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Earthworm populations in a northern U.S. Cornbelt soil are not affected by long-term cultivation of Bt maize expressing Cry1Ab and Cry3Bb1 proteins
Abstract
Earthworms, which play a key role in biogeochemical processes in soil ecosystems, could be negatively affected by the cultivation of transgenic Bt crops. Studies to date have found few effects of Bt maize on earthworm species. If adverse effects occur, they are likely to be chronic or sub-lethal and expressed over large spatial and temporal scales. Our objective in the present study was to investigate potential effects on earthworm populations in soil cultivated with Bt maize in a large multiple-year field study. We surveyed the earthworm populations in 0.16-ha experimental field plots of two varieties of Cry1Ab Bt maize, one variety of Cry3Bb1 Bt maize, and three non-transgenic control varieties cultivated for four years. Four earthworm species were found in our sample: Aporrectodea caliginosa, Aporrectodea trapezoides, Aporrectodea tuberculata (collectively, the A. caliginosa species complex), and Lumbricus terrestris. We found no significant differences in the biomass of juveniles and adults for all four species between Bt and non-Bt maize varieties. From this and previous studies, we conclude that the effects of Cry1Ab and Cry3Bb1 Bt maize on the A. caliginosa species complex and L. terrestris are small. Nonetheless, general conclusions about the effects of Bt maize on earthworm populations are not warranted due to the small number of species tested. In future laboratory studies, earthworm species should be selected according to their association with a Bt crop and the impact of that species to valued soil ecosystem processes.
... * Earthworms are known to burrow the soil influencing soil processes, and aid in the fragmentation of plant residues and nutrient cycling, among other important functions (Feller et al., 2003). Few field studies have been conducted to address the effects of growing Bt maize on earthworms (Lang et al., 2006;Zeilinger et al., 2010). A study in the Northern Corn Belt of the USA showed minimal effects of Bt maize cultivars with Cry1Ab and Cry3Bb1 proteins on earthworm populations of Aporrectodea caliginosa species complex and Lumbricus terrestris species (Zeilinger et al., 2010). ...
... Few field studies have been conducted to address the effects of growing Bt maize on earthworms (Lang et al., 2006;Zeilinger et al., 2010). A study in the Northern Corn Belt of the USA showed minimal effects of Bt maize cultivars with Cry1Ab and Cry3Bb1 proteins on earthworm populations of Aporrectodea caliginosa species complex and Lumbricus terrestris species (Zeilinger et al., 2010). The authors recommended that more earthworm species, associated with maize, need to be studied particularly in other parts of the world, like the temperate parts of Australia, China and South Africa, which have abundant native species. ...
... Earthworm biomass followed the same trends (data not shown), but its significance was limited because the data were only collected during the 2009/2010 season. Similarity in the number of earthworms among all the treatments was in agreement with Lang et al. (2006) and Zeilinger et al. (2010), who reported no significant effects of Bt maize cultivars on earthworm populations under field conditions, in South East Germany and northern US Corn belt, respectively. The Proandricus spp. was dominant at our site (Plisko, J.D., Natal Museum, personal communication), whereas Lang et al. (2006) studied the Lumbricidae, and the study by Zeilinger et al. (2010) was on Lumbricus and Aporrectodea species. ...
This field study investigated effects of growing Bacillus thuringiensis (Bt) maize (MON810) on local earthworms in the Central Eastern Cape, South Africa. Two Bt maize cultivars (DKC61-25B and PAN6Q-321B) and their near-isolines (DKC61-24 and PAN6777) were grown in the 2009/2010 and 2010/2011 summer seasons. Earthworms were sampled after six, nine and eighteen weeks in 2009/2010 and after six, twelve and twenty-one weeks in the 2010/2011 season. The four maize treatments had similar earthworm counts, irrespective of sampling time, in both seasons. Sampling time had no effect in the 2009/2010 season, whereas the earthworm counts at 21 weeks after planting (WAP) were lower than the other two sampling times during the 2010/2011 season. The findings suggested that, at least in the short-term, growing Bt maize does not have negative effects on the numbers of the earthworms in the Central Eastern Cape, South Africa.
... Impacts of Bt maize expressing Cry1Ab on the earthworm species L. terrestris have been studied in the laboratory and under semi-field conditions (e.g. Saxena & Strotzky, 2001b;Zwahlen et al., 2003b;Zeilinger, et al., 2010). None of the studies showed consistent effects on L. terrestris. ...
... In a field study conducted in USA over four years, Zeilinger et al. (2010) did not observe significant differences in numbers and biomass of juvenile and adult individuals of four earthworm species (Aporrectodea caliginosa, A.trapezoides, A.tuberculata (collectively the A. caliginosa complex), and L. terrestris) in the soil of Bt maize varieties expressing Cry1Ab and Cry3Bb1 proteins and non-Bt maize. However, Zeilinger et al. underline that only a small number of earthworm species that are likely to be exposed in the field have been investigated in this and previous studies. ...
... These changes could be related to the fact that exposure to pesticides influences soil bacterial diversity and the gut community composition of earthworms by reducing energy resources and activating the antioxidant systems (Chang et al., 2021) and the immediate impact of the presence of spinosad and chlorpyrifos had on some of the OTUs may be related to pesticide degradation activities of; Bacillus sp. (Zeilinger et al., 2010;Oladipo et al., 2019;Narayanan et al., 2020;Zhang et al., 2020), Sphingomonas sp. (Kumar et al., 2021), Pseudomonas sp (Kumar et al., 2021), Luteimonas sp. ...
