• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 62
  • 12
  • 2
  • 2
  • 2
  • 1
  • Tagged with
  • 91
  • 91
  • 65
  • 63
  • 35
  • 30
  • 30
  • 28
  • 22
  • 20
  • 17
  • 17
  • 14
  • 13
  • 11
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Controle genético da resistência de Capsicum frutescens à Meloidogyne enterolobii /

Diniz, Guilherme Matos Martins. January 2016 (has links)
Orientador: Leila Trevizan Braz / Coorientador: Pedro Luiz Martins Soares / Banca: Bruno Flávio Figueiredo Barbosa / Banca: Rinaldo César de Paula / Banca: Letícia Akemi Ito Pontes / Banca: Sally Ferreira Blat / Resumo: Os nematoides das galhas estão entre os patógenos que mais causam prejuízos em cultivos protegidos de pimentão, destacando-se as espécies Meloidogyne incognita, M. javanica e M. enterolobii. Este último já foi relatado em plantas de Capsicum spp., e vem causando problemas, pois a utilização de genótipos resistentes a outras espécies não é eficaz em seu controle. Estudos relacionados à resistência a esse patógeno, bem como a obtenção de fontes de resistência ainda são escassos, o que dificulta a adoção de programas de melhoramento genético, visando a esse fim. Sendo assim, o presente trabalho teve por objetivo estudar a herança da resistência à M. enterolobii em Capsicum frutescens. O trabalho foi desenvolvido na UNESP-FCAV, Câmpus de Jaboticabal-SP. Para o estudo da herança da resistência, foi realizado o cruzamento entre C. frutescens, resistente a M. enterolobii e uma linhagem de pimenta C24, C. chinense, suscetível a nematoide. A partir desse cruzamento, foram obtidas as gerações F1, F2, RC1 e RC2. Depois de obtidas todas as gerações necessárias para o estudo, as plantas foram inoculadas com 5.000 ovos e juvenis de segundo estádio de M. enterolobii no ato do transplantio. Após 60 dias da inoculação, realizou-se a avaliação da resistência das plantas ao nematoide, coletando-se as raízes e realizando-se os procedimentos de extração dos nematoides em laboratório. A avaliação da resistência das plantas aos nematoides foi realizada com base no fator de reprodução (FR), sendo co... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Root-knot nematode are among the pathogens that cause most damage in pepper crops protected highlighting the species Meloidogyne incognita, M. javanica and M. enterolobii. The latter has been reported in plants Capsicum spp., and causes problems since the use of resistant genotypes other species is not effective as a control. Studies related to resistance to this pathogen as well as obtaining sources of resistance are still scarce, hindering the adoption of breeding programs for this purpose. Therefore, this study aimed to study the inheritance of resistance to M. enterolobii in Capsicum frutescens. The study was conducted at UNESP-FCAV in Jaboticabal-SP. To study the inheritance of resistance was the cross between C. frutescens, resistant M. enterolobii and C24 pepper strain, C. chinense, susceptible to the nematode. From this junction were obtained F1, F2, BC1 and BC2. After obtaining all generations necessary for the study, the plants were inoculated with 5.000 eggs and juveniles of second stage M. enterolobii in transplanting the act. After 60 days of inoculation was performed to evaluate the resistance of plants to nematode collecting the roots and carrying out the nematode extraction procedures in the laboratory. The evaluation of plant resistance to nematodes was performed based on the reproduction factor (RF) is considered FR ≥ 1, and RF susceptible <1 resistant. The data were analyzed by chi-square test five methods of assessing the genes involved in the control beyond the maximum likelihood test for the presence of related environmental effects or polygenes. Genetic analysis showed no dominance and epistasis indicating only additive gene action. The dominance presented tended susceptibility, indicating that resistance is recessive. The number of loci segregating showed that only one gene was involved ... (Complete abstract click electronic access below) / Doutor
22

Distribuição geográfica e custo adaptativo da resistência de Spodoptera frugiperda (J. E. Smith, 1797) (Lepidoptera: Noctuidae) à proteína Vip3Aa20 no Brasil / Geographical distribution and fitness cost of Spodoptera frugiperda (J. E. Smith, 1797) (Lepidoptera: Noctuidae) resistance to Vip3Aa20 protein in Brazil

