Fate and effects of insect-resistant Bt crops in soil ecosystems

Icoz, I.; Stotzky, G.

doi:10.1016/j.soilbio.2007.11.002

Cited by 306 publications

(219 citation statements)

References 145 publications

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“…Although it is still debatable if Cry proteins are in fact exudated by the roots (Saxena et al, 2004;Miethling-Graff et al, 2010), its release during root growth by the sloughing off of living cells or from wounded cells is very likely (Faure et al, 2009) and thus exposure to bacteria on the root surface can be expected. Considering the small proportion of Cry proteins in the total protein contents of the root cells (maximum B3% (w/w); see Materials and methods) and the lack of direct toxic effects on soil bacteria in general (Icoz and Stotzky, 2008), shifts in the bacterial community structure triggered by 3BT are expected to be minor. Interestingly, however, Nitrosomonas and Nitrospira, two genera involved in nitrification, were in fact slightly increased in the rhizosphere of 3BT.…”

Section: Discussionmentioning

confidence: 99%

Importance of rare taxa for bacterial diversity in the rhizosphere of Bt- and conventional maize varieties

et al. 2012

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Ribosomal 16S rRNA gene pyrosequencing was used to explore whether the genetically modified (GM) Bt-maize hybrid MON 89034 × MON 88017, expressing three insecticidal recombinant Cry proteins of Bacillus thuringiensis, would alter the rhizosphere bacterial community. Fine roots of field cultivated Bt-maize and three conventional maize varieties were analyzed together with coarse roots of the Bt-maize. A total of 547 000 sequences were obtained. Library coverage was 100% at the phylum and 99.8% at the genus rank. Although cluster analyses based on relative abundances indicated no differences at higher taxonomic ranks, genera abundances pointed to variety specific differences. Genera-based clustering depended solely on the 49 most dominant genera while the remaining 461 rare genera followed a different selection. A total of 91 genera responded significantly to the different root environments. As a benefit of pyrosequencing, 79 responsive genera were identified that might have been overlooked with conventional cloning sequencing approaches owing to their rareness. There was no indication of bacterial alterations in the rhizosphere of the Bt-maize beyond differences found between conventional varieties. B. thuringiensis-like phylotypes were present at low abundance (0.1% of Bacteria) suggesting possible occurrence of natural Cry proteins in the rhizospheres. Although some genera indicated potential phytopathogenic bacteria in the rhizosphere, their abundances were not significantly different between conventional varieties and Bt-maize. With an unprecedented sensitivity this study indicates that the rhizosphere bacterial community of a GM maize did not respond abnormally to the presence of three insecticidal proteins in the root tissue.

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Section: Discussionmentioning

confidence: 99%

Importance of rare taxa for bacterial diversity in the rhizosphere of Bt- and conventional maize varieties

et al. 2012

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“…There were differences in the temperature and rainfall between the two seasons and this may also have influenced the % C, %N, C:N ratio and nematode diversity. Seasonal changes in weather conditions have been reported to affect soil communities under transgenic crops (Griffiths et al, 2007;Icoz & Stotzky, 2008). Decomposition processes are also influenced by climatic conditions.…”

Section: Discussionmentioning

confidence: 99%

“…Temperature influences decomposition due to its association with microbial activities. Cortet et al (2006) and Icoz & Stotzky (2008) showed that decomposition in Bt maize fields was influenced more by climatic factors than the Bt gene. A comparison of HART 89M and isoline has highlighted differences in various parameters that may have been due to varietal effects.…”

Section: Discussionmentioning

confidence: 99%

Nematode diversity in soil from a field trial with decomposing Bt cotton expressing Cry1Ac and Cry2Ab2 protein

Karuri

Amata

Amugune

et al. 2013

Span. j. agric. res.

