resistant to glyphosate. The experiments were conducted in pots with soil at the Federal University of Rio de Janeiro, Serop?dica / RJ. These were developed in randomized blocks with 4 replicates, divided into 4 cases, case I and II for 3-4 field sourgrass and flowering stage, and case III and IV for construction plants in the 12-15 sheets. The herbicides used were: (A) haloxifop (62,4 g ha-1), (B) chloransulam (40 g ha-1) and (C) 2,4-D dimethylamine salt (1005 g ha- sequential applications were 3, 6 and 12 days. As the applications evaluated when they are planned, there is no proposed phenological stage. Each case consisted of 10 treatments, in case I and III (control, A, C, A + C, sequential A + C and C + A with interval between applications of 3, 6 and 12 days) and the case II and IV (control A, B, A + B, sequential A + B and B + A with interval between applications of 3, 6 and 12 days). At 7 and 35 days and 14 and 35 days after application (DAA) for fleabane and sourgrass respectively, chlorophyll fluorescence and visual symptom analysis were performed and at 35 DAA the plants were collected with dry mass selection of part area and root. The data generated in the experiments were submitted to ANOVA (p

The objective of this study was to evaluate the relative competitive ability of soybean with different development stages of hairy fleabane. Two experiments were conducted in greenhouse, in a completely randomized design. In the experiment it was tested soybean and hairy fleabane competition at different stage of development (rosette and 15 cm height) at the proportions 100:0, 75:25, 50:50, 25:75 and 0:100, and total plant population was 315 plant m-2. The variables evaluated were plant height, leaf area, and shoot dry matter (leaves and stems). Competitive analysis was performed by diagrams and interpreting the competitiveness index. The soybean has greater competitive ability that horseweed for both development stages. The intraspecific competition is more intense for soybean when in hairy fleabane rosette stage, and the competitive relations are equivalent between soybean and hairy fleabane of 15 cm tall. The both hairy fleabane stages were injured in the soybeans competition.

Herbicide resistance can confer lower competitive abilities; however scarse information is available about the photosynthetic performance between glyphosate-resistant and -susceptible hairy fleabane biotypes coming from areas with similar weed management history. Thus, the goal was to evaluate the photosynthetic performance under different light intensities between glyphosate-resistant and -susceptible hairy fleabane biotypes, from RR soybean fields with a similar weed management history. The tested factors were glyphosate resistant and susceptible biotypes and 12 levels of photosynthetic photon flux density. Plants were cultivated in plastic cups, and at the stage of 10-12 leaves they were subjected to treatments with artificial lighting systems. The net photosynthetic rate, stomatal conductance, substomatal CO2 concentration, transpiration rate, instantaneous water use efficiency, light compensation point and quantum yield were evaluated. In all the evaluated photosynthetic parameters, biotype R showed superior characteristics compared to susceptible biotypes, with the exception of the transpiration rate, where there were no differences. The differences between biotypes may not be associated to glyphosate resistance or susceptibility, but to the evolutionary characteristics of the biotypes. RESUMO: A resistência a herbicidas pode conferir menor capacidade competitiva, porém limitadas informações estão disponíveis sobre o desempenho fotossintético entre biótipos resistentes e suscetíveis ao glyphosate provenientes de área com similar histórico no manejo de plantas daninhas. Assim, o objetivo deste trabalho foi avaliar o desempenho fotossintético sob diferentes intensidades luminosas entre biótipos de buva resistente e suscetível ao glyphosate, oriundos de área de lavoura de soja Roundup Ready® com histórico similar de manejo de plantas daninhas. Os fatores testados foram biótipos resistentes e suscetíveis ao glyphosate e 12 níveis de densidade de fluxo de fótons fotossintéticos. As plantas foram cultivadas em copos plásticos e, no estádio de 10-12 folhas submetidas ao tratamento com sistema de luz artificial. Foram avaliados taxa fotossintética líquida, condutância estomática, concentração de CO2 subestomática, taxa transpiratória, eficiência instantânea do uso da água, ponto de compensação de luz e rendimento quântico. Em todos os parâmetros fotossintéticos avaliados, o biótipo R apresentou características superiores comparado ao biótipo suscetível, com exceção da taxa transpiratória, em que não houve diferenças. As diferenças entre biótipos podem não estar associadas à resistência ou suscetibilidade ao glyphosate, e sim às características evolutivas dos biótipos.

