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Tritrophic interactions between crucifers, aphids and hymenopteran parasitoidsKalule, Twaha January 2000 (has links)
No description available.
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Estudios del comportamiento de Sipha (Rungsia) maydis Passerini 1860 (Hemiptera: Aphidoidae), en relación con las estrategias de defensa de sus plantas hospederasSaldúa, Vilma Luciana 14 March 2014 (has links)
El trigo pan Triticum aestivum L. es uno de los cereales más extensamente cultivado en todo el mundo. En los últimos años, el uso indiscriminado de insumos externos como los pesticidas en los sistemas agrícolas, ha traído innumerables problemas ambientales y sociales, y en consecuencia, esto ha llevado a plantearse nuevos retos en la producción de los alimentos, para desarrollar estrategias adecuadas con un mejor uso de los recursos naturales. Por ello, la producción triguera en nuestro país, tiene como desafío aumentar la productividad del cultivo y mejorar aspectos tales como las resistencias a estreses bióticos y abióticos.
Dentro del complejo de las plagas asociadas al cultivo de trigo, el pulgón negro de los cereales Sipha maydis (Passerini) ha tenido una rápida expansión en nuestro territorio desde su primer registro en 2002, afectando a los cereales de invierno. El objetivo general del presente trabajo fue analizar aspectos de la biología de Sipha maydis, a fin de estudiar la interacción con las plantas hospederas de trigo y evaluar las estrategias de defensas que estas presentan contra el áfido.
Se utilizaron 47 cultivares comerciales argentinos de trigo en el presente estudio. La caracterización de los mecanismos de defensas fue realizada mediante tres ensayos biológicos (antixenosis o no preferencia; antibiosis y tolerancia), en condiciones controladas con fotoperíodo 12:12 h (luz: oscuridad), 20° C de temperatura y 70 %HR.
Se evaluó la antixenósis o no-preferencia de S. maydis mediante la prueba de la libre selección de hospedero, para ello, se contabilizó el número de áfidos encontrados por plantas luego de la infestación de 24 h. Los resultados indicaron que seis de los 47 cultivares comerciales argentinos de trigo estudiados mostraron tener antixenosis constitutiva. Sin embargo, se observó que en aquellos cultivares caracterizados por la falta de esta resistencia antixenótica, las hormonas ácido salicílico (AS) y el ácido jasmónico (AJ) indujeron y mejoraron esta resistencia.
Se determinó el mecanismo de antibiosis en los 47 cultivares contra S. maydis analizando las modificaciones de los parámetros del ciclo de vida del insecto, la duración del tiempo inmaduro (d), la fertilidad en un período igual a d (md), la fertilidad (F), la longevidad (L), el período reproductivo (Pr), la tasa de incremento poblacional (rm). Se identificaron cuatro cultivares (Biointa 3000, Biointa 2002, Baguette 10, Baguette Premiun 11), con un fuerte efecto antibiótico que impidieron que el áfido sobreviviera más allá de unos pocos días.
Se determinó el mecanismo de tolerancia evaluando el área foliar, peso fresco, peso seco y el contenido de clorofila. La mayoría de los cultivares comerciales evaluados, presentaron un nivel alto de tolerancia para todos los parámetros analizados. Trece cultivares mostraron reducciones significativas en 1 o 2 de los parámetros evaluados, este hecho las indicaría como cultivares medianamente tolerantes.
La evaluación de los costos metabólicos relacionados con los sistemas de defensas inducidas se realizó mediante aplicaciones exógenas de AS y AJ y se calcularon algunos de los componentes del rendimiento: el número de espigas por metro lineal (NEP), el número de espiguilla por espiga (NE), el número de grano por espiga (NG) y el PMG (peso de 1000 granos). Se eligieron las 16 variedades comerciales de trigo portadoras de defensas inducibles para evaluar sus costos. Se observaron múltiples respuestas a los tratamientos hormonales en los cultivares estudiados. Algunos cultivares presentaron mejores valores en NE, NG, NEP y PMG en sus testigos en comparación con las plantas inducidas. En contraste, se observó que en algunos cultivares al ser inducidos con las hormonas tuvieron mejor comportamiento que sus testigos en el NE, NG, PMG. Algunos de los cultivares argentinos probados en este ensayo poseen defensas inducibles, sin embargo la envergadura de las evaluaciones realizadas sólo han permitido una primera aproximación a la evaluación de los costos metabólicos.