Earthworms and microbial communities are essential non-target soil organisms that are useful to assess the collateral impact of pesticides. The present paper reports three laboratory experiments performed to investigate the effects of sub-lethal doses of two insecticides, a biologically-derived (spinosad) and a synthetic organophosphate (chlorpyrifos), on earthworm Eisenia foetida and microorganisms in organic soil. The effects were studied in terms of behaviour, reproduction, survival, and DNA damage (comet assay) in earthworms, and Next Generation Sequencing-Illumina was employed to detect the changes in the microbial community. In addition, the influence of earthworms on the degradation kinetics of insecticides and on microbial diversity was evaluated. The weights, reproductive activity and behaviour of earthworms were particularly compromised and followed a dose-dependent trend in chlorpyrifos trials, where the insecticide's degradation wasn't affected by the presence of Eisenia foetida. However, earthworms contributed to spinosad's metabolisation without significantly impacting their health. Early DNA damage was estimated in earthworms exposed to chlorpyrifos, while the impact of spinosad was significant only at the end of the toxicity test. The analysis on the microbial community indicated the buffering effect earthworms had on the bacterial communities starting from earliest sampling until the end of the trial, as well as bacterial community members' degradation response to pesticides over time.
... Transgenic crops can cause the retention of foreign gene expression products in soil through crop stubble, root exudates and pollen transmission [38][39][40][41] and may cause changes in soil composition and content near the plant rhizosphere, which in turn affect the abundance and diversity of the soil fauna, ultimately posing a potential threat to the multiple functions of soil ecosystems [42][43][44] . At present, most related studies focus on the impacts on plants and surface animals, and only some specific orders, such as Collembola [45][46][47][48] , Haplotaxida 28,29,49 and Enchytraeidae 19,20,23 . However, the overall structure and function of the soil fauna in the field are comprehensive. ...
Soil fauna play an essential role in the soil ecosystem, but they may be influenced by insecticidal Cry proteins derived from Bacillus thuringiensis (Bt) maize. In this study, a 2-year field trial was conducted to study the effects of transgenic cry1Ie maize, a type of Bt maize (Event IE09S034), on soil fauna, with the near-isogenic line non-Bt maize (Zong 31) as a control. The soil animals were collected with Macfadyen heat extractor and hand-sorting methods, respectively, and their diversity, abundance and community composition were calculated. Then, the effects of maize type, year, sampling time and soil environmental factors on the soil fauna were evaluated by repeated-measures ANOVA, redundancy analysis (RDA) and nonmetric multidimensional scaling (nMDS). Repeated-measures ANOVA showed that the diversity and abundance of the soil fauna were not affected by maize type, while they were significantly influenced by year and sampling time. Furthermore, for both the Macfadyen and hand-sorting methods, RDA indicated that soil fauna community composition was not correlated with maize type (Bt and non-Bt maize) but was significantly correlated with year, sampling time and root biomass. In addition, it was significantly related to soil pH according to the hand-sorting method. nMDS indicated that soil fauna community composition was significantly correlated with year and sampling time; however, it was not associated with maize type. In this study, we collected soil faunal samples according to the Macfadyen and hand-sorting methods and processed the obtained data with ANOVA, RDA, and nMDS in three ways, and our data indicate that transgenic cry1Ie maize (Event IE09S034) had no substantial influence on the diversity, abundance or community composition of the soil fauna.
... Bt residues can be detected in the soil (Icoz & Stotzky, 2008) and in soil-based food chains (Andow & Zwahlen, 2016) but their eventual effect is unclear. Earthworms do not seem to be adversely affected by Bt maize (Zeilinger et al., 2010), and they are important prey for ground beetles (Lövei & Sunderland, 1996). Ground beetles are a very common arthropod group in maize fields (Lövei, 1984;Lee & Albajes, 2016), and may be responsible for a substantial share of attacks on artificial caterpillars (Mansion-Vaquié et al., 2017). ...
Humankind draws important benefits from large-scale ecological processes, termed ecosystem services yet the status of several of them is declining. Reliable monitoring methods are essential for tracking the status of ecosystem services. Predation is the mainstay of natural pest control, a key ecosystem service. We used green plasticine caterpillars to monitor predation pressure, and to obtain baseline data on predator activity in transgenic Bt vs. non-Bt maize fields in Old and New World countries. Predation pressure was measured at ground and canopy levels using an identical, small-plot experimental design in four European countries (Denmark, Slovakia, Romania, Italy) and Argentina. Total predation rate in maize was 11.7%d-1 (min. 7.2%d-1 in Argentina, max. 29%d-1 in Romania). Artificial caterpillars were attacked both by invertebrates (mostly chewing insects with 42.0% of the attack marks, and ants with 7.1%, but also predatory and parasitoid wasps, spiders and slugs), and vertebrates (small mammals, 25.5%, and birds 20.2%). Total predation at ground level (15.7%d-1) was significantly higher than in maize canopies (6.0%d-1) in all countries, except Argentina. We found no significant differences between predator pressure in Bt vs. non-Bt maize plots. The artificial caterpillar method provided comparable, quantitative data on predation intensity, and proved to be suitable for monitoring natural pest control. This method usefully expands the existing toolkit by directly measuring ecological function rather than structure.
... 72 But keeping in view the results from different experimental studies in this regard, it has been evident that Bt proteins neither harm the adult or juvenile earthworm in soil nor affect its characteristics like reproduction, growth rate, abundance, biomass and mortality rate. 73 Nematodes (e.g. Caenorhabditis elegans) Millions of nematodes, commonly known as round worms, are found in the top soil layer. ...