portuguesNo Brasil, a buva (Conyza spp.) e uma das principais plantas daninhas devido a resistencia a herbicidas e alta competividade com as culturas. Esta e responsavel por perdas de produtividade em culturas como soja, milho, algodao e trigo cuja implementacao da semeadura direta e a resistencia aos herbicidas favorecem seu estabelecimento. O conhecimento do efeito da temperatura na germinacao permite prever as regioes com maior potencial de colonizacao e auxiliar no manejo. Assim, objetivou-se com este trabalho determinar o efeito da temperatura na germinacao, viabilidade e longevidade de sementes de buva em solo de terras altas. As temperaturas testadas foram 10, 20 e 30oC e os periodos de avaliacao 0, 15, 30, 45 e 60 dias. As sementes foram acondicionadas em saco de malha de nylon (5 x 5cm), distribuidas em 10g de solo de terras altas (Argissolo Vermelho Amarelo, de textura franco-arenosa), e, alocadas em caixas gerbox com solo a profundidade de 0 a 0,5 cm, nas temperaturas descritas. Avaliou-se em percentagem de sementes remanescentes, primeira e segunda contagem de germinacao, plântulas anormais, sementes mortas, dormentes, viaveis e nao viaveis. A semente de buva atinge dormencia secundaria, nas temperaturas de 10, 20 e 30oC e sua qualidade e longevidade sao prejudicadas nas temperaturas de 20 e 30oC. Palavras-chave: dormencia secundaria; profundidade; manejo; qualidade de sementes EnglishIn Brazil, horseweed is one of the most important weeds because of the resistance to herbicides and high competitive for the crops. A large of losses were reported in major crops such as soybeans, wheat and corn, where the use a no-tillage system and the herbicide resistance promote better establishment. A correct understanding of the way temperature influences germination enables the prediction of the regions with the highest potential for colonization by this weed and thus facilitates its control. The objective of this study; therefore, was to discern the ways temperature affected the germination, viability and longevity of horseweed seeds. Testing was done at 10, 20 and 30°C, while evaluation occurred on days 0, 15, 30, 45 and 60. Seeds were packed in a nylon mesh bag (5x5cm), with 10g of upland soil (Yellow Red Argissolo, sandy loam texture), placed in transparent plastic boxes at 0 to 0.5cm soil depth, at the temperatures specified. Percentage of remaining seeds, first and second germination counts, abnormal seedlings, and dead, dormant, viable and non-viable seeds, were assessed. Horseweed seeds achieve secondary dormancy at 10, 20 and 30°C, while their quality and the longevity showed damage at 20 and 30°C temperatures. Key words: secondary dormancy; depth; management; seed quality

portuguesRegistra-se a escolha de plantas secas de Conyza spp como local de oviposicao pela cigarra Quesada gigas (Olivier, 1790). Sao apresentadas questoes da historia natural das cigarras que indicam a impossibilidade dos imaturos completarem seu ciclo de vida nessa especie vegetal. Sao discutidas algumas implicacoes no manejo de culturas onde Q. gigas possui importância economica. Palavras-chave: parica; cafe; buva; bioecologia; controle EnglishThis study recorded the choice of dry plant of Conyza spp as oviposition site by cicada Quesada gigas (Olivier, 1790). We presented issues of natural history of the cicadas that indicate the inability of immatures to complete life cycle in this species of plant. Some implications on cultures where Q. gigas has economic importance are also discussed. Key words: parica; coffee; buva; bioecology; control

Made available in DSpace on 2018-12-11T17:13:45Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-01-01. Added 1 bitstream(s) on 2019-10-09T18:31:09Z : No. of bitstreams: 1 S0103-84782017000900152.pdf: 538469 bytes, checksum: 8274674a73049224f1ac44092fdf811d (MD5) This study recorded the choice of dry plant of Conyza spp as oviposition site by cicada Quesada gigas (Olivier, 1790). We presented issues of natural history of the cicadas that indicate the inability of immatures to complete life cycle in this species of plant. Some implications on cultures where Q. gigas has economic importance are also discussed. Laboratório de Entomologia Universidade Estadual de Goiás (UEG), Câmpus Iporá IDÉIA - Indústria Comércio Pesquisa e Desenvolvimento de Máquinas e Implementos Agrícolas Departamento de Fitossanidade Faculdade de Ciências Agrárias e Veterinárias (FCAV) Universidade Estadual Paulista Júlio de Mesquita Filho (UNESP) Departamento de Fitossanidade Faculdade de Ciências Agrárias e Veterinárias (FCAV) Universidade Estadual Paulista Júlio de Mesquita Filho (UNESP)