Los cultivares comerciales argentinos de trigo han mostrado tener diferentes grados de resistencia a Sipha maydis. Como resultado final de esta tesis, se han podido identificar varios cultivares comerciales de trigo con resistencia antixenótica, antibiótica y tolerancia. Así como también aquellos susceptibles al áfido. La presencia de niveles significativos de resistencia, junto a otros aspectos de interés agronómico debería ser tenida en cuenta para desarrollar un programa de manejo integrado. El uso de las hormonas mediante aplicación exógena, podría llegar a ser una herramienta ventajosa para el control de los pulgones en un manejo sustentable del cultivo, no solo porque a bajas dosis y en pocas horas, se ve el efecto inductivo y el cambio del comportamiento diferencial en los cultivares frente al estrés provocado por el insecto, sino también por ser sustancias inocuas y sin toxicidad para el ambiente.
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Molecular Basis of Plant Defense Against Aphids: Role of the Arabidopsis Thaliana PAD4 and MPL1 GenesLouis, Joe 08 1900 (has links)
Myzus persicae (Sülzer), commonly known as green peach aphid (GPA), utilizes its slender stylet to penetrate the plant tissues intercellularly and consume copious amounts of photoassimilates present in the phloem sap causing extensive damage to host plants. The compatible interaction between GPA and Arabidopsis thaliana enabled us to characterize plant response to aphid infestation. Upon GPA infestation, Arabidopsis PAD4 (PHYTOALEXIN DEFICIENT4) gene modulates premature leaf senescence, which is involved in the programmed degradation of cellular components and the export of nutrients out of the senescing leaf. Senescence mechanism is utilized by plants to limit aphid growth. In addition, PAD4 provides antixenosis (deters insect settling and feeding) and antibiosis (impair aphid fecundity) against GPA and adversely impact sieve element availability to GPA. Basal expression of PAD4 contributes to antibiosis, and the GPA-induced expression of PAD4 contributes to antixenosis. Mutation in the Arabidopsis stearoyl-ACP desaturase encoding SSI2 (suppressor of SALICYLIC ACID [SA] insensitivity2) gene that results in an accelerated cell death phenotype and dwarfing, also conferred heightened antibiosis to GPA. Results of this study indicate that PAD4 is required for the ssi2-mediated enhanced antibiosis to GPA. The PAD4 protein contains conserved Ser, Asp and His residues that form the catalytic triad of many α/β fold acyl hydrolases. Arabidopsis plants expressing mutant versions of PAD4 [PAD4(S118A) and PAD4(D178A)] supported higher numbers of GPA as compared to wild type (WT) plants in no-choice tests. Furthermore, Electrical Penetration Graph (EPG) studies revealed that S118 residue in PAD4 is essential to limit GPA feeding from the sieve elements. However, the ability to deter insect settling in choice tests was not impacted by the PAD4(S118A) and PAD4(D178A) mutations, thus suggesting that PAD4s involvement in deterring insect settling and in antibiosis are determined by separate regions of PAD4. The MPL1 (MYZUS PERSICAE INDUCED LIPASE1) gene is another critical component of Arabidopsis defense against GPA. Like PAD4, MPL1 expression is induced in response to GPA infestation. However, MPL1 is required only for antibiosis and is not essential for antixenosis against GPA. EPG analysis suggests that the mpl1 mutant allele does not impact aphid feeding behavior. Since, MPL1 exhibits lipase activity, and ssi2 petiole exudates contain elevated levels of antibiosis, we propose that antibiosis to GPA requires a lipid(s), or a product thereof.