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The quality of decomposing plant materials may affect the soil community structure. The aim of the study was to determine the impact of decomposing Bt cotton and its isoline on soil nematode diversity. Bt cotton (06Z604D), isoline (99M03) and HART 89M (local non-Bt cotton cultivar) were planted for two seasons in a completely randomized block design in a confined field trial at Mwea, Kenya. After harvest the plant material was incorporated into soil and the nematode diversity was determined. The presence of Bt protein was evaluated using ELISA and insect bioassays. Abundance of bacteria feeding nematodes was significantly (p < 0.05) high but to a smaller extent in the Bt cotton plots (53.7% and 52% in the first and second season respectively) than in isoline (42.8% and 45% in the first and second season respectively). Insect bioassays detected Bt protein in the Bt cotton plots during the entire decomposition period in both seasons. There were no significant differences in nematode trophic groups composition between isoline and HART 89M. The effect of Cry2Ab2 and Cry1Ac protein in decomposing Bt cotton litter on soil nematodes was minimal. The study provides a basis for future studies on the impact of genetically engineered plants on soil nematodes in Kenyan agroecosystems.

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“…Low concentrations or lack of detection have been explained as an indication of their environmental instability caused by microbial degradation, but it should be noted that detection thresholds and extraction procedures should be considered when interpreting results. This is because previous studies have demonstrated that the Bt-toxins may be adsorbed by the soil mineral or organic fraction increasing their stability and persistence (Icoz and Stotzky, 2008;Tapp andStotzky, 1995, 1998). Christoph Tebbe presented results from studies conducted to characterize the amounts of Cry1Ab (MON810) and Cry3Bb1 (MON88017) Bt-toxins released from maize in context of their agricultural use on experimental fields in Germany.…”

Section: Fate Of Bt-toxinsmentioning

confidence: 99%

The 10th International Symposium on the Biosafety of Genetically Modified Organisms (ISBGMO), Wellington, New Zealand, November 2008

Sweet¹

2009

Environ. Biosafety Res.

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INTRODUCTIONThe first generation of biotechnology crops, containing primarily single traits for insect resistance and/or herbicide tolerance, has been grown extensively for over fifteen years after evaluation in many regulatory systems, on several continents. This has been supported by multiple biosafety studies to assure an understanding of the interaction of these plants with the environment. During this time, various regulatory systems and risk assessment have been evolving as experience accrued. However, challenges continue to arise for risk assessors as manyArticle published by EDP Sciences J. Sweet new types of products, including animal products, are developed using advanced genetic engineering techniques. Governmental and private product developers have to contend with varying regulatory approaches depending upon legislative mandates between different countries and the need for refinement of assessment strategies to accommodate new types of products. Session I of the 10th International Symposium on the Biosafety of Genetically Modified Organisms (ISBGMO) continued the exploration of biosafety research and its link to risk assessment (and regulation). This paper is a synthesis of the some of the main ideas presented in Session I. Experience and biosafety researchEconomies are based either in part or in whole upon their biological resources and this dependency is projected to increase -for food, for health, for the environment and for the renewable resources that humans need to live in a sustainable, integrated manner. Ioannis Economidis considered that the use of genetic engineering is being seen more and more as one of many tools being applied to address environmental problems and opportunities that have come to the forefront of social need -from pest and disease resistance in plants and animals, to renewable energy resources, to reduction in animal pollutants and to reduction of vectors of human and animal diseases. Such a broadening range of plant products include, for example, pharmaceuticals from transgenic banana, varied oils in plants, and higher digestibility in forage plants. Martina Newell-McGloughlin indicated that the new technologies include the tools of synthetic biology, RNA interference, and applications arising from the understandings of epigenetics, transgenomics, and paramutation. Boonyanath Nathwong said that developing countries are seeing the application of genetic engineering as a means to solve problems unmanageable by traditional breeding techniques such as virus resistant papaya, chilli and tomato as well as exportable products such as colorenhanced and long-lived orchids which can contribute positively to their economies. Without taking advantage of these technologies appropriately, trade deficits continue to be intractable problems. Biosafety research on transgenic organisms is now being seen as part of the support needed to achieve the larger social policy objectives with minimal and/or manageable unwanted associated effects. To adapt to the changing scientific and product lan...

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Fate and effects of insect-resistant Bt crops in soil ecosystems

Cited by 306 publications

References 145 publications

Importance of rare taxa for bacterial diversity in the rhizosphere of Bt- and conventional maize varieties

Importance of rare taxa for bacterial diversity in the rhizosphere of Bt- and conventional maize varieties

Nematode diversity in soil from a field trial with decomposing Bt cotton expressing Cry1Ac and Cry2Ab2 protein

The 10th International Symposium on the Biosafety of Genetically Modified Organisms (ISBGMO), Wellington, New Zealand, November 2008

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