Amaral, Fernando Semmelroth de Assunção e 06 February 2018 (has links)
A utilização de plantas transgênicas expressando proteínas inseticidas de Bacillus thuringiensis (Bt) tem sido a principal estratégia para o controle da lagarta-do-cartucho Spodoptera frugiperda (J.E. Smith) no Brasil. A resistência de S. frugiperda à proteína Vip3Aa20 foi recentemente isolada e caracterizada em condições de laboratório, a partir de uma população proveniente de Correntina-BA. Para subsidiar programas de Manejo da Resistência de Insetos (MRI), foram realizados estudos para entender a distribuição geográfica da resistência de S. frugiperda à proteína Vip3Aa20 no Brasil, mediante uso de métodos fenotípicos (proteína purificada e folhas de milho Bt) e genotípicos (F1 e F2 screen), além da elucidação da presença custo adaptativo associado à resistência a partir de uma linhagem resistente quase-isogênica. Para o monitoramento com proteína purificada, as médias de sobrevivência na dose discriminatória de 3600 ng Vip3Aa20/cm2 para 10 populações/safra de S. frugiperda das principais regiões produtoras de milho do Brasil, tiveram um aumento em número, no decorrer das safras, para as populações que diferiram da sobrevivência da linhagem SUS, por não sobreposição do I.C. (95%). As larvas sobreviventes deste monitoramento morreram quando transferidas para folhas de milho Bt expressando Vip3Aa20. Não houve sobreviventes no monitoramento da resistência utilizando folhas de milho Bt, para todas as populações avaliadas. As médias de frequência alélica da resistência estimadas pelo método F1 screen foram de 0,0069, 0,0051 e 0,0041 para as populações avaliadas na 2ª safra/2016, entressafra/2016 e 1ª safra/2017 respectivamente. Pelo método F2 screen, as médias de frequência alélica foram de 0,0030, 0,0036, 0,0054 e 0,0042 para as populações da 2ª safra/2016, entressafra/2016, 1ª safra/2017 e 2ª safra/2017 respetivamente. Foram selecionadas 3 linhagens resistentes a Vip3Aa20 pelo método F2 screen, a partir de populações provenientes de Peabiru-PR, São João da Boa Vista-SP e Casa Branca-SP. Pelo teste de complementaridade, o mesmo alelo da resistência que havia sido inicialmente isolado da região de Correntina-BA, foi verificado nestas novas linhagens resistentes selecionadas. Não foi verificada a presença de custo adaptativo associado à resistência de S. frugiperda a Vip3Aa20, além de um maior valor adaptativo de indivíduos heterozigotos mediante avaliação de parâmetros de tabela de vida e fertilidade. Os resultados do presente trabalho comprovaram que o alelo da resistência de S. frugiperda para a proteína Vip3Aa20 está amplamente distribuído nas principais regiões produtoras de milho no Brasil. Este fato aliado à ausência de custo adaptativo da resistência reforçam a necessidade de implementação de estratégias eficientes de MRI para retardar a evolução da resistência de S. frugiperda à Vip3Aa20 no Brasil. / The use of transgenic plants expressing Bacillus thuringiensis (Bt) insecticidal proteins has been the main strategy to control the fall armyworm Spodoptera frugiperda (J.E. Smith) in Brazil. The resistance of S. frugiperda to Vip3Aa20 protein was recently isolated and characterized in laboratory conditions from a Correntina-BA population. In order to subsidize Insect Resistance Management (IRM) programs, studies were carried out to understand the geographical distribution of S. frugiperda resistance to Vip3Aa20 protein in Brazil, through the use of phenotypic (purified protein and Bt maize leaves) and genotypic methods (F1 and F2 screen), in addition, the elucidation of fitness-cost presence associated with resistance from a near-isogenic resistant strain. For the purified protein monitoring, the mean survival at the diagnostic concentration of 3,600 ng Vip3Aa20/cm2 for 10 populations/season of S. frugiperda from the main maize producing regions of Brazil, had an increase in the number of populations with significant difference by non-overlap in the confidence interval (95 %) in relation with our reference of susceptibility. The surviving larvae of this monitoring died when transferred to leaves of Bt maize expressing Vip3Aa20. There were no survivors in resistance monitoring using Bt maize leaves for all populations evaluated. The mean frequency of resistance alleles estimated by the F1 screen method were 0.0069, 0.0051 and 0.0041 for the populations evaluated in the 2nd/2,016, the offseason/2,016 and the 1st/2,017 crop seasons, respectively. By the F2 screen method, the means of allele frequency were 0.0030, 0.0036, 0.0054 and 0.0042 for the populations of the 2nd/2,016, offseason/2,016, 1st/2,017 and 2nd/2,017 crop seasons, respectively. Three Vip3Aa20 resistant strains were selected by the F2 screen method from populations from Peabiru-PR, São João da Boa Vista-SP and Casa Branca-SP. By the complementarity test, the same resistance allele that had been initially isolated from the Correntina-BA region was verified in these new selected resistant strains. The presence of the adaptive cost associated to the resistance of S. frugiperda to Vip3Aa20 was not verified, besides a higher adaptive value of heterozygous individuals through evaluation of life table parameters and fertility. The results of the present work proved that the resistance allele of S. frugiperda for the Vip3Aa20 protein is widely distributed in the main maize producing regions in Brazil. This fact, coupled with the lack of adaptive cost of resistance, reinforces the need to implement efficient IRM strategies to delay the evolution of S. frugiperda resistance to Vip3Aa20 protein in Brazil.
23

Expressão gênica associada à resistência da soja a Piezodorus guildinii / Gene expression associated with soybean resistance to Piezodorus guildinii