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Interactions peuplier - puceron lanigère (Phloeomyzus passerinii (Sign.)) et processus à l’origine de l’émergence et de l’expansion des pullulations / Poplar - woolly aphid (Phloeomyzus passerinii (Sign.)) interactions and processes leading to outbreak emergence and expansionPointeau, Sophie 20 December 2011 (has links)
Comprendre les processus menant à l’émergence des insectes ravageurs indigènes, impliquant les interactions entre l’insecte, sa plante-hôte et son environnement, représente un enjeu scientifique majeur. Signalées depuis les années 1990 dans les peupleraies du Sud-Ouest de la France, les pullulations du puceron lanigère du peuplier, Phloeomyzus passerinii (Signoret) (Hemiptera : Aphididae), sont en constante expansion géographique. Nous avons adopté une approche pluridisciplinaire pour éclaircir la biologie de l’insecte et ses interactions avec l’hôte ainsi que pour déterminer si les pullulations étaient liées à des conditions environnementales favorisant des populations locales ou à l'expansion de populations méridionales. Une première approche, centrée sur les interactions peuplier-puceron a montré un comportement atypique du puceron traversant les cellules du parenchyme cortical pour atteindre son site d’alimentation localisé dans ce tissu. La résistance du peuplier affecte les performances du puceron de manière multifactorielle, mettant en évidence des propriétés antibiotique et antixénotique localisées dans le parenchyme après analyses par électropénétrographie. Une seconde approche modélisant le potentiel de croissance annuel des populations en conditions optimales a révélé que le réchauffement climatique et la composition génotypique des peupleraies auraient contribué à l’émergence des pullulations. Les risques seraient accrus dans le Nord pour un réchauffement de 1 °C. Enfin, une approche génétique retraçant l’histoire évolutive des populations du puceron a révélé une diversité génétique microsatellite assez élevée, avec 28 génotypes pour 44 individus analysés. On observe une certaine structure entre les régions populicoles, sans toutefois que l’on puisse négliger l’existence d’un flux génique entre les populations dû à une dispersion à longue distance. Ce travail apporte les bases de méthodes de prévision et prévention des risques. / Understanding the processes leading to the emergence of indigenous insect pests, involving interactions between the insect, its host plant and its environment, represents a major scientific challenge. Reported since the 1990s in poplar stands of South-Western France, the outbreaks of the woolly poplar aphid, Phloeomyzus passerinii (Signoret) (Hemiptera: Aphididae), have been expanding geographically. We have adopted a multidisciplinary approach to clarify the biology of the insect and its interactions with its host, and to determine whether the outbreaks were related to environmental conditions promoting local populations or expansion of southern populations. One approach, focusing on poplar-aphid interactions has shown an atypical feeding behaviour of the aphid, crossing the cortical parenchyma cells to reach its feeding site located in this tissue. Aphids’ performances were affected by poplar resistance in many ways, which highlights antibiotic and antixenotic properties localized in the cortical parenchyma after electrical penetration graph analysis. In a second approach, a model simulating the annual growth potential of aphid populations in optimal conditions was developed. It has revealed that global warming and genotypic composition of poplar stands have contributed to the emergence of outbreaks. A warming of 1 °C may increase the risks in the North. Finally, a genetic approach drawing the evolutionary history of aphid populations shows a relatively high microsatellite genetic diversity, with 28 genotypes out of 44 individuals tested. There is some structure between poplar stand regions, but we can’t ignore gene flow between populations due to long-distance dispersal. This work has provided the basis for forecasting methods and risk prevention.
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Resistência de genótipos de milho Bt e não-Bt a Dalbulus maidis (Hemiptera : Cicadellidae) e molicutes /Faria, Rodrigo Donizeti January 2020 (has links)