Transgenic plants containing Bacillus thuringiensis (Bt) genes are being cultivated worldwide to express the toxic insecticidal proteins. However, the commercial utilization of Bt crops greatly enlightens the biosafety issues worldwide. Therefore assessing the risks, caused by genetically modified crops prior to their commercial cultivation is critical issue to be addressed. In agriculture biotechnology, goal of safety assessment is not just to identify the safety of genetically modified (GM) plant, rather to demonstrate its impact on ecosystem. Various experimental studies have been made worldwide from last 20 years to investigate the risks and fears associated with non-target organisms (NTO's). The NTO's include beneficial insects, natural pest controllers, rhizobacteria, growth promoting microbes, pollinators, soil dwellers, aquatic and terrestrial vertebrates, mammals and human beings. To highlight all the possible risks associated with different GM events, information has been gathered from a total of 76 articles, regarding non-target plant and soil inhabiting organisms, and summarized in the form of current review article. No significant harmful impact has been reported in any case study related to approved GM events but still critical risk assessments are needed before commercialization of these crops.
... The roots release Cry1Ab into the soil via their exudate (Icoz and Stotzky 2008b ) during the entire vegetation period, and the toxin may be taken up by plants cultivated subsequently (Icoz et al. 2009 ) . Although more studies are needed about such exudation of Cry toxins into the soil, numerous studies indicated little or no effect on soil organisms (Blackwood and Buyer 2004 ;Grif fi ths et al. 2006 ;Cortet et al. 2007 ;Icoz et al. 2008 ;US National Research Council 2010 ;Zeilinger et al. 2010 ;Tan et al. 2010 ) , while others found low but signi fi cant effects of Bt maize on microbial community structure in soil (Turrini et al. 2004 ;Castaldini et al. 2005 ;Oliveira et al. 2008 ) . In their extensive evaluation, Icoz and Stotzky ( 2008b ) concluded that the effects of Bt maize on the soil biota are transient, but possible long-term impacts cannot be excluded. ...
Crystalline (Cry) endotoxins from Bacillus thuringiensis (Bt) and related toxins are currently being used as active ingredients of bacterial insecticides and as expressed proteins in genetically modified plants. While both approaches take advantage of the specificity of Cry toxins against various insect orders, there are characteristic differences between these technologies in (i) form of application; (ii) compatibility with agrotechnologies; (iii) composition of the active ingredients; and (iv) their environmental fate. The technical advantage of Bt plants is that they eliminate labor-and energy-demanding field applications of insecticides against insect pests manageable with Cry toxins. In turn, however, Bt plants continuously produce Cry toxin during vegetation. As a result, these Bt plants do not comply with the principle of integrated pest management, as Cry toxin administration cannot be limited to the duration of the occurrence of the insect pest targeted. Bt insecticides and Bt plants may also differ in their active ingredients (bacterial protoxins and plant-expressed preactivated toxin), which in addition to pesticide registration issues, has pronounced effects on Cry toxin resistance and environmental persistence in stubble. © 2013 Springer Science+Business Media Dordrecht. All rights reserved.
... Bt product and Bt crop residues containing crystal toxins become associated with soil particles, enhancing their environmental persistence (Fu et al., 2009). Yet, there is no evidence of impact of residues from Bt corn, Bt cotton, or sprayed Bt formulations on environmental decomposers (Addison and Holmes, 1995;Liu et al., 2009;Zeilinger et al., 2010). Furthermore, multiple-year use of Bt crops had no effect on functional rhizosphere bacterial populations (Icoz et al., 2008;Hu et al., 2009). ...
Bacterial entomopathogens and/or their toxins must be ingested and enter an insect's alimentary tract, where they multiply or are activated to initiate disease. Bacterial toxins and enzymes target midgut cells, disrupt the epithelial barrier and break through to the body cavity. Bacterial proliferation in the hemocoel causes septicemia, killing the host. Most microbial insect-control products are based on Gram-positive, spore-forming bacteria in the genus Bacillus . The most successful microbial pesticide, Bacillus thuringiensis (Bt), has dominated microbial control of insect pests. Toxin genes from Bt are cloned and transformed into plants to develop transgenic Bt crops, which have revolutionized pest control. Bt crops are protected from insect attack by constitutive production of Bt toxins. Alternative entomopathogenic bacteria include Gram-positive Bacillus sphaericus and Gram-negative Serratia bacteria. Research into novel pathogens and modified toxins aims to increase the efficacy and range of microbial insect-control technologies. This chapter reviews bacterial entomopathogens and discusses their taxonomy, genetics, pathology, and implications for insect control.
... enchytraeids (Hönemann et al., 2009) or dipteran larvae (Knecht et al., 2010). Several studies have been done investigating potential effects of Bt crops on earthworms (Saxena and Stotzky, 2001b;Zwahlen et al., 2003;Liu et al., 2009;Zeilinger et al., 2010) but little research has been conducted about effects of fungicidal GE wheat on soil fauna (Romeis et al., 2003;Peter et al., 2010;Lindfeld et al., 2010) and nothing so far about effects on earthworms. ...