Silva, Ana Paula Mendes 07 February 2014 (has links)
A soja é uma cultura de grande importância, movimentando aproximadamente 230 bilhões de dólares em todo o mundo, com produção anual estimada de 267,61 milhões de toneladas. Os percevejos sugadores de sementes são considerados uma das pragas de maior importância para a cultura da soja, sendo as espécies Euschistus heros (E.), Piezodorus guildinii (West.) e Nezara viridula (L.) as mais abundantes no Brasil. O ataque por percevejos causa diversos problemas como o atraso da maturação fisiológica, retenção foliar, perdas no rendimento e diminuição da qualidade e potencial germinativo das sementes. Esses insetos são responsáveis ainda pela transmissão de patógenos, e podem causar alterações na composição de óleos, proteínas e ácidos graxos das sementes. A obtenção de cultivares com resistência genética é indispensável, a fim de minimizar a necessidade de utilização de defensivos agrícolas. Dessa forma, este trabalho identificou genes possivelmente associados à resposta de resistência pela comparação da expressão gênica diferencial entre genótipos de soja resistente (IAC-100) e suscetível (CD-215), a partir da metodologia de sequenciamento de RNA (RNA-Seq). As vagens foram submetidas a dois tratamentos por 24 horas: infestação por percevejos Piezodorus guildinii (West.) e não infestação. Foi utilizado o alinhador STAR contra o genoma hardmasked do phytozome e o pacote cufflinks.Com os resultados das análises dos genes diferencialmente expressos e uma posterior filtragem foi possível identificar 128 genes candidatos, dentre estes: genes relacionados com defesa, metabolismo secundário de produção de terpenos e proteínas LRR de sinalização celular. / Soybeans are an important crop with a world-wide annual production of 267.61 tons, worth 230 billion dollars. Stink bugs are a major soybean pest. The most abundant species in Brazil are Euschistus heros (E.), Piezodorus guildinii (West.) and Nezara viridula (L.). Stink-bug attack causes several problems, including delayed physiological maturity, leaf retention, yield losses, decreased seed quality, and decreased germination potential. The bugs are responsible for transmitting pathogens, and they can cause changes in the oil, protein, and fatty acids composition in the seed. Producing genetically resistant cultivars is critical in order to minimize the need for agricultural pesticides. Our work aims to identify genes associated with the stink-bug resistance response in soybean by comparing differential gene expression between resistant (IAC-100) and susceptible (CD-215) genotypes by analyzing RNA sequencing (RNA-Seq) data. Data was from soybean pods that were subjected to two treatments for 24 hours: infestation by the stink bug Piezodorus guildinii (West.), and non-infestation. STAR aligner was used against the hard-masked genome sequence from Phytozome, followed by analysis using the Cufflinks package. Analysis of the results of the differentially expressed genes and a subsequent filtering identified 128 candidate defense-associated genes, among them, defense-related such as LRR-RLKs and production of secondary metabolites like terpenes.
24

Monitoramento da suscetibilidade de populações de Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) a inseticidas diamidas no Brasil / Monitoring the susceptibility to diamide insecticides in Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) populations in Brazil