The interference of glyphosate resistant hairy fleabane (Conyza bonariensis) has caused yield losses in soybean crop. Knowledge of the economic threshold is an important aspect for the economic management of resistant weeds. Because of it, the interference of the glyphosate resistant hairy fleabane density on the soybean yield loss was evaluated, as well as to estimate the economic threshold. Two experiments were conducted to verify the effect of different weed densities on the yield of two soybean cultivars (BRS Estância and BMX Turbo). Weed density ranged from 0 to 124 plants m-2. The yield of the BRS Estância decreased by 1.4% to the increase of one single plant, while for the BMX Turbo the loss was 25.9%. Soybean yield and economic threshold were lower for the BMX Turbo cultivar compared to the cultivar BRS Estância, which can be attributed to the genotype, competitive ability, weed development stage and/or environment. Increases in crop yield expectation, soybean price and herbicide efficiency reduce the economic threshold, indicating that the adoption of control measures should be taken when the weed density is low. Due to the high cost of hairy fleabane control, it is only feasible at high densities. RESUMO: A interferência de plantas de buva (Conyza bonariensis) resistente ao herbicida glyphosate tem causado perdas de produtividade na cultura da soja. O conhecimento do nível de dano econômico é um importante fator para o manejo econômico de plantas daninhas resistentes na cultura da soja. Para isso, foi avaliada a interferência da densidade de buva resistente ao glyphosate sobre a perda de rendimento da soja, bem como estimado o nível de dano econômico. Dois experimentos foram conduzidos para verificar o efeito de diferentes densidades da planta daninha sobre a produtividade de dois cultivares de soja (BRS Estância e BMX Turbo). As densidades de buva variaram de 0 a 124 plantas m-2. A produtividade do cultivar BRS Estância reduziu 1,4% ao aumento de uma planta, enquanto para o cultivar BMX Turbo a perda foi de 25,9%. A produtividade da soja e o nível de dano econômico foram menores para o cultivar BMX Turbo, em comparação com o cultivar BRS Estância, o que pode ser atribuído ao genótipo, à habilidade competitiva, ao estádio de desenvolvimento da buva e/ou a ambiente. Aumentos na expectativa de produtividade da cultura, no preço da soja e na eficiência dos herbicidas reduzem o nível de dano econômico, indicando que a adoção de medidas de controle deve ser tomada quando a população de buva é baixa. Em função do elevado custo de controle da buva, este somente é viável em altas densidades.

The objective of this work was to evaluate the growth and development of a glyphosate-resistant population of Conyza bonariensis in different sowing dates (autumn, winter, and spring) and in two agricultural environments, based on days or thermal units. Five experiments were performed in two agricultural environments in Brazil: two in the municipality of Não-Me-Toque, in the state of Rio Grande do Sul - with sowings in July and September 2011; and three in the municipality of Santa Cruz das Palmeiras, in the state of São Paulo ‒ with sowings in April, July, and September 2011. In each trial, ten evaluations of the phenological development and total dry mass of C.bonariensis were performed, fitting these variables to a unit of time in days or growing degree days. The phenological development of C.bonariensis had the best adjustment at the base temperature of 8.4oC, and was affected by sowing date and agricultural environment. In autumn, with decreasing temperature and photoperiod, plants are still able to accumulate dry mass, but without floral induction. In spring, with increasing temperature and photoperiod, dry mass accumulation is lower, but phenological development is faster, with significant floral induction. Resumo: O objetivo deste trabalho foi avaliar o crescimento e o desenvolvimento de uma população de Conyza bonariensis resistente ao herbicida glifosato em diferentes datas de semeadura (outono, inverno e primavera) e dois ambientes agrícolas, com base em dias ou unidades térmicas. Foram desenvolvidos cinco experimentos em dois ambientes agrícolas: dois no Município de Não-Me-Toque, RS - com semeaduras em julho e setembro de 2011; e três no Município de Santa Cruz das Palmeiras, SP ‒ com semeaduras em abril, julho e setembro de 2011. Em cada experimento, realizaram-se dez avaliações do desenvolvimento fenológico e do acúmulo de massa de matéria seca total de C. bonariensis, com ajuste das variáveis à contagem de tempo em dias ou graus-dia acumulados. O desenvolvimento fenológico da espécie apresentou melhor ajuste com temperatura basal de 8,4ºC, e foi influenciado pelo ambiente agrícola e pela data de semeadura. No outono, com temperatura e fotoperíodo decrescentes, as plantas permanecem aptas a acumular massa de matéria seca, porém sem indução floral. Na primavera, com temperatura e fotoperíodo crescentes, o acúmulo de massa de matéria seca é menor, mas o desenvolvimento fenológico é mais rápido, com indução floral significativa.