Orientador: Edson Luiz Lopes Baldin / Resumo: O milho (Zea mays L.) é um dos principais cereais cultivados no mundo. O Brasil é o terceiro maior produtor deste grão ficando atrás somente da China e dos Estados Unidos da América. A cigarrinha Dalbulus maidis (DeLong & Wolcott) (Hemiptera: Cicadellidae) causa danos diretos à cultura por meio da sucção contínua de seiva, além de ser vetora de fitopatógenos como o espiroplasma Spiroplasma kunkelli Whitcomb (CSS) e o fitoplasma Candidatus Phytoplasma asteris (MBSP), molicutes responsáveis por enfezamentos nas lavouras. O uso do controle químico dessa espécie apresenta baixa eficiência por se tratar de um inseto com alto grau de dispersão. A utilização de genótipos resistentes a pragas agrícolas é uma estratégia valiosa e compatível com as demais ferramentas do manejo integrado de pragas (MIP). O presente estudo objetivou avaliar 32 genótipos de milho não-Bt e Bt sob condições de campo, visando caracterizar a expressão de antixenose e a incidência de molicutes. Foram realizados dois experimentos, sendo o primeiro na “safrinha” (2018) e o segundo na “safra de verão” (2018/2019). Para a constatação da presença do espiroplasma e do fitoplasma, foi realizada análise PCR na “safra de verão” (2018/2019). Posteriormente, avaliou-se a possível expressão de resistência por antixenose e/ou antibiose em 11 genótipos de milho previamente selecionados no ensaio conduzido a campo (Capítulo 1), sobre D. maidis em casa de vegetação. Os parâmetros biológicos avaliados foram: duração dos estádi... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Corn (Zea mays L.) is one of the main cereals grown in the world. Brazil is the third largest producer of this grain behind only China and the United States of America. The leafhopper Dalbulus maidis (DeLong & Wolcott) (Hemiptera: Cicadellidae) causes direct damage to the crop through the continuous suction of sap, in addition to being a vector of phytopathogens such as the Spiroplasma kunkelli Whitcomb (CSS) and the phytoplasma Candidatus Phytoplasma asteris (MBSP), responsible for red stunt. The use of chemical control of this species has low efficiency because it is an individual with a high degree of dispersion. The use of genotypes resistant to agricultural pests is a valuable strategy and compatible with other integrated pest management (IPM) tools. The present study aimed to evaluate 32 no-Bt and Bt corn genotypes under field conditions, aiming to characterize the expression of antixenosis and the incidence of molicutes. Two experiments were carried out, the first in the second harvest (2018) and the second in the first harvest (2018/2019). To contact the presence of spiroplasma and phytoplasma, PCR analysis was performed in the first harvest (2018/2019). Subsequently, the possible expression of resistance by antixenosis and /or antibiosis was evaluated in 11 corn genotypes previously selected in the field trial (Chapter 1), on D. maidis in a greenhouse. The biological parameters evaluated were: duration of the stages and the nymphal period, viability per instar and to... (Complete abstract click electronic access below) / Mestre
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Metodologia de pesquisa e resistência constitutiva de genótipos de algodão a Spodoptera cosmioides (Walker) e Chloridea virescens (Fabricius) (Lepidoptera : Noctuidae) /Freitas, Carlos Alessandro de January 2019 (has links)
Orientador: Arlindo Leal Boiça Júnior / Resumo: A resistência de plantas a insetos pode trazer contribuições significativas para o manejo de Chloridea virescens (Fabricius) e Spodoptera cosmioides (Walker) em algodão. Porém, ainda há poucas informações de genótipos comerciais resistentes a essas pragas e para selecioná-los é preciso, primeiramente, estabelecer uma metodologia de pesquisa confiável, melhor diferenciar para materiais resistentes e suscetíveis. Assim, neste trabalho foram avaliados potenciais fatores capazes de interferir na expressão de resistência de algodoeiro a S. cosmioides e C. virescens e, posteriormente, foi avaliada a influência de diferentes genótipos de algodoeiro sobre o comportamento de alimentação e desenvolvimento biológico de ambas as espécies para selecionar genótipos resistentes. Foi avaliada a influência dos fatores densidade larval, estrutura vegetal e idade da planta, utilizando as cultivares DeltaOpal e FMT 701. Para S. cosmioides, o uso de duas lagartas de 3º ínstar por disco foliar oriundos da parte mediana de plantas de algodoeiro em estádio de florescimento e para C. virescens uma lagarta de 3º ínstar por disco foliar de folhas da parte superior de plantas em estádio de botão floral permitiram melhor discriminação entre as cultivares quanto seus níveis de resistência. Com base nesses resultados, foi avaliada a influência de genótipos comerciais de algodão sobre o comportamento de alimentação e desenvolvimento de ambas as espécies-praga. Em relação a S. cosmioides, foram avaliados as ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Host plant resistance can contribute significantly to the management of Chloridea virescens (Fabricius) and Spodoptera cosmioides (Walker) in cotton. However, there is still little information on commercial genotypes resistant to these pests and to select them we must first establish a reliable research methodology to better distinguish between resistant and