Since the first introduction of genetically engineered (GE) plants, one of the major concerns has been their potential effects on non-target organisms and ecosystem services. We focused in this study on the earthworm species Lumbricus terrestris as important ecosystem engineer and studied its performance when feeding on GE antifungal wheat. We compared litter consumption, weight change and mortality of individuals feeding on GE wheat with either specific resistance against powdery mildew (Blumeria graminis) or unspecific resistance against fungi via chitinase and glucanase expression with individuals feeding on non-GE wheat or other conventional crops. We did not find detrimental direct or indirect effects of GE wheat on L. terrestris and overall L. terrrestris tended to cope even better with GE wheat varieties. Concluding from our experiment the transgene products do not harm the soil key species L. terrestris and ecosystem services like decomposition, organic matter turnover and nutrient cycling are unlikely to be affected detrimentally.
... Due to their high feeding and burrowing activity (Curry and Schmidt 2007) they enhance the surface of SOM, redistribute it vertically in the soil profile (Swift et al., 1979), change the size and activity of microorganisms in soil (Brown et al. 2000; Tiunov et al. 2001), and therefore strongly modify fertility and nutrient availability in soil (Aira et al. 2003; Haynes et al. 2003). Generally, litter breakdown by earthworms and microbial mineralization are strongly related to the chemical properties of the litter (Flegel and Schrader 2000; Curry 2004 Recently, Zeilinger et al. (2010) concluded from a four-year field study that the biomass of juveniles and adults of the earthworm species Aporrectodea caliginosa, Aporrectodea trapezoides, Aporrectodea tuberculata and Lumbricus terrestris did not differ significantly between various transgenic maize varieties (Cry1Ab and Cry3Bb1 Bt maize) and non-Bt varieties. Moreover, a microcosm study of Schrader et al. (2008) revealed a significant higher decay of Cry1Ab protein in the presence of earthworms. ...
... A 9 months leaf litter bag field study conducted in Switzerland with maize MON 88017 revealed no difference in decomposer communities (including lumbricids and enchytraeids) when compared to non-Bt-maize (Hönemann et al. 2008). In a higher-tier field study conducted in the USA, Zeilinger et al. (2010) did not observe significant differences in weight of juvenile and adult earthworms (Aporrectodea caliginosa, A. trapezoides, A. tuberculata and L. terrestris; Haplotaxida: Lumbricidae) between non-Bt-maize and Bt-maize (event MON 863) varieties during 4 years of cultivation. Mollusca (molluscs) Slugs can be abundant and play an important role in the food web of maize ecosystems Transgenic Res as prey of spiders, carabids, birds and hedgehogs (Symondson et al. 2006). ...
This review paper explores whether the cultivation of the genetically modified Bt-maize transformation event MON 88017, expressing the insecticidal Cry3Bb1 protein against corn rootworms (Coleoptera: Chrysomelidae), causes adverse effects to non-target organisms (NTOs) and the ecological and anthropocentric functions they provide. Available data do not reveal adverse effects of Cry3Bb1 on various NTOs that are representative of potentially exposed taxonomic and functional groups, confirming that the insecticidal activity of the Cry3Bb1 protein is limited to species belonging to the coleopteran family of Chrysomelidae. The potential risk to non-target chrysomelid larvae ingesting maize MON 88017 pollen deposited on host plants is minimal, as their abundance in maize fields and the likelihood of encountering harmful amounts of pollen in and around maize MON 88017 fields are low. Non-target adult chrysomelids, which may occasionally feed on maize MON 88017 plants, are not expected to be affected due to the low activity of the Cry3Bb1 protein on adults. Impacts on NTOs caused by potential unintended changes in maize MON 88017 are not expected to occur, as no differences in composition, phenotypic characteristics and plant-NTO interactions were observed between maize MON 88017 and its near-isogenic line.
... These functional and community aspects cannot be investigated in laboratory studies but require field experiments. However, there are only few works published about decomposition processes and the soil community structure in GM crop fields [17,18] and none has been performed with GM wheat so far. Our field study, embedded into a unique three-year field experiment in Switzerland (www.konsortium-weizen.ch), ...
The cultivation of genetically modified (GM) plants has raised several environmental concerns. One of these concerns regards non-target soil fauna organisms, which play an important role in the decomposition of organic matter and hence are largely exposed to GM plant residues. Soil fauna may be directly affected by transgene products or indirectly by pleiotropic effects such as a modified plant metabolism. Thus, ecosystem services and functioning might be affected negatively. In a litterbag experiment in the field we analysed the decomposition process and the soil fauna community involved. Therefore, we used four experimental GM wheat varieties, two with a race-specific antifungal resistance against powdery mildew (Pm3b) and two with an unspecific antifungal resistance based on the expression of chitinase and glucanase. We compared them with two non-GM isolines and six conventional cereal varieties. To elucidate the mechanisms that cause differences in plant decomposition, structural plant components (i.e. C∶N ratio, lignin, cellulose, hemicellulose) were examined and soil properties, temperature and precipitation were monitored. The most frequent taxa extracted from decaying plant material were mites (Cryptostigmata, Gamasina and Uropodina), springtails (Isotomidae), annelids (Enchytraeidae) and Diptera (Cecidomyiidae larvae). Despite a single significant transgenic/month interaction for Cecidomyiidae larvae, which is probably random, we detected no impact of the GM wheat on the soil fauna community. However, soil fauna differences among conventional cereal varieties were more pronounced than between GM and non-GM wheat. While leaf residue decomposition in GM and non-GM wheat was similar, differences among conventional cereals were evident. Furthermore, sampling date and location were found to greatly influence soil fauna community and decomposition processes. The results give no indication of ecologically relevant adverse effects of antifungal GM wheat on the composition and the activity of the soil fauna community.