Horseweed (Conyza spp.) is an annual weed, infesting soybean crops in southern Brazil, with chlorimuron-ethyl being one of the most commonly used herbicides for its control. However, in recent soybean harvests, an unsatisfactory control of this weed using this herbicide was observed, generating suspicion regarding the selection of resistant biotypes. The objective of this study was to evaluate the susceptibility of horseweed biotypes to the herbicide chlorimuron-ethyl. Two experiments were conducted in a greenhouse; in the first one, the biotypes were selected selected, and the second experiment was arranged in a 5 x 5 factorial in a completely randomized design with four replications. The treatments used in the preparation of the dose response curves were doses of the herbicide chlorimuron-ethyl (0.0, 1.56, 3.13, 6.25, 12.5, and 25 g ha-1), applied on the five horseweed biotypes at the 3-4 leaf growth stage. The variables evaluated were visual control percentage and shoot dry weight, compared to the control without herbicide application, and plant acetolactate accumulation. It was concluded that there is a differential susceptibility among the biotypes at doses of less than 20 g ha-1 (dose response curves), which indicates low-level resistance. The practical consequences are the indications of chlorimuron-ethyl application at the maximum doses recomended and that the practice of rotating mechanisms of action must be used in the chemical weed management of these areas.

Conyza bonariensis (hairy fleabane) is one of the most problematic and widespread glyphosate-resistant weeds in the world. This highly competitive weed species significantly interferes with crop growth and substantially decreases crop yield. Despite its agricultural importance, the molecular mechanisms of glyphosate resistance are still unknown. The present RNA-Seq study was performed with the goal of identifying differentially expressed candidate transcripts (genes) related to metabolism-based non-target site glyphosate resistance in C. bonariensis. The whole-transcriptome was de novo assembled from glyphosate-resistant and -sensitive biotypes of C. bonariensis from Southern Brazil. The RNA was extracted from untreated and glyphosate-treated plants at several timepoints up to 288 h after treatment in both biotypes. The transcriptome assembly produced 90,124 contigs with an average length of 777 bp and N50 of 1118 bp. In response to glyphosate treatment, differential gene expression analysis was performed on glyphosate-resistant and -sensitive biotypes. A total of 9622 genes were differentially expressed as a response to glyphosate treatment in both biotypes, 4297 (44.6%) being up- and 5325 (55.4%) down-regulated. The resistant biotype presented 1770 up- and 2333 down-regulated genes while the sensitive biotype had 2335 and 2800 up- and down-regulated genes, respectively. Among them, 974 up- and 1290 down-regulated genes were co-expressed in both biotypes. In the present work, we identified 41 new candidate target genes from five families related to herbicide transport and metabolism: 19 ABC transporters, 10 CYP450s, one glutathione S-transferase (GST), five glycosyltransferases (GT), and six genes related to antioxidant enzyme catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD). The candidate genes may participate in metabolic-based glyphosate resistance via oxidation, conjugation, transport, and degradation, plus antioxidation. One or more of these genes might &lsquo, rescue&rsquo, resistant plants from irreversible damage after glyphosate treatment. The 41 target genes we report in the present study may inform further functional genomics studies, including gene editing approaches to elucidate glyphosate-resistance mechanisms in C. bonariensis.