Ribeiro, Rebeca da Silva 09 October 2014 (has links)
Spodoptera frugiperda (J.E. Smith) é uma das pragas mais importantes da cultura do milho no Brasil. Vários casos de resistência de S. frugiperda a inseticidas de grupos químicos distintos já foram documentados. A busca contínua de alternativas para o controle de S. frugiperda tem possibilitado o desenvolvimento de novas tecnologias como plantas de milho geneticamente modificadas, e até mesmo a introdução de inseticidas que aliam segurança ambiental e alta atividade inseticida, como o recente grupo das diamidas. Estudos de caracterização e monitoramento da suscetibilidade de S. frugiperda são fundamentais para a implementação de programas de Manejo da Resistência de Insetos (MRI) no Brasil. Com o intuito de se prolongar a vida útil das diamidas, os objetivos deste trabalho foram: (a) caracterizar a suscetibilidade a diamidas em populações de S. frugiperda nas principais regiões produtoras de milho no Brasil na safra 2011/12; (b) monitorar a suscetibilidade de populações de S. frugiperda a chlorantraniliprole e flubendiamide coletadas na cultura do milho em oito estados do Brasil nas safras 2011/12, 2012/13 e 2013/14; (c) estimar a frequência inicial do alelo de resistência a chlorantraniliprole em populações de S. frugiperda. O método de bioensaio para a caracterização da suscetibilidade de populações de S. frugiperda a chlorantraniliprole e flubendiamide foi o de aplicação superficial do inseticida sobre a dieta. As linhas-básicas de suscetibilidade foram definidas para uma população suscetível de referência e cinco populações de campo de S. frugiperda. Posteriormente, foram definidas concentrações diagnósticas para o monitoramento da suscetibilidade para ambos inseticidas em populações de S. frugiperda. As CLs50 estimadas para as populações de S. frugiperda avaliadas variaram de 1,15 a 2,55 ?g de chlorantraniliprole/mL de água [I.A. (ppm)] (variação de 1,4 vezes), e de 1,75 a 4,17 ?g de flubendiamide/mL de água [I.A. (ppm)] (variação de 2,4 vezes). As concentrações diagnósticas de 10 e 32 ?g de chlorantraniliprole/mL e de 100 e 180?g de flubendiamide/mL foram definidas para o monitoramento da resistência. As populações de S. frugiperda apresentaram alta suscetibilidade nas concentrações diagnósticas de chlorantraniliprole e flubendiamide na safra 2011/12. No entanto, foram observadas variações na sobrevivência de 0 a 12,7% para chlorantraniliprole e de 1 a 6% para flubendiamide de acordo com a safra agrícola e localidade. A frequência do alelo resistente a chlorantraniliprole em S. frugiperda estimado pelo método de \"F2 Screen\" foi baixa para a safra 2011/12 (<0,0033). No entanto, aumento significativo na frequência do alelo resistente foi observado nas safras 2012/13 [0,0134 (0,0082 - 0,0198)] e 2013/14 [0,0176 (0,0084 - 0,0277)] em populações testadas, indicando alto risco de evolução da resistência a chlorantraniliprole no Brasil. / Spodoptera frugiperda (J.E. Smith) is one of the most important maize pests in Brazil. Several cases of S. frugiperda resistance to insecticides of different chemical class have been documented. The continuous search for alternatives to control S. frugiperda has enabled the development of new technologies such as genetically modified corn plants, and even the introduction of insecticides that combine environmental safety and high insecticidal activity, such as the recent class of diamides. Baseline studies and monitoring the susceptibility of S. frugiperda to insecticides are fundamental to the implementation of Insect Resistance Management (IRM) programs in Brazil. In order to prolong the lifetime of diamides, the objectives of this work were: (a) characterize the susceptibility to diamides in populations of S. frugiperda collected from major corn-producing regions in Brazil in 2011/12 season; (b) monitor the susceptibility of S. frugiperda populations to chlorantraniliprole and flubendiamide collected in maize in eight states of Brazil in the 2011/12, 2012/13 and 2013/14 growing seasons; (c) estimate the initial frequency of the allele for resistance to chlorantraniliprole in S. frugiperda populations. The baseline susceptibility of S. frugiperda populations to chlorantraniliprole and flubendiamide was determined using the diet surface treatment bioassays. Baselines were defined for a susceptible population and five field populations of S. frugiperda. Subsequently, diagnostic concentrations for monitoring susceptibility to both insecticides were defined. LCs50 estimated for populations of S. frugiperda ranged from 1.15 to 2.55 mg of chlorantraniliprole / mL of water [IA (ppm)] (1.4-fold variation) and 1.75 to 4.17 mg of flubendiamide / ml water [IA (ppm)] (2.4-fold variation). The diagnostic concentrations of 10 and 32 mg of chlorantraniliprole / mL and 100 and 180?g of flubendiamide / mL were defined for the resistance monitoring. The populations of S. frugiperda showed high susceptibility to chlorantraniliprole and flubendiamide in 2011/12 growing season at diagnostic concentrations. However, variations in survival from 0 to 12.7% for chlorantraniliprole and 1 to 6% for flubendiamide were observed based on growing season and location. The frequency of the resistant allele to chlorantraniliprole in S. frugiperda estimated by using \"F2 Screen\" method was low during 2011/12 growing season (<0.0033). However, significant increase in the frequency of the resistant allele was observed in 2012/13 [0.0134 (0.0082 to 0.0198)] and 2013-14 [0.0176 (0.0084 to 0.0277)] growing seasons, indicating a high risk of resistance evolution to chlorantraniliprole in Brazil.
25

Caracterização da suscetibilidade a inseticidas reguladores de crescimento de insetos em populações de Helicoverpa armigera e Spodoptera frugiperda (Lepidoptera: Noctuidae) do Brasil / Characterization of the susceptibility to insect growth regulator insecticides in populations of Helicoverpa armigera and Spodoptera frugiperda (Lepidoptera: Noctuidae) from Brazil