susceptible materials. In this work, we evaluated potential factors capable of interfering in the expression of resistance of cotton to S. cosmioides and C. virescens and, subsequently, the influence of different cotton cultivars on the feeding behavior and biological development of both species was evaluated, aiming select resistant cultivars. The influence of larval density, plant structure and plant phenological stages was evaluated using the DeltaOpal and FMT 701 cultivars. The use of two 3rd instar of S. cosmioides larvae per leaf disc from the middle leaves of first open flower stage and one 3rd instar larva of C. virescens per leaf disc from the upper leaves of plants at first visible floral bub stage allowed better discrimination between genotypes as to their resistance levels. Based on these results, we evaluated the influence of commercial cotton cultivars on the feeding and developmental behavior of both pest species. For S. cosmioides were evaluated the genotypes BRS 286, BRS 293, BRS 335, BRS 336, BRS 368 RF, BRS 372, DeltaOpal, FMT 701, FMT 707, FMT 709, FM 910 and FM 993. BRS 293, BRS 335 and FMT 707 cultiv... (Complete abstract click electronic access below) / Doutor
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Metodologia de pesquisa, categorias e mecanismos de resistência em milho a Diabrotica speciosa (GERMAR) e Oligonychus pratensis (BANKS) / Research methodology, categories and mechanisms of resistance in maize to Diabrotica speciosa (GERMAR) and Oligonychus pratensis (BANKS)Costa, Eduardo Neves 26 July 2016 (has links)
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Previous issue date: 2016-07-26 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / O inseto Diabrotica speciosa (Germar) e o ácaro Oligonychus pratensis (Banks) representam uma das principais pragas da cultura do milho, no Brasil e nos EUA, respectivamente. Essas pragas são controladas principalmente via aplicação de inseticidas químicos; contudo, há alternativas para tornar o manejo dessas pragas menos impactante, como o uso de plantas resistentes. Assim, esse trabalho teve como objetivo avaliar: (1) a resistência de cultivares de milho crioulo a D. speciosa; (2) a resistência de híbridos de milho resistentes à seca ao ácaro O. pratensis; (3) os mecanismos relacionados com a resistência a essas pragas; e (4) definir, através de testes de metodologia de pesquisa, a melhor forma para a condução dos ensaios. Desse modo, o presente trabalho é constituído por quatro pesquisas. Na primeira pesquisa, foi avaliada a antibiose em 19 cultivares de milho crioulo a D. speciosa, investigando se a expressão dessa categoria de resistência estava associada com algum mecanismo morfológico (lignina, celulose, fibras, e hemicelulose) ou químico (fenóis totais). No segundo trabalho, estudou-se a tolerância em seis cultivares de milho crioulo, previamente selecionados no teste de antibiose. A tolerância foi correlacionada com alguns componentes que participam do metabolismo primário vegetal, como a clorofila, os carotenoides, a glicina betaína, e a prolina. Em um terceiro experimento, foi avaliada a oviposição de D. speciosa nas seis cultivares selecionadas, discutindo os resultados quanto ao comportamento do inseto. No quarto ensaio, estudou-se a antibiose e a tolerância a O. pratensis em híbridos de milho resistentes à seca. Nessa pesquisa, foi avaliado se marcadores moleculares associados com resistência a estresses bióticos amplificariam o DNA de plantas resistente e suscetível, e se seria visualizado polimorfismos nos padrões de banda do DNA quando examinados em gel de agarose. As cultivares de milho crioulo Pérola, Fortuna e Palha Roxa manifestaram antibiose a D. speciosa, sendo isso observado no desenvolvimento e na sobrevivência (Pérola e Fortuna), e na fertilidade (Palha Roxa) do inseto. Observou-se que as cultivares resistentes exibiram as menores perdas de lignina, celulose, fibras e hemicelulose nas raízes de milho injuriadas por larvas de D. speciosa. A cultivar Azteca, que foi a mais suscetível em teste de antibiose, se destacou como a mais tolerante ao ataque da praga, além de apresentar os maiores teores de clorofilas e carotenoides. No que diz respeito à preferência para oviposição, as fêmeas de D. speciosa ovipositaram igualmente em cultivares resistentes e suscetíveis. O ácaro O. pratensis encontrou dificuldades para se desenvolver e sobreviver no híbrido de milho resistente à seca Artesian. Seis genes relacionados com resistência a estresses bióticos foram encontrados nesse híbrido, enquanto que no híbrido Droughtgard, que foi suscetível ao ácaro, nenhum daqueles genes foi observado. Os resultados obtidos neste trabalho demonstram o potencial da resistência de plantas de milho para o controle de pragas agrícolas, fornecendo informações à respeito de alguns dos mecanismos envolvidos