Submitted by IVANA PAULA FERRAZ SANTOS DE BRITO null (ivanapaulaf@yahoo.com.br) on 2016-12-12T11:21:38Z No. of bitstreams: 1 Tese_Ivana Paula Ferraz.pdf: 1609743 bytes, checksum: dabfed03ce3dbb1480947a22a52cddcd (MD5) Approved for entry into archive by Felipe Augusto Arakaki (arakaki@reitoria.unesp.br) on 2016-12-13T12:19:57Z (GMT) No. of bitstreams: 1 brito_ipfs_dr_bot.pdf: 1609743 bytes, checksum: dabfed03ce3dbb1480947a22a52cddcd (MD5) Made available in DSpace on 2016-12-13T12:19:57Z (GMT). No. of bitstreams: 1 brito_ipfs_dr_bot.pdf: 1609743 bytes, checksum: dabfed03ce3dbb1480947a22a52cddcd (MD5) Previous issue date: 2016-11-11 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) A sensibilidade de plantas daninhas a herbicidas frequentemente se apresenta variável, em função de diversos fatores. O herbicida amônio glufosinate tem ação de contato e inibe a atividade da enzima glutamina sintetase, causando dentre outros efeitos, o acúmulo de amônia nos tecidos foliares, sendo esse um bom indicativo da intoxicação das plantas. Desse modo, o objetivo desse trabalho foi identificar a resposta de plantas de Bidens pilosa e Conyza sumatrensis a diferentes doses do herbicida amônio glufosinate, e a variação da sensibilidade em populações das plantas e de suas progênies ao herbicida. Foram realizados três estudos, todos em casa-de-vegetação e repetidos em diferentes momentos. No primeiro estudo, dois experimentos de dose-resposta foram conduzidos, e foram aplicadas sete diferentes doses do herbicida amônio glufosinate (0, 50, 100, 200, 400, 800, e 1600 g ha-1), com quatro repetições, para cada espécie, sendo realizada análise de amônia e avaliações visuais de fitointoxicação. No segundo estudo, de variação de sensibilidade de B. pilosa e C. sumatrensis ao amônio glufosinate, 44 plantas de B. pilosa e 16 de C. sumatrensis foram aplicadas com a dose de 200 g ha-1 do herbicida, sendo nesse momento a região meristemática e folha mais nova de cada planta protegidas com saco plástico para que não recebessem o herbicida e possibilitasse a manutenção das plantas vivas. Dois dias após a aplicação (DAA) realizou-se a análise do teor de amônia, nas folhas expostas à aplicação, e as folhas protegidas foram mantidas nas plantas para que as mesmas se recuperassem do tratamento e produzissem sementes, utilizadas no estudo de sensibilidade de progênies. Ao atingirem o estádio reprodutivo os botões florais das plantas foram protegidos com sacos de papel para evitar a polinização cruzada e garantir a produção de sementes somente por autofecundação. No terceiro estudo, de variação da sensibilidade das progênies de B. pilosa e C. sumatrensis ao amônio glufosinate, progênies de sete das plantas anteriores foram também tratadas com 200 g ha-1 do amônio glufosinate. Foram quantificados os teores de amônia nos tecidos e porcentagens de controle foram avaliadas visualmente. A amônia foi extraída do tecido foliar fresco das plantas das duas espécies e quantificada por espectrofotometria. Foram realizadas avaliações visuais de controle aos 0, 3, 7, 14 e 21 DAA utilizando-se escala visual de notas variando de 0 a 100%. Os dados obtidos foram analisados pelo teste T e ajustados modelos de regressão não-linear. O estudo de dose-resposta demonstrou que o teor de amônia aumenta de forma assintótica com o aumento da dose do herbicida e que a porcentagem de intoxicação das espécies estudadas também aumenta de modo assintótico com o aumento tanto da dose do herbicida quanto do teor de amônia nos tecidos. O segundo estudo, de variação da sensibilidade, demonstrou haver variabilidade entre indivíduos de uma mesma população sensível ao herbicida, para as duas espécies analisadas; e o terceiro, de estudo das progênies, demonstrou que, para Bidens pilosa, as progênies das plantas com as diferentes capacidades de acumular amônia nos tecidos foram similares em termos de nível de acúmulo; no entanto, no caso de Conyza sumatrensis, as progênies de plantas com maior capacidade em acumulá-la, também exibiram maiores teores internos após o tratamento com glufosinate. Para as duas espécies, a variabilidade dos teores internos de amônia para cada progênie foi bastante alta, suplantando as diferenças médias entre as diferentes progênies, indicando pequena herdabilidade dessa característica. The sensitivity of weeds to herbicide is often variable, due to several factors. The glufosinate-ammonium is a contact herbicide and inhibits the activity of the glutamine synthetase enzyme causing, among others, ammonia accumulation in the leaves, an indicator of the plants intoxication. The objective of this study was to evaluate the response of Bidens pilosa and Conyza sumatrensis to different doses of glufosinate ammonium and the sensitivity range of the plants and their progenies to the herbicide. Three studies were conducted, all in a greenhouse and repeated at different times. In the first study, two experiments were conducted to examine the dose-response curve, and the treatments were seven different doses of the herbicide glufosinate ammonium (0, 50, 100, 200, 400, 800, and 1600 g ha-1), with four replicates for each specie. In the second study, which examined the sensitivity range of B. pilosa and C. sumatrensis to glufosinate ammonium, 44 B. pilosa plants and 16 C. sumatrensis plants were sprayed with 200 g ha-1 of the herbicide. At the time of spraying, the meristematic region and the youngest leaf of each plant were protected with a plastic bag so that they would not receive the herbicide, thus keeping the plants alive. At two days after treatment (DAT), an analysis of the ammonium content on the sprayed leaves them was conducted. The protected leaves were kept on the plants enabling to recover from herbicide treatment and to produce seeds used to assess the sensitivity of B. pilosa and C. sumatrensis progenies to glufosinate ammonium. When the plants had reached the reproductive stage, the flower buds were covered with paper bags to prevent cross-pollination and guarantee that only self-pollination would take place. In the third study, the sensitivity range of the progeny of B. pilosa and C. sumatrensis to glufosinate ammonium was investigated; in this experiment, the progenies of seven of the previous plants were sprayed with 200 g ha-1 of glufosinate ammonium. It was measured the ammonium contents in the tissues and herbicide injury to plants was visually assessed. Ammonium was extracted from fresh leaf tissue immediately after leaf collection from the two species, and quantified per spectrophotometry. Evaluations of visual injury were conducted at 0, 3, 7, 14, and 21 DAT using a visual scale with grades ranging from 0 to 100%. The data were analyzed for t test (p≤0,05) and adjusted by non-linear regression models. The dose-response study showed that increase in ammonia content is related to the treatments used, being correlated to toxicity in the two species. The second study, the sensitivity variation showed that there was variability among individuals of the same population, for both species. The progenies study demonstrated that, Bidens pilosa, progeny plants with different capacities to accumulate ammonia in the tissues were similar in terms of buildup level; However, for Conyza sumatrensis, progeny plants with the greatest ability to accumulate it also exhibited higher internal levels after treatment with glufosinate. The variability of internal ammonia levels for each progeny was quite high, for both species, surpassing the average differences between different progenies, indicating low heritability of this characteristic.