... Overall, the studies indicated no major effects against natural enemies in Bt maize fields compared with non-Bt maize fields, with the occasional exception of taxa that were dependent on Bt-susceptible pests as hosts(Eizaguirre et al. 2006; Rose and Dively 2007). Likewise, no effects were found of Cry1Ab and Cry3Bb1 maize on the diversities of macroorganisms and microorgaisms in long-term and short-term field study inUSA (Icoz et al. 2008; Priestley and Brownbirdge 2009;Zeilinger et al. 2010). A recent report from Monsanto(2010)confirms that there is a negligible impact from the cultivation of MON 810 expressing Cry1Ab on biodiversity, abundance or survival of non-target species via the analysis of 240 questionnaires from a survey of farmers cultivating MON 810 in six European countries in 2009 and through a detailed analysis of more than 30 publications. ...
Kong-Ming Wu (Corresponding author)
The application of recombinant DNA technology has resulted in many insect-resistant varieties by genetic engineering (GE). Crops expressing Cry toxins derived from Bacillus thuringiensis (Bt) have been planted worldwide, and are an effective tool for pest control. However, one ecological concern regarding the potential effects of insect-resistant GE plants on non-target organisms (NTOs) has been continually debated. In the present study, we briefly summarize the data regarding the development and commercial use of transgenic Bt varieties, elaborate on the procedure and methods for assessing the non-target effects of insect-resistant GE plants, and synthetically analyze the related research results, mostly those published between 2005 and 2010. A mass of laboratory and field studies have shown that the currently available Bt crops have no direct detrimental effects on NTOs due to their narrow spectrum of activity, and Bt crops are increasing the abundance of some beneficial insects and improving the natural control of specific pests. The use of Bt crops, such as Bt maize and Bt cotton, results in significant reductions of insecticide application and clear benefits on the environment and farmer health. Consequently, Bt crops can be a useful component of integrated pest management systems to protect the crop from targeted pests.
... In addition to insect populations, it is useful to study the impact of Bt on other parts of the ecosystem, particularly the soil as this is where Bt spores end up when washed from the plant surface, and is the destination of Bt toxins ª 2011 The Authors Plant Biotechnology Journal ª 2011 Society for Experimental Biology, Association of Applied Biologists and Blackwell Publishing Ltd, Plant Biotechnology Journal, 9, 283-300 exuded from plant roots, released from pollen grains and released from decaying or residual plant biomass ploughed into the soil. Earthworms (oligochaetes) are good indicators of general soil health and comparisons of earthworm numbers in plots containing nontransgenic maize and Bt maize expressing cry1Ab (events Bt11 and MON 810) and cry3Bb1 (event MON 863) over 4 years showed no differences in development or biomass (Zeilinger et al., 2010). More earthworms were found within the rows of maize plants than between them in all plots, perhaps because the soil is lighter and has more biological activity and therefore represents a better source of nutrients. ...
Bacillus thuringiensis (Bt) is a soil bacterium that forms spores during the stationary phase of its growth cycle. The spores contain crystals, predominantly comprising one or more Cry and/or Cyt proteins (also known as δ-endotoxins) that have potent and specific insecticidal activity. Different strains of Bt produce different types of toxin, each of which affects a narrow taxonomic group of insects. Therefore, Bt toxins have been used as topical pesticides to protect crops, and more recently the proteins have been expressed in transgenic plants to confer inherent pest resistance. Bt transgenic crops have been overwhelmingly successful and beneficial, leading to higher yields and reducing the use of chemical pesticides and fossil fuels. However, their deployment has attracted some criticism particularly with regard to the potential evolution of pest-resistant insect strains. Here, we review recent progress in the development of Bt technology and the countermeasures that have been introduced to prevent the evolution of resistant insect populations.
... When deposited on the stream bank or retained within the stream channel, transgenic detritus is available as a food resource for both terrestrial and aquatic nontarget detritivores. Detritivores (e.g., caddisflies, earthworms, isopods) are key bioindicators for examining the impacts of Bt maize detritus on nontarget organisms because of their low mobility, diversity, and functional feeding roles (7,8,(25)(26)(27)(28)(29). Despite its prevalence in the stream network, the effects of transgenic maize on nontarget organisms will depend on input rates, retention, decomposition, persistence, and concentration of Cry1Ab protein in maize detritus. ...
Widespread planting of maize throughout the agricultural Midwest may result in detritus entering adjacent stream ecosystems, and 63% of the 2009 US maize crop was genetically modified to express insecticidal Cry proteins derived from Bacillus thuringiensis. Six months after harvest, we conducted a synoptic survey of 217 stream sites in Indiana to determine the extent of maize detritus and presence of Cry1Ab protein in the stream network. We found that 86% of stream sites contained maize leaves, cobs, husks, and/or stalks in the active stream channel. We also detected Cry1Ab protein in stream-channel maize at 13% of sites and in the water column at 23% of sites. We found that 82% of stream sites were adjacent to maize fields, and Geographical Information Systems analyses indicated that 100% of sites containing Cry1Ab-positive detritus in the active stream channel had maize planted within 500 m during the previous crop year. Maize detritus likely enters streams throughout the Corn Belt; using US Department of Agriculture land cover data, we estimate that 91% of the 256,446 km of streams/rivers in Iowa, Illinois, and Indiana are located within 500 m of a maize field. Maize detritus is common in low-gradient stream channels in northwestern Indiana, and Cry1Ab proteins persist in maize leaves and can be measured in the water column even 6 mo after harvest. Hence, maize detritus, and associated Cry1Ab proteins, are widely distributed and persistent in the headwater streams of a Corn Belt landscape.