na resistência dos materiais estudados, contribuindo, assim, para o desenvolvimento do Manejo Integrado de Pragas / The insect Diabrotica speciosa (Germar) and the mite Oligonychus pratensis (Banks) represent one of the major maize crop pests, in Brazil and in the USA, respectively. These pests are controlled primarily through the application of chemical insecticides; however, there are alternatives to make the management of these pests less impactful, as the use of resistant plants. Thus, this work aimed: (1) to determine, through testing research methodologies, the best way to conduct the assays; to evaluate (2) the resistance of maize landraces to D. speciosa and (3) the resistance of drought resistant maize hybrids to the mite O. pratensis; and lastly, (4) to reveal the mechanisms associated with the resistance to these pests. Thereby, the present work is constituted by four researches. In the first research, the antibiosis to D. speciosa was assessed in 19 maize landraces, investigating whether the expression of this resistance category was related with some morphological (lignin, cellulose, fibers, and hemicellulose) or chemical (total phenols) mechanism. In the second work, the tolerance was studied in six maize landraces previously selected in the antibiosis test. The tolerance was correlated with some compounds which participate in the primary metabolism of plants, as the chlorophyll, the carotenoids, the glycine betaine, and the proline. In a third experiment, the oviposition of D. speciosa was assessed on the six cultivars selected, discussing the results regarding the insect behavior. In the fourth assay, the antibiosis and tolerance were assessed to O. pratensis in drought resistant maize hybrids. This research aimed also to evaluate whether molecular markers associated with resistance to biotic factors would amplify the DNA of resistant and susceptible plants, and if it would be visualized polymorphisms in the banding patterns of the DNA when examined in agarose gel. The maize landraces Pérola, Fortuna, and Palha Roxa manifested antibiosis to D. speciosa, and it was observed on the development and survival (Pérola and Fortuna), and on the fertility (Palha Roxa) of the insect. The resistant cultivars exhibited the lowest losses of lignin, cellulose, fibers, and hemicellulose in the injured maize roots by D. speciosa larvae. Interestingly, the cultivar Azteca, which was the most susceptible in the antibiosis test, stood out as the most tolerant to the pest attack, besides showing the highest amounts of chlorophyll and carotenoids. With regards to the oviposition preference, the D. speciosa females laid eggs equally on the resistant and susceptible cultivars. The mite O. pratensis found difficulties for the development and survival on the Artesian drought resistant maize hybrid. Six genes associated with resistance to biotic stresses were found in this hybrid, whereas in the susceptible hybrid, Droughtgard, no one gene was noted. The results obtained in this work displays the potential of the maize plant resistance for the control of agricultural pests, providing information as to some mechanisms involved in the resistance of the materials studied, contributing, thus, for the development of the Integrated Pest Management / CNPq: 140589/2013-9 / CNPq: 140744/2016-9 / CAPES PDSE: BEX 5710/14-6
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Caracterização de resistência de genótipos de algodoeiro a Aphis gossypii Glover (Hemiptera: aphididae) / Characterization of resistance of cotton genotypes to Aphis gossypii Glover (Hemiptera: aphididae)Morando, Rafaela [UNESP] 28 August 2017 (has links)
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Previous issue date: 2017-08-28 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / O algodoeiro Gossypium spp. se destaca como uma importante fonte de recursos renováveis, produzindo a fibra de origem vegetal mais consumida pela indústria têxtil mundial. Para a maioria dos países produtores de algodão, o ataque de insetos-praga como o pulgão Aphis gossypii Glover (Hemiptera: Aphididae), é considerado um dos principais fatores de redução de produtividade na cultura. O inseto pode ocasionar danos diretos às plantas de algodão, por meio da sucção contínua de seiva, além de indiretos, devido ao favorecimento de fumagina e transmissão de vírus. O controle desse afídeo tem sido realizado principalmente através de aplicações sucessivas de inseticidas, o que têm acelerado a seleção de populações resistentes aos ingredientes ativos. Dentre as táticas alternativas ao manejo químico, o uso de cultivares resistentes se destaca como uma valiosa estratégia para o manejo integrado de pragas (MIP). O objetivo deste trabalho foi caracterizar possíveis categorias de resistência de genótipos de algodão frente ao ataque do pulgão