Conyza canadensis e C. bonariensis infestam lavouras de ciclo anual e perene em todo mundo. Fatores ambientais, como a presença de compostos químicos específicos podem interferir significativamente na germinação de suas sementes, fato importante para entender a dinâmica de infestação dessas espécies. Este trabalho teve como objetivo avaliar o efeito de presença e ausência de luz, além da sua interação com a adição de nitrato de potássio e ácido giberélico, na germinação de Conyza canadensis e C. bonariensis, na presença e ausência de luz, comparando o comportamento das duas espécies. A germinação ocorreu em substrato umedecido com água, nitrato de potássio (20mM), ácido giberélico (1mM) e nitrato + GA3 (20mM + 1mM, respectivamente). Os tratamentos foram mantidos sob luz (12 horas) ou no escuro. Concluiu-se que as sementes de ambas as espécies são fotoblásticas positivas, não germinando no escuro. A associação de nitrato de potássio + ácido giberélico (20mM + 1mM) não estimularam a germinação das sementes de ambas as espécies, na ausência de luz.AbstractConyza canadensis and C. bonariensis infest crops with annual and perennial life cycle worldwide. Environmental factors, such as the presence of certain chemical compounds, may significantly interfere with the germination of horseweed, which is important to understand the dynamics of infestation of these species. This work aimed to study the effect of potassium nitrate and gibberellic acid on germination of Conyza canadensis and C. bonariensis in the presence or absence of light. The seed germination occurred in substrate moistened with water, potassium nitrate (20mM), gibberellic acid (1mM) and nitrate + GA3 (20mM + 1mM, respectively). The treatments were maintained under light (12 hours) or in darkness. The seeds of both species are photoblastic positive, with no germination in the dark, even in the presence of the chemical compounds studied.