Amado, Douglas 20 June 2017 (has links)
Os reguladores de crescimento de insetos têm sido um dos mais importantes grupos de inseticidas recomendados para o controle de Helicoverpa armigera (Hübner) e Spodoptera frugiperda (J. E. Smith) no Brasil, que são consideradas pragas-chave de vários sistemas de produção agrícola. Para implementar programas de manejo da resistência de insetos, o presente trabalho teve como objetivo caracterizar a suscetibilidade a inseticidas reguladores de crescimento de insetos em populações de H. armigera e S. frugiperda do Brasil. A caracterização das linhas-básica de suscetibilidade de H. armigera a lufenuron e methoxifenozide e de S. frugiperda a methoxifenozide foi realizada com bioensaio de tratamento superficial da dieta artificial com inseticida, utilizando-se lagartas de 3º instar. Foram verificadas baixa variabilidade na suscetibilidade de H. armigera a lufenuron, com DL50 variando de 0,30 a 1,02 &mu;g de i.a./cm2 de dieta, e a methoxifenozide, com DL50 de 2,61 a 8,02 &mu;g de i.a./cm2 de dieta, em populações coletadas em diferentes regiões agrícolas na safra 2013/2014. As doses diagnósticas, baseadas na DL99, foram de 6,36 &mu;g de i.a/cm2 de dieta para lufenuron e 31,10 &mu;g de i.a/cm2 de dieta para methoxifenozide. Foram observadas variações geográfica e temporal na suscetibilidade a lufenuron e methoxifenozide em populações de H. armigera coletadas nas safras de 2013/2014 a 2016/2017; contudo, não foi possível isolar linhagens de H. armigera resistentes a estes inseticidas, mediante o uso de técnicas de \"F2 screen\" e seleção massal. Uma baixa variabilidade na suscetibilidade de S. frugiperda a methoxifenozide foi observada para as populações coletadas na segunda safra de 2016, com DL50 variando de 0,5 a 2,1 &mu;g de i.a/cm2 de dieta. A dose diagnóstica (DL99) para monitoramento da suscetibilidade a methoxifenozide em populações de S. frugiperda foi de 6 &mu;g de i.a/cm2 de dieta. Na 2ª safra de 2016, a sobrevivência das populações de S. frugiperda avaliadas foram baixas, com valores inferiores a 10% na dose diagnóstica. Por outro lado, na 1ª safra de 2017, houve aumento na sobrevivência das populações testadas, atingindo valores de até 62%. A linhagem de S. frugiperda resistente a methoxifenozide selecionada em condições de laboratório apresentou uma baixa razão de resistência (&asymp;5 vezes). Os resultados da presente pesquisa confirmaram a alta suscetibilidade de H. armigera a lufenuron e methoxifenozide e de S. frugiperda a methoxyfenozide. As informações obtidas no presente estudo servirão para a implementação de programas proativos de manejo da resistência a esses inseticidas. / Insect growth regulators have been one of the most important group of insecticides recommended for controlling Helicoverpa armigera (Hübner) and Spodoptera frugiperda (J. E. Smith) in Brazil which are considered key pests of several crop production systems. To implement insect resistance management programs, the objective of this research was to characterize the susceptibility to insect growth regulators in H. armigera and S. frugiperda populations from Brazil. Baseline susceptibilities of H. armigera to lufenuron and methoxifenozide and S. frugiperda to methoxifenozide were conducted with artificial diet overlay bioassays using 3rd instar larvae. There was low variability in the susceptibility of H. armigera to lufenuron, with LD50 ranging from 0.30 to 1.02 &mu;g of a.i./cm2 of diet, and to methoxifenozide, with LD50 of 2.61 to 8.02 &mu;g of a.i./cm2 of diet across populations collected in different agricultural regions in 2013/2014 growing season. The diagnostic doses, based on DL99, were 6.36 &mu;g of a.i./cm2 of diet for lufenuron and 31.10 &mu;g of a.i./cm2 of diet for methoxifenozide. Geographic and temporal variations in susceptibility to lufenuron and methoxifenozide were observed in populations of H. armigera collected from 2013/2014 to 2016/2017 growing seasons; however, it was not possible to isolate resistant strains to these insecticides using F2 screen and massal selection approaches. There was also a low variability in the susceptibility of S. frugiperda to methoxifenozide across populations collected in the 2nd crop season in 2016, with LD50 ranging from 0.5 to 2.1 &mu;g of a.i./cm2 of diet. The diagnostic dose (DL99) for monitoring the susceptibility to methoxifenozide in S. frugiperda populations was 6 &mu;g of a.i./cm2 of diet. In the 2nd crop season of 2016, the survival at diagnostic dose of S. frugiperda populations evaluated was low (< 10%). On the other hand, in the 1st crop season of 2017, there was a significant increase in the survival across the populations tested, with values reaching up to 62% at diagnostic dose. The laboratory-selected resistant strain of S. frugiperda to methoxifenozide showed a low resistance ratio (&asymp;5 times). We confirmed the high susceptibility of H. armigera to lufenuron and methoxifenozide and S. frugiperda to methoxifenozide in Brazil. The information collected in this study will be important for implementing a proactive resistance management programs to these insecticides.
26

Caracterização da suscetibilidade a inseticidas diamidas e espinosinas em populações de Helicoverpa armigera (Lepidoptera: Noctuidae) do Brasil / Characterization of the susceptibility to diamide and spinosyn insecticides in Helicoverpa armigera (Lepidoptera: Noctuidae) populations from Brazil