Genetically modified (GM) crops are considered a good way to reduce insecticide use and the presence of certain agricultural pests, thus improving food and environmental safety. Nevertheless, effects of GM plant residues on the soil food web are still poorly understood. Zea mays L., enriched with a gene from Bacillus thuringiensis Berliner subsp. kurstaki (Bt) as a defence against the maize borer, is widely cultivated. In this study, we explored the invertebrate food webs associated with residues of Bt and non-Bt maize, respectively represented by DKC6575, with a Cry1Ab transgene (event MON810), and its near-isogenic Tietar variety, in a five-month field experiment. C and N stable isotopes and Bayesian mixing models were used to assess trophic niche metrics and track nutrient flows from maize residues and weeds occurring in maize crops to invertebrate detritivores and predators. While there were no initial differences in the structural components of maize residues between varieties, after five months of exposure in the field, the lignin content was higher and the organic matter content was lower in non-Bt than in Bt maize. Organic matter depletion over time was associated with a decrease in primary consumer abundance and an increase in their trophic niche width in both Bt and non-Bt maize, but it was faster in the former. The abundance of primary consumers and predators was higher in non-Bt than in Bt maize, but the distribution of organisms across trophic levels differed between varieties, with prey availability being lower in non-Bt than in Bt maize. This allowed Bt-associated predators to maintain a diet based primarily on the maize food chain throughout the experimental period. In contrast, non-Bt-associated predators were more dependent on weed-feeding prey by the end of the experiment, increasing the coupling between the maize and weed energy channels in the soil food web. Some taxon-specific effects were evident. Less vagile organisms such as Diptera had a specific diet mostly related to maize regardless of variety and time, while the diets of more vagile organisms like Coleoptera and Opiliones changed the most over time. Overall, our results suggest that the attractiveness of non-Bt maize residues for invertebrate consumers is higher than the Bt variety, although the higher recalcitrant content following decomposition reduces it over time. The attractiveness also affects the movement of invertebrate predators (potentially including pest control agents) and thus nutrient flows in tri-trophic detritus-based food webs in cultivated and uncultivated plots.
The ongoing debate about the ecological effects of Bt-crops calls for thorough reviews about the impact on soil biodiversity and their ecosystem services. Transgenic Bt-crops have been genetically modified by inserting a Bacillus thuriengensis gene so the plant expresses a Cry toxin aimed for insect crop pests. Non-target soil invertebrates are particularly recognized for their contribution to plant nutrient availability and turnover of organic matter and it is therefore relevant to protect these invertebrate taxa. A number of studies have compared the population abundance and biomass of soil invertebrates in agricultural fields planted with genetically modified Bt crops and their conventional counterparts. Here, were review and analyze a selection of studies on Protista, nematodes, Collembola, mites, enchytraeids, and earthworms systematically to empower the evidence for asking the question whether population abundances and biomasses of soil invertebrates are changed by Bt crops compared to conventional crops. 6110 titles were captured, of which 38 studies passed our inclusion criteria, and a final number of 22 publications were subject to data extraction. A database with 2046 records was compiled covering 36 locations and the Bt types Cry1Ab, Cry1Ac, Cry3Bb1 and Cry3Aa. Comparative effect sizes in terms of Hedges’ g were calculated irrespectively of statistical significance of effects of the source studies. Cry effects on populations were compared across the studies in a meta-analysis employing a hierarchical Bayesian approach of weighted data according to the level of replication. The temporal development of effect sizes was modelled, thereby taking into account the variable duration of the field experiments. There was considerable variation among soil invertebrate orders, but the sample size was insufficient and the sample heterogeneity too large to draw any credible conclusions on the effect of Cry at the order level. However, across orders there was no significant effect of Cry on soil invertebrates.
A 90 day experiment was conducted in the laboratory to investigate the potential effects of transgenic Cry1Ab-expressing rice (Bacillus thuringiensis (Bt) rice: T775 and its F1 hybrid) straw return on earthworm Eisenia fetida, compared to non-Bt rice (TYHZ) straw. Juvenile E. fetida could survive, grow up, mature and reproduce offspring well in a Bt rice treated test during the whole experiment. The significantly higher relative growth rate (RGR) was found in earthworms from Bt rice treatment than from non-Bt rice treatment on the 7th day. The period of sexual maturity for earthworms from Bt rice treatments was shortened significantly, compared to non-Bt rice treatments. Adult E. fetida survived with weight loss under Bt rice treatments. On the 7th and 15th day, earthworm RGR decreased and glutathione peroxidase (GSH-PX) activity increased under Bt rice straw treatments. Significantly fewer offspring were produced by earthworms from Bt rice than non-Bt rice treatments on the 60th and 75th day. Enzyme-linked immunosorbent assay (ELISA) determined a sharp decrease of Cry1Ab in straw mixed soil along with the experimental time, regardless of juvenile or adult earthworm treatments. Cry1Ab concentration in the earthworms from the juvenile group was significantly higher than those from the adult group. Bt rice straw return had significant effects on soil nutrients, especially on the content of total and available phosphorus. In view of two bioassays, Bt rice (T775 and its F1 hybrid) straw return presented different effects on E. fetida from the juvenile (no deleterious effect) and adult (a little negative effect) groups, that were not directly related to Cry1Ab presence and nutrient differences among the three rice variety treatments.
