Browsing by Subject "Genetically modified"

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    Genotypische Variation der Überdauerungsneigung von transgenem und konventionell gezüchtetem Raps und Möglichkeiten der Beeinflussung durch Bodenbearbeitung als Beitrag zur Sicherheitsforschung bei transgenen Kulturpflanzen
    (2004) Gruber, Sabine; Claupein, Wilhelm
    High losses during harvesting of oilseed rape in combination with secondary dormancy of the seeds can result in a large soil seed bank which may persist for several years. Volunteers emerging from this seed bank cannot be controlled completely, particularly when they develop in another rapeseed population. In addition to well known agricultural problems, the risk of temporal and spatial gene dispersal by persistent seeds and volunteers gets more significant. With regard to genetically modified (GM) cultivars, seed dormancy and persistence of oilseed rape volunteers have to be reconsidered. The aim of the current study was to investigate the chances for a reduction of seed persistence and gene dispersal by growing specific genotypes and by the implementation of appropriate tillage operations. Four publications describe and discuss experiments in the laboratory and the field on the aspects ?genotype? and ?soil tillage?. One central point was the characterisation of the genotypic variation of secondary dormancy and seed persistence in GM (herbicide tolerant) and conventionally bred oilseed rape. A gradual approach towards field conditions was performed by three experiments. The first experiment examined potential seed persistence by artificial induction of secondary dormancy in the laboratory. The second experiment was a burial of seeds in the soil for six months on a field. The third experiment examined persistence of seeds actually lost during harvest and exposed afterwards to different tillage operations in a field experiment. All three experiments showed a high genotypic variability in seed dormancy and persistence. In the laboratory the level of secondary dormancy of conventional cultivars was a total of 3?76% and of the GM cultivars 1?31%. The number of persistent seeds in the burial experiment was 7?90% in the conventional and 12?79% in the GM assortment. Seeds from the seed rain of the four conventionally bred cultivars in the field experiment persisted in the soil from 0?11% over six months. A significant, positive correlation was found between the laboratory results for cultivars from two crop years as well as between the results from laboratory and burial experiments. This is an indication for a genetic background of seed dormancy and persistence of oilseed rape. It has been demonstrated that a laboratory method for induction of secondary dormancy can describe differences of seed persistence in the field. This result gives a chance for screening new cultivars in the laboratory to identify desired, low persistent genotypes. The other focus of the study was the effect of various tillage treatments on seed persistence and seedling recruitment in the field. Four differently intensive tillage operations incorporated the seeds of two near-isogenic cultivars at different times and soil depths, or left the soil untilled. Winter wheat was sown as following crop in all treatments whereby no weed control was performed. The highest number of seeds generally entered the soil seed bank when seeds were incorporated into the soil by stubble tillage immediately. After six months 1?14% of the initial seed input was found again in the soil in these treatments, and in one isolated case about 28%. Delaying the stubble breaking, the soil seed bank was 0?3%. Leaving the seeds undisturbed on the soil surface until direct drilling resulted in a soil seed bank of 0?17%. Therefore, the first tillage operation after harvest of oilseed rape should be performed with some time delay to avoid large soil seed banks. Soil inversion by a mouldboard plough shifted the majority of seeds into deep soil horizons from where a successful germination was restricted. In contrast, primary tillage by a rigid tine cultivator or zero tillage mainly distributed the seeds within the upper soil layer. Thus the number of flowering volunteers in the first spring was highest in these treatments, with a maximum of one volunteer m-2. Gene dispersal from oilseed rape volunteers to other rape crops and feral relatives was possible because their flowering periods overlapped. The volunteers were able to produce viable seeds, despite high levels of damage by pests and diseases. Overall, a high genotypic variability was found for seed persistence of oilseed rape. Tillage operations, particularly the time of stubble tillage, can also influence seed persistence and the occurrence of volunteers. Combined with a thorough knowledge of the processes involved, the selection of low persistent genotypes and adequate tillage operations offer chances to limit or even to avoid undesired gene dispersal from oilseed rape volunteers, and to make gene dispersal a predictable factor.
