No abstract

The Old World bollworm, Helicoverpa armigera (Hübner), was recently introduced into Brazil, where it has caused extensive damage to cotton and soybean crops. MON 87701 × MON 89788 soybean, which expresses the Bt protein Cry1Ac, was recently deployed in Brazil, providing high levels of control against H. armigera. To assess the risk of resistance to the Cry1Ac protein expressed by MON 87701 × MON 89788 soybean in Brazil, we conducted studies to evaluate the baseline susceptibility of H. armigera to Cry1Ac, in planta efficacy including the assessment of the high-dose criterion, and the initial resistance allele frequency based on an F2 screen. The mean Cry1Ac lethal concentration (LC50) ranged from 0.11 to 1.82 μg·mL−1 of diet among all H. armigera field populations collected from crop seasons 2013/14 to 2014/15, which indicated about 16.5-fold variation. MON 87701 × MON 89788 soybean exhibited a high level of efficacy against H. armigera and most likely met the high dose criterion against this target species in leaf tissue dilution bioassays up to 50 times. A total of 212 F2 family lines of H. armigera were established from field collections sampled from seven locations across Brazil and were screened for the presence of MON 87701 × MON 89788 soybean resistance alleles. None of the 212 families survived on MON 87701 × MON 89788 soybean leaf tissue (estimated allele frequency = 0.0011). The responses of H. armigera to Cry1Ac protein, high susceptibility to MON 87701 × MON 89788 soybean, and low frequency of resistance alleles across the main soybean-producing regions support the assumptions of a high-dose/refuge strategy. However, maintenance of reasonable compliance with the refuge recommendation will be essential to delay the evolution of resistance in H. armigera to MON 87701 × MON 89788 soybean in Brazil.

The pyramided genetically modified (GM) soybean [Glycine max L. (Merr.)] MON87751 × MON87708 × MON87701 × MON89788, expressing Cry1A.105, Cry2Ab2, and Cry1Ac from Bacillus thuringiensis Berliner, was approved for commercial use in Brazil. We conducted laboratory, greenhouse, and field studies to assess the efficacy of this Bt soybean against key soybean lepidopteran pests. Neonates of Anticarsia gemmatalis (Hübner) (Lepidoptera: Erebidae), Chrysodeixis includens (Walker), and Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) were exposed to Bt proteins in diet-overlay bioassays. MON87751 × MON87708 × MON87701 × MON89788 soybean and individual components were evaluated in laboratory (leaf disc), greenhouse (high artificial infestations), and in field conditions (natural infestations). Neonates of A. gemmatalis, C. includens, and H. armigera were highly susceptible to Cry1A.105 (LC50 from 0.79 to 48.22 ng/cm2), Cry2Ab2 (LC50 from 1.24 to 8.36 ng/cm2), and Cry1Ac (LC50 from 0.15 to 5.07 ng/cm2) in diet-overlay bioassays. In laboratory leaf disc bioassays and greenhouse trials, MON87751 × MON87708 × MON87701 × MON89788 soybean as well as the individual components were highly effective in controlling A. gemmatalis, C. includens, and H. armigera. Similarly, under field conditions, the pyramided genotypes expressing Cry1A.105, Cry2Ab2, and Cry1Ac were highly effective at protecting soybean against C. includens. We concluded that the individual Bt proteins expressed by GM soybean MON87751 × MON87708 × MON87701 × MON89788 killed all or nearly all the susceptible A. gemmatalis, C. includens, and H. armigera, fulfilling one important criterion for successfully delaying resistance to pyramided Bt crops.

Agriculture has sought ways to increase food production to meet global demands, intensifying dependence on natural resources. An alternative for intensive production has relied on the use of "smart" fertilizers that release nutrients in a controlled manner. Biodegradable polymers containing fertilizers has presented economic and environmental advantages when applied to the soil, as they release water and nutrients gradually to the environment without leaving residues. The objective of this study was to monitor the behavior of chitosan-clay hybrid microspheres, used as potassium nitrate soil ferti-releaser in lettuce cultivation. The experiment consisted of two treatments: (i) application of ferti-releasing chitosan-clay microspheres and (ii) use of conventional fertilization. Both treatments were monitored with TDR probes to measure electrical conductivity and soil moisture. The results indicate that both moisture and electrical conductivity are higher in soils treated with the ferti-releasing material. In addition, there was a gradual and homogenous release if compared to the conventional fertilization. The statistical analysis showed that the microspheres were efficient mainly for the controlled nitrogen release.

Compreender o comportamento da água nas plantas e no solo é uma ferramenta importante para um manejo adequado da água na agricultura. A técnica TDR pode auxiliar no monitoramento da água por ser um método preciso e não destrutivo, e ter potencial para monitorar a solução xilemática em plantas. O objetivo desse trabalho foi avaliar sondas TDR na estimativa da solução xilemática em cana-de-açúcar, correlacionando o conteúdo da solução no interior das plantas com a solução disponível no solo. O estudo foi realizado em área de segundo corte da variedade RB928064. Utilizaram-se oito plantas, e foi inserida uma sonda TDR com três hastes de 0,0016 m de diâmetro e 0,02 m de comprimento no quarto internódio e uma sonda TDR com três hastes de 0,003 m de diâmetro e 0,2 m de comprimento verticalmente no solo junto à planta. A umidade volumétrica e a condutividade elétrica das plantas e do solo foram monitoradas durante dezessete dias não consecutivos. Os resultados demonstraram que houve relação entre umidade da planta e do solo, mas não houve para a condutividade elétrica. Entretanto, para maior acurácia da técnica em plantas observa-se a necessidade de calibração com um método padrão de estimativa de solução xilemática.Palavras-chave: umidade do solo, condutividade elétrica, manejo da água. INTRODUÇÃOUm fator limitante na expansão das áreas agricultáveis é a escassez de água que limita a produtividade de plantas de interesse agronômico. O uso de técnicas de irrigação pode melhorar a eficiência e garantir precisão no aproveitamento da água pelas culturas (Chaves & Oliveira, 2004). A aplicação eficiente da água envolve, entre outros fatores, equipamentos modernos e um manejo adequado dos sistemas de irrigação. Significando uma aplicação precisa do volume de água com a frequência requerida pela planta. Para tanto, se faz necessário dispor de informações sobre as condições hídricas do solo e evapotranspiração da cultura (Delgado-Rojas, 2003).A quantidade de água absorvida pela planta pode ser determinada pela medição do fluxo da seiva xilemática, auxiliando no manejo quando submetidas a diferentes condições climáticas e hídricas do ambiente (Delgado-Rojas, 2006). Há vários métodos para estimar o consumo de água pelas plantas e a perda por transpiração, entre estes, o método direto denominado térmico (termopares) (Reis et al., 2009). Estes são aplicados diretamente em campo, sem alterar as condições microclimáticas e fisiológicas das plantas durante as aferições (Delgados-Rojas, 2003). Três métodos são mais usuais para estimar o fluxo de seiva: o método de dissipação de calor, o método do balanço de calor e o pulso de calor (Reis