Genetic engineering (GE) brings the revolution in crop improvement by developing the genetically modified (GM) crops having intentional and novel traits. GM crops hold the great potential to face current challenges, in term of satisficing the increasing demand of agricultural products and food security. Despite the promises they hold, safety assessment of the GM crops is inevitable for their adoption and public concerns. Intense safety research work has been done, which indicates no direct significant adverse effect either on environment or on human health. However, in spite of intense scientific research work and available information some stones still need to be unturned. A deliberate scientific effort is required to uncover many secrets such as, mutagenicity and long-term heath effect of GM crops, in order to build enough confidence for the acceptance of such type of biotechnological innovations.
The eco-toxicological effects of Bacillus thuringiensis (Bt) maize on earthworm life-history traits were widely studied and the results were controversial, while their effects on earthworm bacterial community have been rarely studied. Here, effects of two hybrids of Bt maize [5422Bt1 (event Bt11) and 5422CBCL (MON810)] straw return on Eisenia fetida bacterial community were investigated by the terminal restriction fragment length polymorphism (T-RFLP) and polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) combing with DNA sequencing, compared to near-isogenic non-Bt maize (5422). Bt maize straw return had significant effects on soil nutrients, especially for available nitrogen (N). The significant differences were shown in soil bacterial community between Bt and non-Bt maize treatments on the 75th and 90th d, which was closely correlated with soil available N, P and K rather than Cry1Ab protein. There was no statistically significant difference in the bacterial community of earthworm gut contents between Bt and non-Bt maize treatments. The significant differences in the bacterial community of earthworm casts were found among three maize varieties treatments, which were closely correlated with Cry1Ab protein and N levels. The differentiated bacterial species in earthworm casts mainly belonged to Proteobacteria, including Brevundimonas, Caulobacter, Pseudomonas, Stenotrophomonas, Methylobacterium, Asticcacaulis and Achromobacter etc., which were associated with the mineralization, metabolic process and degradation of plants residues. Therefore, Bt maize straw return caused changes in the bacterial community of E. fetida casts, which was possibly caused by the direct (Cry1Ab protein) and non-expected effects (N levels) of Bt maize straw.
Corn (Zea mays L.) grain composition is important for human and livestock nutrition, when used as seed, and for ethanol production. However, few studies have evaluated the effects of common cultural practices on corn grain composition. This study was conducted to determine whether corn grain elemental composition is affected by tillage practices (tillage or no-tillage), and whether tillage affects grain, protein, and oil yield, and removal of elements from the field in grain. The concentration of protein, oil, P, K, Ca, Mg, Mn, Fe, Zn, Cu, and B, and grain yield were determined in years 20 and 22 of long-term tillage and no-tillage treatments. Tillage treatment did not affect any grain component across both years of sampling, but Cu concentrations were greater under no-tillage in one year. Grain, oil, and protein yield was not affected by tillage treatments across years, but was greater one year under tillage and one year under no-till. The removal of P and Fe was greater under tillage in 2010, and that of Ca and Mn was greater under no-till in 2012. Removal of Cu was greater one year under tillage and one year under no-tillage. Correlation and principle components analysis suggests that there are some differences in the relationships among the grain components between tillage treatments. However, results indicate that tillage is not a dominant factor affecting corn grain composition and removals of nutrients are dominated by grain yield and not the concentration in the grain.
Non-target effects of two varieties of Bacillus thuringiensis (Bt)-maize straw (5422Bt1 [event Bt11] and 5422CBCL [MON810]) return on the Eisenia fetida were investigated by using multilevel assessments, compared to near-isogenic non-Bt-maize (5422). 5422Bt1 straw return had no deleterious effects on adult earthworms and had significantly positive effects on juveniles over three generations. Negative, no, and positive effects on adults treated with 5422CBCL straw were observed in the 1st, 2nd and 3rd generation, respectively. Negative and positive effects were observed on juveniles produced from the 1st- and 2nd-generation adults treated with 5422CBCL straw, respectively. Glutathione peroxidase activity of earthworms from Bt-maize treatments was significantly higher than that of control on the 90th d. Translationally controlled tumour protein (TCTP) and superoxide dismutase (SOD) genes were down-regulated, while annetocin (ANN) expression was up-regulated in 5422Bt1 treatments. TCTP and SOD genes were up-regulated, while ANN and heat shock protein 70 were down-regulated in E. fetida from 5422CBCL treatments. Enzyme-linked immunosorbent assay revealed that Cry1Ab released from 5422Bt1 and 5422CBCL straw degraded rapidly on the 15th and 30th d and had a slow decline in the rest testing time. Cry1Ab concentrations in the soil, casts and guts of earthworm significantly decreased over the course of the experiment. This study was the first to evaluate generational effects of Bt-maize straw return on earthworms under laboratory conditions. The responses of enzymes activity and genes expression may contribute to better understand above different effects of Bt-maize straw return on earthworms from the 1st generation.
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There is an on-going debate on the environmental effects of genetically modified crops to which this paper aims to contribute. First, data on environmental impacts of genetically modified (GM) and conventional crops are collected from peer-reviewed journals, and secondly an analysis is conducted in order to examine which crop type is less harmful for the environment. Published data on environmental impacts are measured using an array of indicators, and their analysis requires their normalisation and aggregation. Taking advantage of composite indicators literature, this paper builds composite indicators to measure the impact of GM and conventional crops in three dimensions: (1) non-target key species richness, (2) pesticide use, and (3) aggregated environmental impact. The comparison between the three composite indicators for both crop types allows us to establish not only a ranking to elucidate which crop is more convenient for the environment but the probability that one crop type outperforms the other from an environmental perspective. Results show that GM crops tend to cause lower environmental impacts than conventional crops for the analysed indicators.