Pereira, Rogério Machado 22 May 2017 (has links)
O manejo de Helicoverpa armigera (Hübner) no Brasil tem sido baseado principalmente no controle químico. O uso de inseticidas de grupos químicos mais recentes, tais como diamidas e espinosinas, tem sido crescente no controle de H. armigera e de outros lepidópteros-praga que ocorrem em diferentes sistemas de produção de cultivos. Para a implementação de estratégias proativas de manejo da resistência de insetos, os objetivos da presente pesquisa foram (i) caracterizar as linhas-básicas de suscetibilidade a inseticidas diamidas (chlorantraniliprole, cyantraniliprole e flubendiamide) e espinosinas (spinosad e spinetoram) em populações de H. armigera do Brasil; (ii) estimar a frequência inicial de alelo que confere resistência a chlorantraniliprole e spinosad; e (iii) caracterizar o padrão de herança da resistência de H. armigera a flubendiamide e a resistência cruzada com outras diamidas. Inicialmente foram realizadas a caracterização das linhas-básicas de suscetibilidade a inseticidas diamidas e espinosinas em sete populações de H. armigera coletadas na safra 2013/2014. Foram verificadas baixas variações na suscetibilidade a inseticidas diamidas (< 5 vezes) e espinosinas (&asymp; 2 vezes) entre as populações testadas, baseada na DL50. A frequência inicial do alelo que confere resistência de H. armigera a chlorantraniprole, estimada pelo método F2 screen, foi de 0,00694 (IC95%, 0,00018 - 0,02561) em 2014 a 0,04348 (IC95%, 0,01216 - 0,09347) em 2015. Para spinosad, a frequência foi de 0,02632 (IC95% 0,01149 - 0,04706) em populações de H. armigera coletadas na safra 2014/2015. Posteriormente, foram conduzidos o monitoramento da suscetibilidade com bioensaios de doses diagnósticas (DL99) de cada inseticida em populações de H. armigera coletadas no período de 2013 a 2017. Foram observadas reduções significativas na suscetibilidade a inseticidas diamidas em populações de H. armigera no decorrer das safras agrícolas, com sobrevivências de lagartas de 0% (em 2013) até 22% (em 2017). Não foram observadas diferenças significativas na suscetibilidade a inseticidas espinosinas em populações de H. armigera no decorrer das safras agrícolas de 2013 a 2016. Contudo, foram verificadas reduções significativas na suscetibilidade das populações avaliadas na safra 2016/2017, com sobrevivência de até 20% na dose diagnóstica de spinosad. A razão de resistência da linhagem de H. armigera resistente a flubendiamide foi &asymp; 1770 vezes. Foram verificadas a presença de baixa resistência cruzada entre flubendiamide e outras diamidas (chlorantraniliprole e cyantraniliprole). Baseado nos cruzamentos recíprocos entre as linhagens suscetível e resistente a flubendiamide, o padrão de herança da resistência de H. armigera a flubendiamide é autossômico e incompletamente dominante. Retrocruzamentos da progênie dos cruzamentos recíprocos com a linhagem suscetível revelou que a resistência de H. armigera a flubendiamide é monogênica. Os resultados obtidos neste trabalho evidenciam o alto risco de evolução da resistência e a necessidade de implementação de estratégias de manejo da resistência a inseticidas diamidas e espinosinas em H. armigera no Brasil. / The management of Helicoverpa armigera (Hübner) in Brazil has been based mainly on chemical control. The use of insecticides from relatively new chemical groups, such as diamides and spinosyns, has increased to control H. armigera and other lepidopteran-pests occurring in different cropping production systems. For implementing a proactive insect resistance management, the objectives of this research were: (i) to characterize the baseline susceptibility to diamide (chlorantraniliprole, cyantraniliprole and flubendiamide) and sypnosyn (spinosad and spinetoram) insecticides in H. armigera populations from Brazil; (ii) to estimate the initial frequency of resistance allele to chlorantraniliprole and spinosad; and (iii) to characterize the inheritance of resistance of H. armigera to flubendiamide and the cross-resistance to other diamides. Initially, the baseline susceptibility to diamide and spinosyn insecticides was characterized in seven H. armigera populations collected in 2013/2014 growing season. Low variability in the susceptibility to diamide (< 5-fold) and sypinosyn (&asymp; 2-fold) insecticides was detected among H. armigera populations, based on LD50. The initial frequency of resistance allele of H. armigera to chlorantraniliprole, estimated by F2 screen method, was 0.00694 (CI95%, 0.00018 - 0.02561) in 2014 to 0.04348 (CI95%, 0.01216 - 0.09347) in 2015. To spinosad, the frequency was 0.02632 (CI95% 0.01149 - 0.04706) in H. armigera populations collected in 2014/2015. Then, insecticide susceptibility monitoring was conducted with diagnostic dose (LD99) bioassays of each insecticide in H. armigera populations collected from 2013 to 2017. A significant reduction in the susceptibility to diamide insecticides was detected throughout growing seasons, with larval survival from 0% (in 2013) up to 22% (in 2017). There were no significant differences in the susceptibility to spinosyn insecticides in H. armigera populations collected from 2013 to 2016. However, a significant reduction in the susceptibility was detected in populations from 2016/2017 growing season, with larval survival up to 20% at the diagnostic dose of spinosad. The resistance ratio of flubendiamide-resistant strain of H. armigera was &asymp; 1,770-fold. A low cross-resistance was detected between flubendiamide and other diamides (chlorantraniliprole and cyantraniliprole). Based on reciprocal crosses between susceptible and flubendiamide-resistant strains, the inheritance of H. armigera resistance to flubendiamide is autosomal and incompletely dominant. Backcrosses of the progenies from reciprocal crosses to the susceptible strain revealed that the resistance of H. armigera to flubendiamide is monogenic. The results obtained herein showed the high risk of resistance evolution and the need of implementation of resistance management strategies to diamide and spinosyn insecticides in H. armigera in Brazil.
27

The refuge concept in insect resistance management :|bits history and future application in South Africa / M. Gouws.