A. gossypii, por meio de ensaios de casa de vegetação e laboratório. Inicialmente, foi realizado um screening com 78 genótipos de algodão, a partir do qual, foram selecionados 15 materiais para ensaios de capacidade de infestação e determinação do número acumulado diário de afídeos (CAD). Posteriomente, esses genótipos selecionados foram também avaliados por meio de ensaios de antixenose e de antibiose. Na última etapa, realizou-se um ensaio com EPG (Electrical Penetration Graph) utilizando-se quatro genótipos de algodão portadores de diferentes categorias de resistência, além da análise química de taninos desses materiais, visando estabelecer correlações. No ensaio de capacidade de infestação, os genótipos G. hirsutum punctatum, IAC PV010-1664 e Acala 4-42 foram os menos colonizados, indicando a ocorrência de antixenose e/ou antibiose. Com base no ensaio de antixenose, os genótipos Deltapine Smooth Leaf (7,82 afídeos) e Variedade Reba= BTK-12 (8,54 afídeos) foram significativamente menos infestados, indicando a expressão de antixenose sobre A. gossypii. No ensaio de antibiose, G. arboreum 1 apresentou as menores médias para número total de ninfas (27,11 indivíduos), ninfas por adulto/dia (1,44 indivíduos) e ninfas até os 10 dias (18,63 indivíduos), além de reduzir a fase reprodutiva (19,84 dias), a viabilidade ninfal (79,17%), a longevidade de adultos (26,68 dias) e o período de ninfa-adulto de A. gossypii (5,68 dias), sugerindo elevados níveis de resistência por antibiose e/ou antixenose. Em FM 910 o número de ninfas produzidas por dia e aos 10 dias foi reduzido, também indicando a expressão de resistência. Para o ensaio com EPG, verificou-se que afídeos confinados ao genótipo FM 910 necessitaram de maior tempo (10,94 %) até o início da fase de ingestão floemática, sugerindo a presença de fatores antixenóticos. Em Deltapine Smooth Leaf, os afídeos apresentaram maior tempo na fase de não prova e menores períodos no primeiro vaso floemático e de ingestão em E2, indicando a expressão de antixenose e/ou antibiose. A análise química revelou maior concentração de taninos nas folhas de Deltapine Smooth Leaf em relação aos demais, sugerindo que esses compostos pode ter atuado como fatores químicos de resistência, reduzindo o tempo de alimentação do afídeo nos vasos do floema desse genótipo. A resistência de G. arboreum 1 está provavelmente mais relacionada à expressão de antibiose, visto que o afídeo se alimentou nos vasos desse material de maneira similar ao observado com o genótipo suscetível FMT 707. Os resultados obtidos neste estudo podem ser explorados em programas de melhoramento genético visando o desenvolvimento de genótipos de algodoeiro resistentes a A. gossypii. / Cotton, Gossypium spp., stands out as an important source of renewable resources, producing the most consumed vegetal fiber by the world textile industry. For most cotton producing countries, the attack of pest insects, such as the aphid Aphis gossypii Glover (Hemiptera: Aphididae), is considered one of the main productivity reducing factors in the crop. This insect can cause direct damages to cotton plants through of the continuous sucking of sap as well as indirect damages by favoring sooty mold and transmitting the virus. The control of this aphid has been done mainly through successive applications of insecticides, which have accelerated the selection of populations that are resistant to the active ingredients. Among the alternative strategies of the chemical management, the utilization of resistant cultivars is considered valuable for integrated pest management (IPM). The purpose of this work was characterize possible resistance categories of cotton genotypes against an attack of the aphid A. gossypii through greenhouse and laboratory assays. Initially, a screening was carried out with 78 cotton genotypes, and 15 materials were selected for infestation ability assays and determination of the cumulative aphid-day number (CAD). Posteriorly, these selected genotypes were also evaluated by antixenosis assays and antibiosis. In the last step, an assay with EPG (Electrical Penetration Graph) was carried out using four cotton carrier genotypes from different resistance categories besides the chemical analysis of tannins of these materials to establish correlations. In the infestation ability assay, genotypes G. hirsutum punctatum, IAC PV010-1664 and Acala 4-42 were the least colonized ones, indicating the occurrence of antixenosis and/or antibiosis. Based on the antixenosis assay, genotypes Deltapine Smooth Leaf (7.82 aphids) and Variedade Reba= BTK-12 (8.54 aphids) were significantly less infested, indicating the expression of antixenose on A. gossypii. In the antibiosis assay, G. arboreum 1 showed the lowest averages for total number of nymphs (27.11 individuals), nymphs per adult/day (1.44 individuals) and nymphs at 10 