The characterization of DNA puff BhC4-1 expression was extended and its response to 20-hydroxyecdysone investigated in Bradysia hygida and in transgenic Drosophila carrying the BhC4-1 gene. In both organisms the activation of BhC4-1 in salivary glands occurs at the end of the larval stage coinciding with the peak in ecdysone titers which induces metamorphosis. Injections of 20-hydroxyecdysone into mid-fourth instar larvae of B. hygida show that the induction of BhC4-1 expression, as well as amplification and puff C4 expansion, are late events induced by the hormone. This late response of BhC4-1 expression was also observed in transgenic salivary glands cultivated in the presence of 20-hydroxyecdysone. In vitro studies using transgenic Drosophila indicate that both repressor and activator factors regulate the timing of BhC4-1 expression in salivary glands.
Brazil is one of the main tomato (Solanum lycopersicum) producers worldwide. Nevertheless, considerable part of the production is lost due to Bemisia tabaci (Genn.) B biotype attacks. Resistant plants can be an important method for controlling this pest in an integrated pest management. Tests for evaluating some biological aspects of B. tabaci were carried out on 18 tomato genotypes, in controlled laboratory greenhouse conditions. Thirty-day-old plants placed in plastic cages were infested with 20 whitefly pairs each, for 24 h. The development of at least 30 eggs in three leaflets per plant (repetition) was observed until adult emergence. The development period of insects grown in LA1335, PI365928 and LA722 genotypes took three days longer when compared to the ones grown in PI134418 (20.3 days). The highest mortality rate of whitefly nymphs occurred in PI365928, LA1335 and LA722 genotypes (63.8, 54.5 and 53.3%, respectively), and the smallest ones in IAC294 and IAC68F-22-2 genotypes (4.9 e 6.2%, respectively). LA1335, PI365928 and LA722 genotypes presented moderate feeding nonpreference and/or antibiosis-based resistance to B. tabaci B biotype.
Brazil is one of the main tomato producers worldwide. Nevertheless, 40 to 70% of the production is lost due to Bemisia tabaci (Gennadius) B biotype attacks. Resistant plant germplasm can be an important method for controlling this pest in an integrated pest management program. This research aimed to evaluate the no-choice ovipositional preference of B. tabaci B biotype on 18 tomato genotypes with different densities and types of trichomes testing two screening techniques and to determine the influence of trichomes on whitefly ovipositional preference. Two methods of confinement experiments were used. Leaflets detached from the upper third part of the tomato plants (first experiment) and 30-day-old plants (second experiment) were infested with whiteflies during 24 h. For the first experiment, simple linear correlation tests between the number of insects and eggs, and number of trichomes in the tomato genotypes were carried out. The first technique was better than the second one, as it was easier to carry out and the evaluation demanded less time and as well as was effective to discriminate the resistance level of the evaluated genotypes. Glandular trichomes had a negative correlation with attracted adults and number of eggs deposited, and a positive correlation with number of trapped insects. Negative correlations were observed between number of nonglandular trichomes and trapped insects, and also between total number of trichomes and attracted and trapped insects. Positive correlations were observed between number of total trichomes and eggs cm -2 and nonglandular trichomes and number of eggs. Both confinement methods efficiently discriminated whitefly oviposition among genotypes, especially the resistant ones. High levels of antixenosis for oviposition related to type IV glandular trichomes were exhibited by genotypes LA716, PI134417 and PI134418. The high level of ovipositional preference by B. tabaci for genotypes LA1963 and NAV1062 was related to a high density of type V nonglandular trichomes. Key words: Solanum lycopersicum, plant resistance, whitefly, antixenosis, trichomes Não-preferência para oviposição de Bemisia tabaci (Gennadius) biótipo B em genótipos de tomateiro em teste sem chance de escolha RESUMO: O Brasil é um dos maiores produtores mundiais de tomate, porém grande parte da produção é perdida devido ao ataque de Bemisia tabaci (Gennadius) biótipo B. Entre as táticas de controle dessa praga num manejo integrado de pragas, pode-se relacionar a resistência de plantas. Avaliou-se a preferência para oviposição de B. tabaci biótipo B por 18 genótipos de tomateiro com diferentes densidades e tipos de tricomas utilizando-se dois métodos e estudou-se a influência dos tricomas nesta preferência, utilizando-se dois métodos para os experimentos de confinamento. Folíolos seccionados do terço superior dos tomateiros (primeiro método) e plantas com 30 dias de idade (segundo método) foram infestados com moscas-brancas durante 24 h. Para o primeiro experimento, foram realizados testes de correlação l...
Com o intuito de buscar métodos alternativos de manejo e de elucidar a questão referente à ação inseticida do extrato pirolenhoso, realizou-se este estudo visando avaliar o efeito do extrato pirolenhoso obtido da queima da casca de arroz sobre parâmetros biológicos e comportamentais de S. frugiperda em milho. Foi avaliado o efeito do extrato sobre a preferência e o consumo alimentar, onde as folhas fornecidas às lagartas foram tratadas por imersão no extrato pirolenhoso a 1% (v/v), e sobre parâmetros biológicos do inseto, nesse caso, sob duas condições de aplicação: a) pulverização foliar em condições de campo (na concentração de 5% - v/v), e b) aplicação no solo em plantas mantidas em casa de vegetação, na concentração de 10% (v/v), por meio da água de irrigação. A partir dos resultados obtidos, observou-se que o extrato pirolenhoso de casca de arroz não interfere nos aspectos biológicos e comportamentais de S. frugiperda estudados, em nenhuma das formas de aplicação avaliadas, evidenciando sua ineficiência como método de controle desse inseto-praga.
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