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Transgenic maize (Zea mays L., Poaceae) event TC1507, producing the Cry1F protein of Bacillus thuringiensis Berliner, has been used for management of the fall armyworm, Spodoptera frugiperda (JE Smith) (Lepidoptera: Noctuidae), in Brazil since 2009. A strain of S. frugiperda, obtained from field collections of larvae in TC1507 maize in Minas Gerais state in 2010, was selected in the laboratory for resistance to Cry1F using leaves of TC1507 maize in two selection regimes. Continuous exposure of larvae to Cry1F was more effective than exposure for 6, 8, and 10 days in the selection of resistant S. frugiperda individuals. With only four generations of laboratory selection, a strain with high levels of resistance to Cry1F was obtained, as indicated by the survival of insects reared on leaves of TC1507 maize plants and by the more than 300‐fold resistance level measured in bioassays with the purified Cry1F protein. Importantly, reciprocal crosses between control and the Cry1F‐selected strains revealed that the resistance is autosomal and incompletely recessive, and the response obtained in the backcross of the F1 generation with the resistant strain was consistent with simple monogenic inheritance. Additionally, there were no apparent fitness costs associated with resistance either for survival or larval growth on non‐Bt maize leaves. Our findings provide experimental evidence for rapid evolution of Cry1F resistance in S. frugiperda in the laboratory and further reinforce the potential of this species to evolve field resistance to the TC1507 maize as previously reported. The resistant strain isolated in this study provides an opportunity to estimate the resistance allele frequency in the field and to determine the biochemical and molecular basis of the resistance, which should provide further information to assist in the resistance management of S. frugiperda on transgenic maize producing B. thuringiensis proteins.

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RESUMO – O cultivo do sorgo granífero avança no Brasil. Todavia, existem evidências sugerindo efeito inibitório sobre a soja cultivada em sucessão. Objetivou-se investigar o efeito inibitório do cultivo de sorgo granífero (BRS 332) sobre o desempenho da soja (Glycine max (L.) Merrill) semeada em sucessão. Para isso, realizou-se um experimento de campo em blocos ao acaso em esquema de parcela subdivididas. As parcelas foram compostas pelas culturas antecessoras sorgo e milho e as subparcelas, por cinco datas de semeadura da soja após a colheita das culturas antecessoras (0, 20, 40, 60 e 80 dias após a colheita). Observou-se que o sorgo, como cultura antecessora, resultou em menores percentagens de emergência, índice de velocidade de emergência, altura de inserção de primeira vagem e número de vagens por planta de soja, apesar da produtividade de grãos não ter sido afetada. Conclui-se que o desenvolvimento vegetativo inicial da soja é afetado negativamente quando a semeadura é realizada em até 40 dias após a colheita do sorgo. Contudo, o cultivo anterior de sorgo na mesma área, comparativamente ao cultivo anterior do milho, não é capaz de afetar a produtividade da soja.Palavras-chave: Glicine max, Sorghum bicolor, sorgoleone, Zea mays. INHIBITORY EFFECT OF SORGHUM ON SOYBEAN IN SUCCESSION  ABSTRACT - The cultivation of grain sorghum is advancing in Brazil, however, there is evidence suggesting an inhibitory effect on soybeans grown in succession. The objective of this study was to investigate the inhibitory effect of grain sorghum (BRS 332) on the performance of soybeans (Glycine max (L.) Merrill) seeded in succession. For this, a field experiment was carried out in a randomized blocks design in a subdivided plot scheme. The plots were composed of the predecessor crops sorghum and maize and the subplots were five soybean sowing dates after harvesting the predecessor crops (0, 20, 40, 60 and 80 days after harvest). It was observed that sorghum as a predecessor crop resulted in lower emergence percentages, emergence speed index, first pod insertion height and number of pods per soybean plant, although grain yield was not affected. As conclusion, the initial vegetative development of soybean was negatively affected when sowing was carried out up to 40 days after sorghum harvest. However the previous cultivation of sorghum in the same area did not affect soybean productivity, compared to the previous corn crop.Keywords: Glicine max, Sorghum bicolor, sorgoleone, Zea mays.

Tebuthiuron is one of the most widely used herbicides in the sugarcane culture and its characteristic is the long persistence in soil. When used without knowing its interactions with soil attributes, it can reduce the sustainability of cropping systems and contaminate surface and groundwaters. In this research, by using a high-performance liquid chromatography, the effects of adding organic matter in a Red-Yellow Latosol were evaluated, as for the sorption and desorption of tebuthiuron. It was concluded that there is a direct relation between the sorption of tebuthiuron and the organic matter content in Red-Yellow Latosols and there is an inverse relation for desorption. The hysteresis index was lower in samples with high organic matter content.