days (18.63 individuals), besides reducing the reproductive periods (19.84 days), the nymphal viability (79.17%), the adult longevity (26.68 days) and the nymph-adult period of A. gossypii (5.68 days), suggesting high levels of resistance by antibiosis and/or antixenosis. In FM 910 the number of produced nymphs per day and at 10 days was decreased, which also show resistance expression. For the assay with EPG, it was verified that aphids confined to the FM 910 genotype required a longer time (10.94%) until the beginning of the phloem ingestion phase, suggesting the presence of antioxenotic factors. In Deltapine Smooth Leaf, the aphids presented longer time in the non-probing phase and shorter periods in the first phloematic vessel and E2 ingestion, indicating the expression of antixenosis and/or antibiosis. The chemical analysis presented higher concentration of tannins in Deltapine Smooth Leaf leaves in relation to the others, suggesting that these compounds may have acted as chemical resistance factors, reducing the aphid feeding time on the vessels of this genotype phloem. The resistance of G. arboreum 1 is probably more related to the expression of antibiosis, since the aphid fed on the vessels of this material similarly to the one observed in FMT 707 susceptible genotype. The results obtained in this study can be explored in breeding programs to develop A. gossypii-resistant cotton genotypes. / CNPq: 141953/2014-4
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Mechanisms of cabbage seedpod weevil, Ceutorhynchus obstrictus, resistance associated with novel germplasm derived from Sinapis alba x Brassica napusTansey, James 11 1900 (has links)
The cabbage seedpod weevil, Ceutorhynchus obstrictus (Marsham) (Coleoptera: Curculionidae), is an important pest of brassicaceous oilseed crops, especially canola (Brassica napus L. and Brassica rapa L.) in North America and Europe. Application of foliar insecticide is the only method currently employed to control C. obstrictus populations; because this approach is environmentally unsustainable, alternatives including host plant resistance have been explored.
White mustard, Sinapis alba L., is resistant to C. obstrictus and was chosen as a potential source of resistance for B. napus oilseed. Interspecific crosses of S. alba x B. napus have produced several lines that are resistant to C. obstrictus feeding and oviposition and yield fewer, lighter-weight weevil larvae that take longer to develop. I investigated potential mechanisms of this resistance, including assessing differences in visual and olfactory cues among resistant and susceptible genotypes, and antixenosis and antibiosis. Determining effects of visual cues associated with host plant resistance required investigation of weevil vision. Deployment strategies for resistant germplasm were assessed to evaluate incorporation of susceptible refugia to promote long-term durability of resistance traits.
Results reported in Chapter 2 indicate that the C. obstrictus visual system is apparently trichromatic and incorporates receptors with response maxima near 350, 450, and 550 nm. Modelling indicated that UV light alone reduced weevil responses but the interaction of yellow and UV light increased responses at a threshold reflectance level of UV. Results reported in Chapter 3 indicated that differences in yellow and UV reflectance among host plant flowers influence host selection in C. obstrictus. Results described in Chapter 4 determine differential attraction to the odours of S. alba and B. napus and among resistant and susceptible accessions. Inferences of the identities of glucosinolates found in varying amounts among susceptible and resistant genotypes suggested that 2-phenylethyl glucosinolate influenced attractiveness. Results described in Chapter 5 indicate differences in adult feeding and oviposition preferences among resistant and susceptible genotypes. Oocyte development, larval biomass and larval development time varied among weevils feeding on resistant and susceptible genotypes. Based on results of Chapter 4, 1-methoxy-3-indolylmethyl glucosinolate was implicated as contributing to antixenosis and antibiosis resistance. Results reported in Chapter 6 describe effects of mixed plots of resistant and susceptible genotypes on weevil spatial distribution and oviposition. These results are consistent with associational resistance and attributed to reduced apparency of susceptible plants in mixtures and antixenosis resistance associated with resistant germplasm. / Plant Science
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Mechanisms of cabbage seedpod weevil, Ceutorhynchus obstrictus, resistance associated with novel germplasm derived from Sinapis alba x Brassica napusTansey, James Unknown Date
No description available.
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