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    Public attitudes towards genetically modified provitamin A Cassava in Brazil
    (2010) Gonzalez Rojas, María Carolina; Qaim, Matin
    Cassava is a basic staple food crop with worldwide distribution, mainly in developing countries. A fundamental source of energy for the poor, cassava grows well on marginal soils and resists pests and drought. In Latin America, Brazil is the largest cassava producer and consumer. The crop is especially important in the northeastern (NE) part of the country, where poverty and malnutrition rates are higher than in the rest of the country. However, despite the crop?s dietary importance, relatively little is known about consumer preferences, which holds true not only for Brazil but also for other developing countries. Understanding consumer preferences is crucial for technology and market development, especially in the context of provitamin A biofortification, as this entails a yellow-colored cassava root. The first article, titled ?Consumer Preferences for Cassava Characteristics in Pernambuco, Brazil?, addresses this research gap. Consumer preference for different cassava attributes are analyzed using household survey data and econometric techniques. A hedonic price model is specifically developed to estimate the values that consumers place on specific product attributes. Results show the most important characteristics for local consumers are ease of peeling, time of cooking, and texture; however, root color and size as well as market location are other relevant attributes in determining price. The second article, titled ?Consumer Acceptance of Second-Generation GM Foods: The Case of Biofortified Cassava in the Northeast of Brazil?, examines whether consumers would appreciate provitamin A biofortification and accept GM cassava. For this purpose, stated preference data, collected as part of the household survey, are used. Findings suggest that attitudes towards GM biofortified cassava are generally quite positive among local consumers. Three-quarters of all respondents in the survey said they would support the introduction of this new technology. Using contingent valuation techniques, consumers were shown to be willing to pay an average price premium of 64% for GM biofortified cassava. This is high but not unrealistic, given that vitamin A deficiency and related health problems are widespread in NE Brazil. In addition, a contingent ranking choice experiment was used to better understand the trade-offs between different cassava characteristics and estimate the partial willingness to pay (WTP) for each relevant attribute. For the provitamin A attribute alone, the average consumer is willing to pay a large premium of 160%. However, a discount is required for the color change of cassava from white to yellow (-29%), and an additional discount results from the fact that the cassava is genetically modified (-61%). These are important findings for biofortification research programs that have to make choices between conventional and GM breeding techniques. It is noted that a significantly positive WTP does not imply that GM provitamin A cassava will indeed be sold at a premium. The technology is being developed by the public sector with the aim to reduce malnutrition among the poor, so a low price should be sought to enable easy access. Hence, the WTP survey is a tool to better understand consumer attitudes rather than an approach to develop a pricing strategy for a new commercial product. The third article, titled ?Stakeholder Positions toward GM Food: The Case of Vitamin A Biofortified Cassava in Brazil?, gathers experiences from around the world and shows that stakeholder positions can crucially influence the efficiency of GM regulatory approaches and the success of new technologies. This research builds on a survey of a large range of local stakeholders. Overall, stakeholder perceptions about GM foods are relatively positive in Brazil. Statistical analysis shows that three groups of stakeholders can be distinguished: those in favor of GM crops, those against, and those that have a more or less neutral position. Representatives of local and multinational industries and those of several governmental entities belong mostly to the first group; international and national NGOs form the second group, while scientists are mostly found in the third group. Information sources and institutional/personal relationships influence individual stakeholder positions, as do socio-demographic characteristics, such as the level of education and age. An important result is also the high level of trust that stakeholders in Brazil have, in general, in the country?s research and academic sectors. Therefore, taking into account the relevance of information and the role played by the research sector, an effective system of distributing GM crop information via government agencies and/or public media is necessary to complement the knowledge of consumers so that they can make their own informed decisions.