The bacterium Bacillus thuringiensis (Bt) produces delta-endotoxins that possess toxic properties and can be used as biopesticides, as well as a source of genes for the construction of transgenic plants resistant to insects. In Brazil, the introduction of Bt soybean with insecticidal properties to the velvetbean caterpillar, the main insect pest of soybean, has been seen a promising tool in the management of these agroecosystems. However, the increase in stink bug populations in this culture, in various regions of the country, which are not susceptible to the existing genetically modified plants, requires application of chemicals that damage the environment. Little is known about the actual toxicity of Bt to Hemiptera, since these insects present sucking mouthparts, which hamper toxicity assays with artificial diets containing toxins of this bacterium. In recent studies of cytotoxicity with the gut of different hemipterans, susceptibility in the mechanism of action of delta-endotoxins has been demonstrated, which can generate promising subsidies for the control of these insect pests in soybean. This paper aims to review the studies related to the selection, application and mode of action of Bt in the biological control of the major pest of soybean, Anticarsia gemmatalis, and an analysis of advances in research on the use of Bt for control hemipterans.

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ResumoAs substâncias repelentes ou atraentes das plantas são, principalmente, de natureza terpênica e se apresentam como moléculas de baixo peso molecular e volátil. Essas substâncias, normalmente, são conhecidas como aromáticas e se denominam óleos essenciais, os quais se acumulam em todos os órgãos vegetais. Nos vegetais, os óleos essenciais desenvolvem funções relacionadas com sua volatilidade, agindo na atração de polinizadores, na proteção contra predadores, nos patógenos, na perda de água, no aumento de temperatura e também desempenhando funções ecológicas, especialmente como inibidoras de germinação. Essas características tornam as plantas que os produzem poderosas fontes de agentes biocidas, o que é largamente estudado nos agroecossistemas, principalmente no que concerne às ações bactericida, fungicida e inseticida. Os óleos essenciais têm como principais constituintes os monoterpenos, seguidos pelos sesquiterpenos, além de compostos aromáticos de baixo peso molecular. Sua função específi ca na planta ainda é desconhecida, porém se acredita que, durante o seu desenvolvimento, as plantas superiores sintetizam terpenóides essenciais para o próprio crescimento. Essas substâncias do metabolismo secundário podem agir como inibidores de germinação, proteção contra predadores, atração de polinizadores, entre outras. Entretanto, a avaliação desses compostos com fi nalidades diversas, como, por exemplo, no controle de microrganismos patogênicos de plantas cultivadas ou, ainda, como inseticida ou herbicida natural, é recente, visto que são poucos os trabalhos de pesquisa desenvolvidos e publicados nessa área. Esta revisão em artigo trata das interações dos óleos essenciais de plantas medicinais, silvestres e cultivadas com microrganismos e insetos.Palavras-chave: óleos essenciais, insetos, fungos, bactérias. AbstractThe repelling or attracting plants substances are mainly from terpenic nature and they appear as molecules with less molecular weight and volatile. Usually, these substances are known as aromatic or essential oils, which amass themselves at all herbal organs. In the herbs, essential oils develop functions related to volatility, acting to attract the pollinating, to protect against pathogens predators, in the missing of water, to rise the temperature and also making ecological functions, especially as a germination inhibitor. These features make the plants which produce these aromatics a powerful source of biocidal agents, being steadily studied in agroecosystems, principally because of the bactericidal, fungicidal, and insecticidal activities. The main components are the monoterpenes, followed by sesquiterpenes, besides aromatic compounds with low molecular weight. The specifi c function that essential oils turns out on the plant is still unknown; however, it is supposed that the higher plants synthesize terpenoids which are essential to their growth. These substances of secondary metabolism can act as germination inhibitors, protection against predators, pollinator attractors, among others. However, t...

Binding and competition among Cry1Aa, Cry1Ac, and Cry1Ba toxins were analyzed quantitatively in vitro by using (sup125)I-labeled activated toxins and brush border membrane vesicles isolated from Chilo suppressalis larval midguts. The three toxins bound specifically to the midgut brush border membrane vesicles. Direct binding experiments showed that Cry1Aa and Cry1Ba recognized a single class of binding sites with different affinities, whereas Cry1Aa recognized two classes of binding sites, one with a high affinity and a low concentration and the other with a lower affinity but higher concentration. Competition experiments showed that toxins Cry1Ac and Cry1Ba shared a binding site in the C. suppressalis midgut membranes and that this site was also the low-affinity binding site for Cry1Aa.

The endophytic bacteria belong to a larger group of microorganisms that have their life-cycle partly or entirely inside the plant and are located in intra and inter-cellular spaces or in the vascular tissue. These bacteria can be found colonizing aerial parts or roots. This review aims to analyze the colonization strategies of endophytic bacteria through interaction with plants, as well as to highlight the metabolic influence of these organisms in plant tissues, which result in physiological and biochemical changes. Depending on the different mechanisms used internally to colonize a plant, these microorganisms are called obligate, facultative, or passive endophytes. Phytostimulation, biofertilization and biological control are mechanisms that result in the development of the plant through the production of plant hormones, bioavailability of nutrients and antagonistic action to phytopathogens, respectively. The association between endophytic bacteria and plants features important benefits such as significant increases in growth, plant biomass, length of roots, dry matter production, and grain yield. Studies show that there is a great diversity of endophytic bacteria colonizing plant structures that result in several benefits to the host plant.

The fall armyworm (Spodoptera frugiperda) is one of the most important pests of maize, causing up to 20% production losses when defoliation occurs near to flowering, or even complete destruction of plants. Among the alternatives to control this pest, the use of Bacillus thuringiensis (Bt) has gained attention due to its efficiency and low impact on natural enemies. Strains Bt dendrolimus HD 37, Bt aizawai HD 68, Bt kurstaki HD 73, Bt darmstadiensis HD 146, and Bt thuringiensis 4412 were tested against second instar larvae in in vivo assays. Suspensions of Bt aizawai HD 68 and Bt thuringiensis 4412, containing 3 x 10(8) cells/ml, induced mortality of 100% and 80.4%, respectively. To test virulence, cell concentrations of 8 x 10(5) to 3 x 10(8) cells/ml of strains Bt aizawai HD 68 and Bt thuringiensis 4412 were applied on the second instar larvae: LC50 were 6.7 x 10(6) and 8.6 x 10(6) cells/ml, respectively

Os insetos constituem uma das principais causas de danos à produção agrícola no mundo. O controle de insetos tem sido realizado por meio de agroquímicos e, em muito menor escala, pelo emprego de inseticidas biológicos. As plantas transgênicas resistentes a insetos representam uma nova alternativa no combate aos insetos-praga das lavouras. A bactéria entomopatogênica Bacillus thuringiensis Berlinier (Bt) é a fonte dos genes de resistência nas chamadas plantas-Bt, produzidas comercialmente. No presente trabalho de revisão, são abordados os aspectos relacionados à bactéria Bt como fonte de genes de resistência a insetos-pragas, plantas geneticamente modificadas, vantagens do uso de plantas-Bt, bem como perspectivas dessa ferramenta biotecnológica.