ABSTRACT
ABSTRACT: Genetic use restriction technologies (GURTs) were developed to preserve the intellectual property of genetically modified crops (GM) and ensure the return of investments made by industry to obtain technology delivered through seeds. The aims of this review are to discuss the GURTs and analyze their possible applications in integrated management of agricultural pests. There are two classes of GURTs: T-GURTs (trait-based GURTs), wherein the generated seed are viable, but the next generation does not express the trait of agronomic interest, and V-GURT (variety-based GURTs), in which plants produce non viable seeds. However, beyond the seed protection purpose, the GURTs could have also other application to solve agronomic problems. One of the most important is the use of GURTs as a tool to restrict gene flow of GM traits to relative weeds. In addition, it is proposed the use of this technology in integrated weed management by preventing the GMs seed germination, which produces volunteer plants that compete with the crop of interest. Also, these volunteer plants may serve as alternative hosts for insects and pathogens in between crop seasons. The GURTs could contribute to the control of undesirable agents in agricultural systems, reducing the use of pesticides and increasing crop yields.
RESUMO: As tecnologias genéticas de restrição de uso (GURTs) foram idealizadas a fim de preservar a propriedade intelectual de culturas geneticamente modificadas (GMs) e garantir o retorno dos investimentos feitos pelas empresas para a obtenção de tecnologias transmitidas via sementes. Os objetivos dessa revisão são discutir as GURTs e analisar suas possíveis aplicações no manejo integrado de pragas agrícolas. Existem duas classes de GURTs: a T-GURT (trait-based GURT), na qual as sementes produzidas são viáveis, porém as plantas da geração seguinte não expressam o caractere de interesse agronômico, e a V-GURT (variety-based GURT), na qual as plantas produzem sementes inviáveis. Contudo, além do propósito da proteção das sementes, o uso de GURTs poderia também ter outras aplicações na resolução de problemas agronômicos. Um dos mais importantes é o uso das GURTs como ferramenta para impedir o fluxo de genes de culturas transgênicas para plantas daninhas coespecificas. Além disso, propõe-se o uso dessa tecnologia no manejo integrado de plantas daninhas, por meio da prevenção da germinação de sementes GMs, que geram plantas voluntárias que competem com a cultura de interesse. Além disso, essas plantas voluntárias podem servir como hospedeiros alternativos para insetos e patógenos nos períodos de entressafra. Dessa forma, as GURTs poderiam contribuir no controle de agentes indesejáveis em sistemas agrícolas, reduzindo a utilização de agrotóxicos e aumentando a produtividade dos cultivos.
ABSTRACT
Los productos naturales son una alternativa para el control de microorganismos que ocasionan enfermedades en los cultivos. Este trabajo tuvo como objetivo evaluar diferentes solventes para la obtención de extractos crudos a partir de exudados foliares de líneas de tabaco, y el efecto in vitro de estos extractos contra dos bacterias fitopatógenas: Xanthomonas campestris (Xc) y Pectobacterium carotovorum (Pc). Se evaluaron solventes con polaridades entre 3.1 y 6.2 (diclorometano, n-butanol, acetato de etilo, metanol y etanol 90 %). El etanol 90 % se seleccionó como mejor solvente y como sustituto del diclorometano por su mayor rendimiento. Los extractos etanólicos crudos se obtuvieron a partir de exudados foliares de diez líneas de tabaco seleccionadas. La diversidad de la composición química de los extractos etanólicos se reveló por cromatografía en capa delgada. La actividad antibacteriana se evaluó por el método de difusión en agar con discos de papel de filtro y la medición del diámetro del halo de inhibición. Se observó inhibición para todos los extractos contra Xc destacándose los correspondientes a las líneas Nic 1061 "TI 1738" y Nic 1016 "Incekara" hasta 5 µg de extracto crudo seco /disco, con un mayor rendimiento para la línea Nic 1061. El extracto de la línea Nic 1015 fue el único con actividad contra Pc hasta 5 µg de extracto crudo seco por disco. Estos resultados sugieren un uso potencial de los extractos crudos de las líneas Nic 1061 y Nic 1015 "TI 1341" como un agente efectivo para la protección de cultivos contra estas bacterias.
Natural products are an alternative to control microorganisms that cause diseases in crops. This work aimed to evaluate different solvents for obtaining crude extracts from tobacco leaf exudates and to determine in vitro effect of these extracts against two phytopathogenic bacteria: Xanthomonas campestris(Xc) and Pectobacterium carotovorum(Pc). Crude extracts from ten tobacco lines using solvents with polarities between 3.1 and 6.2 (dichloromethane, n-butanol, ethyl acetate, methanol and ethanol 90%) were obtained. Ethanol 90% was selected as the best solvent for obtaining extracts from tobacco leaf exudates and as a substitute of dichloromethane due to the best yield. The chemical composition diversity of the ethanolic extracts was revealed by thin-layer chromatography. The antibacterial activity was evaluated by agar disk diffusion method recording the inhibition zones. Growth inhibition was observed for all extracts against Xc, and the better activity corresponded to the lines Nic 1061"TI 1738" and Nic 1016 "Incekara" until a minimal amount of 5 µg/ disc, with higher yield in case of the line Nic1061 . Only the extract of the line Nic 1015 was able to inhibit the growth of Pc until a minimal inhibitory concentration of 5 µg/disc. These results suggest a potential use of crude extracts from lines Nic 1061 and Nic 1015 "TI 1341" as an effective agent for the crop protection against Xc and Pc respectively.
ABSTRACT
Aims: To study the efficacy of different solvent extracts (chloroform, ethanol, methanol and hexane) of ten plants on Ralstonia solanacearum the causal organism of bacterial wilt of tomato. Place and Duration of Study: Departments of Crop Production, Soil and Environmental Management and Biological Sciences, Bowen University, Iwo, Nigeria from August 2011 to April 2012. Methodology: Ten plants namely Ocimum gratissimum, Vernonia amygdalina, Allium sativum, Zingiber officinale, Cymbopogon citratus, Azadirachta indica, Jatropha curcas, Senna obtusifolia, Senna occidentalis and Senna alata were collected from Iwo, air dried and pulverized. Chloroform, ethanol, methanol and hexane were used to extract active ingredients from the ten plants. The solvent extracts were tested against R. solanacearum the causal organism of bacterial wilt of tomato and other plants using the disc diffusion method on Mueller Hinton agar. The minimum inhibitory concentration (MIC) of the effective extracts was determined. Results: The plant extracts from chloroform were the most active and this was followed by methanol and ethanol, the lowest activity was recorded from the hexane extracts. The chloroform extracts of J. curcas had the widest zone of inhibition of 15mm followed by O. gratissimum (13mm). All the solvent extracts of A. sativum were active except the hexane extract. The means and standard error of triplicate tests were recorded. The MIC of the active extracts were studied, the MIC of the A. sativum ethanolic extract was 0.25 mg/ml while it was 0.5mg/ml for the V. amygdalina ethanol extract. The MIC of the A. sativum chloroform extract was 0.25mg/ml; J. curcas chloroform extract MIC was 0.125mg/ml, and the MIC for methanolic extract of both extracts were 0.5mg/ml and 0.25mg/ml respectively. Conclusion: The activities of the different solvent extracts are remarkable when compared with the water extracts. Hence, solvent extracts will enhance the efficacy of these phytochemicals in the management of R. solanacearum infections as opposed to water extracts.