Gouws, Marijke January 2012 (has links)
Genetically modified (GM) crops developed for insect control express cry genes from the bacterium Bacillus thuringiensis (Bt). These genes produce target specific insecticidal proteins that protect the plant against insect pest attacks throughout the growing season. The largest threat to the continued success of these insecticidal GM crops is the potential development of target pest resistance. Models and theories suggested several possible strategies to delay the development of resistance. Of these strategies the high-dose/refuge strategy was selected as the optimal insect resistance management (IRM) option and is currently implemented throughout the world. The high-dose/refuge strategy comprises planting Bt maize plants that produce high doses of the toxin and non-Bt plants (refugia) in close proximity to one another. The theory behind this strategy is that the high dose of toxin kills nearly all the individuals of the target pest while the refuge area sustains susceptible pest individuals that survive on the crop and mate with survivors on the Bt crop. Recent reports of resistance development to Bt crops has raised questions about the refuge concept. In the cases where resistance has developed it was largely ascribed to non- compliance to the prescribed refuge requirements or non-functionality of the refuge approach. The Bt crops used throughout the world were developed in North America against the insect pests that occur there. Since there are differences in the lifecycles and behaviour of insect species targeted by Bt crops the refuge areas also needs to be specified for different target pests. For example, the currently used IRM strategies do not differentiate between polyphagous and monophagous pests and also do not take into account differences that exist in biology and behaviour of different pest species. These IRM strategies have also been developed mainly with large scale commercial farming systems in mind and do not take into account farming systems in developing countries. Current IRM strategies need to be revised and adapted for use by small-scale African farmers. / Thesis (MSc (Environmental Sciences))--North-West University, Potchefstroom Campus, 2012.
28

The refuge concept in insect resistance management :|bits history and future application in South Africa / M. Gouws.

Gouws, Marijke January 2012 (has links)
Genetically modified (GM) crops developed for insect control express cry genes from the bacterium Bacillus thuringiensis (Bt). These genes produce target specific insecticidal proteins that protect the plant against insect pest attacks throughout the growing season. The largest threat to the continued success of these insecticidal GM crops is the potential development of target pest resistance. Models and theories suggested several possible strategies to delay the development of resistance. Of these strategies the high-dose/refuge strategy was selected as the optimal insect resistance management (IRM) option and is currently implemented throughout the world. The high-dose/refuge strategy comprises planting Bt maize plants that produce high doses of the toxin and non-Bt plants (refugia) in close proximity to one another. The theory behind this strategy is that the high dose of toxin kills nearly all the individuals of the target pest while the refuge area sustains susceptible pest individuals that survive on the crop and mate with survivors on the Bt crop. Recent reports of resistance development to Bt crops has raised questions about the refuge concept. In the cases where resistance has developed it was largely ascribed to non- compliance to the prescribed refuge requirements or non-functionality of the refuge approach. The Bt crops used throughout the world were developed in North America against the insect pests that occur there. Since there are differences in the lifecycles and behaviour of insect species targeted by Bt crops the refuge areas also needs to be specified for different target pests. For example, the currently used IRM strategies do not differentiate between polyphagous and monophagous pests and also do not take into account differences that exist in biology and behaviour of different pest species. These IRM strategies have also been developed mainly with large scale commercial farming systems in mind and do not take into account farming systems in developing countries. Current IRM strategies need to be revised and adapted for use by small-scale African farmers. / Thesis (MSc (Environmental Sciences))--North-West University, Potchefstroom Campus, 2012.
29

Characterisation of Proteinase Inhibitors from Canegrubs for Possible Application to Genetically Engineer Pest-Derived Resistance into Sugarcane

Nutt, Kerry Anne January 2005 (has links)
In 1931, Mungomery stated "whitegrubs have been for years past, and still are, the worst insect problem confronting the sugar industry". This statement remains true to this day, with canegrubs costing the Australian sugar industry A$7.22 million in lost production and in use of insecticides. The development of a sugarcane cultivar with resistance to canegrub attack would be a valuable addition to the recently implemented canegrub management program. This thesis examined the possibility that natural inhibitors derived from canegrubs could be incorporated in sugarcane to reduce or prevent its destruction by canegrubs. The research described here demonstrated that canegrub haemolymph contains inhibitors with activity against commercially purified enzymes and serine proteases found in crude midgut extracts. A cDNA encoding a potential canegrub protease inhibitor (DA10 12) belonging to the Ascaris family was cloned, but it did not have activity against the major canegrub midgut proteases. This protein does, however, still have potential for modification into a serine protease inhibitor suitable for use as a novel insect resistance transgene. The possibility of using haemolymph derived inhibitors as novel antimetabolites in a canegrub management strategy based on transgenic plants was also explored. The findings suggest that proteins with properties similar to those of DA10 12 will require the presence of a signal peptide and/or codon optimisation for successful expression in sugarcane. The research outlined in this thesis is the first investigation of protease inhibitors in the haemolymph of scarab larvae, and is the first report of an Ascaris family inhibitor that does not inhibit a serine protease.
30

Resistência de genótipos de soja Glycine max (L.) a Piezodorus guildinii (Westwood)(Hemiptera: Pentatomidae)

Silva, José Paulo Gonçalves Franco da [UNESP] 27 February 2013 (has links) (PDF)
Made available in DSpace on 2014-06-11T19:28:38Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-02-27Bitstream added on 2014-06-13T18:58:03Z : No. of bitstreams: 1 silva_jpgf_me_botfca.pdf: 2329660 bytes, checksum: 9d73263f8a748ac3e9b408052e6630c7 (MD5) / Os percevejos pentatomídeos estão entre as pragas mais importantes da soja, Glycine max (L.) Merrill. Dentre esses percevejos, Piezodorus guildinii (Westwood, 1837) (Hemiptera: Pentatomidae) é uma das espécies predominantes, apresentando danos mais severos que as demais espécies. Devido aos danos à produtividade e qualidade da soja ocasionados por esse inseto, e considerando-se a carência por métodos de controle eficientes e menos agressivos ao meio-ambiente, este trabalho avaliou a possível resistência de 17 genótipos de soja, pertencentes a três grupos de maturação frente ao ataque de P. guildinii. Avaliou-se a infestação a campo, além da atratividade, preferência alimentar e biologia em laboratório (Temp.= 26  2ºC, U.R.= 65  10% e fotoperíodo=14h). Adicionalmente, parâmetros de produtividade, classificação de danos em grãos, além da quantificação de tricomas nas vagens também foram analisados, visando correlações com a infestação do inseto. Dentre os genótipos de ciclo precoce, PI-171451, PI-229358 e D75-10169 foram os menos atrativos a P. guildinii e PI-171451 e ‘IAC-17’ foram os mais produtivos. PI-229358 e PI-171451 apresentaram os menores pesos de 100 grãos; PI-171451 também apresentou a menor porcentagem de grãos danificados. Para os genótipos semiprecoces, PI-227687, IAC-74-28 e IAC-782318 foram os menos atrativos a campo; em laboratório, ‘IAC-100’ e PI-227687 mostraram esta mesma característica. PI-227687, ‘IAC-100’ e IAC-782318 mantiveram boa produtividade mesmo sob infestação, indicando antixenose e/ou tolerância. PI-227687 e IAC-782318 mostraram valores inferiores para peso de 100 grãos e para grãos danificados. IAC-100, IAC-782318 e PI-22787 são menos consumidos por P. guildinii em laboratório, indicando antixenose para alimentação. Nos materiais tardios... / Stink bugs have been described among the major pests of soybean, Glycine max (L.). Piezodorus guildinii (Westwood) (Hemiptera: Pentatomidae) is one of the predominant species, showing damage more harmful than other stink bugs. Due to it is damage on the yield and on the quality of soybean grains, and also considering the lack of control methods more effective and less harmful to the environment, this work aimed to evaluate 17 soybean genotypes, with three different phenological cycles, to P. guildinii. We evaluated the infestation in the field, and the attractiveness, feeding preference and biological parameters at laboratory (T= 26  2ºC, R.U.= 65  10% and photoperiod=14h). We also evaluated yield, content of damaged grains and number of trichomes on the pods, aiming to correlate to stink bugs infestation. Among the genotypes of early cycle, PI-171451, PI-229358 and D75-10169 were the least attractive to P. guildinii and PI-171451 e ‘IAC-17’ were the most productive. PI-229358 and PI-171451 showed the lowest weight of 100 grains; PI-171451 also had the lowest index of damaged grains. For the semi-early cycle genotypes, PI-227687, IAC-74-28 and IAC-782318 were the least attractive to insects under field conditions; ‘IAC-100’ and PI-227687 showed the same characteristic in the laboratory. PI-227687, ‘IAC-100’ and IAC-782318 maintained the yield at satisfactory levels, even when infested by stink bugs, indicating nonpreference expression. PI-227687 and IAC-782318 displayed lower means for weight of 100 grains and for damaged grains. ‘IAC-100’, IAC-782318 e PI-22787 were the least consumed by P. guildinii at laboratory, indicating feeding nonpreference as resistance mechanism. Among the late cycle genotypes, PI-274453 and PI-274454 showed the lowest infestation, with smaller... (Complete abstract click electronic access below)

Page generated in 0.0842 seconds