A healthy soil ecosystem is essential for nutrient cycling and energy conversion, and the impact of exogenous genes from genetically modified crops had aroused wide concerns. Phytase transgenic corn (i. e., the inbred line BVLA430101) was issued a bio-safety certificate on 27 September 2009 in China, which could improve the efficiency of feed utilization, reduce environmental pollution caused by animal manure. In this study, the abundance of trophic groups, community structure and ecological indices of soil nematodes were studied over the growing cycle of phytase transgenic corn (ab. transgenic corn) and control conventional parental corn (ab. control corn) in the field. Totally 29 and 26 nematode genera were isolated from transgenic corn and control corn fields, respectively. The abundances of bacterivores and omnivores-predators, the total number of soil nematodes, and the Shannon index (H) were significantly greater under transgenic corn than under control corn, while the opposite trend was found for the relative abundance of herbivores and the maturity index (Sigma MI) of soil nematodes. Repeated-measures analysis of variance (ANOVA) did not detect any significant effects of transgenic corn on the composition and abundance of nematode trophic groups and ecological indices of soil nematodes. Furthermore, the Student-T test showed that the abundances of bacterivores and omnivores-predators and the total number of soil nematodes during the milk-ripe stage were significant higher in the transgenic corn field than in the control corn field. The effects of transgenic corn planting on soil nematodes might be related to the increase in the nitrogen content of field soil under transgenic corn compared to control corn.
Metabolic engineering in plants can be used to increase the abundance of specific valuable metabolites, but single-point interventions generally do not improve the yields of target metabolites unless that product is immediately downstream of the intervention point and there is a plentiful supply of precursors. In many cases, an intervention is necessary at an early bottleneck, sometimes the first committed step in the pathway, but is often only successful in shifting the bottleneck downstream, sometimes also causing the accumulation of an undesirable metabolic intermediate. Occasionally it has been possible to induce multiple genes in a pathway by controlling the expression of a key regulator, such as a transcription factor, but this strategy is only possible if such master regulators exist and can be identified. A more robust approach is the simultaneous expression of multiple genes in the pathway, preferably representing every critical enzymatic step, therefore removing all bottlenecks and ensuring completely unrestricted metabolic flux. This approach requires the transfer of multiple enzyme-encoding genes to the recipient plant, which is achieved most efficiently if all genes are transferred at the same time. Here we review the state of the art in multigene transformation as applied to metabolic engineering in plants, highlighting some of the most significant recent advances in the field.
Genetically modified (GM) rice expressing Bt toxins is at the edge of commercial release in China. However, little information is available concerning the impact of Bt rice on aquatic organisms which are abundant in paddy field. A two-year study was conducted to assess the effects of two GM rice lines expressing a fusion protein Cry1Ab/1Ac (Bt rice) on three groups of zooplankton, rotifers, cladocerans and copepods in field conditions. Multi-factor ANOVA revealed that the population densities of rotifers, cladocerans and copepods in paddy field varied significantly between years and rice developmental stages, but did not differ significantly between Bt and non-Bt rice treatments. In all the field investigations, only one significant difference was found on copepods in the tillering stage of 2009, but the difference was not related to the presence of the Cry toxin. Under open-air conditions, we simulated the farming practice of straw mulch, using Bt rice straw as a food source for the water flea Daphnia hyalina. After one and two months of culture, the density of D. hyalina did not differ between Bt rice treatments and non-Bt rice treatments. A laboratory experiment found that purified Bt toxins Cry1Ab and Cry1Ac had no toxic effect on D. hyalina even in the treatment in which the Bt toxin concentration was as high as 2500ng/ml. Those above results indicate that the two Bt rice lines have no negative effect on the three groups of zooplankton. However, further studies are needed to compare the effects of Bt rice and non-Bt rice on the paddy zooplankton community in the context of integrated pest management which includes the use of pesticides.
Ultraviolet (UV) radiation leads to photooxidation in various organisms. Our previous study demonstrated that ultraviolet B (UV-B) radiation is lethal for particular species of earthworms, but the mechanisms responsible for the lethality are unclear. In our current study, we investigated that ultraviolet light causes photooxidative damage and reduces antioxidant responses in the earthworm Amynthas gracilis. Intact earthworms and skin/muscle tissue extracts were exposed to UV-B radiation for in vivo and in vitro studies. Both in vitro and in vivo results showed that the products of photooxidative damage, MDA and H(2)O(2), increased after UV-B exposure. Glutathione peroxidase (GPx) and catalase were inhibited immediately after exposure to high doses (3000J/m(2)) of UV-B radiation in vivo. Catalase activity was increased following a low UV-B dose (500J/m(2)) in vivo, but decreased in response to all dosage levels in vitro. These data indicate that a relationship exists between UV-B induced damage and photooxidation and also that catalase and GPx act as important antioxidants to prevent photooxidation. According to these data, A. gracilis exhibits high sensitivity to environmental levels of UV-B. Therefore, A. gracilis represents a sensitive and cost-effective model organism for investigations of UV-radiation damage and environmental UV stress.
Bacillus thuringiensis (Bt) proteins released from Bt corn can enter soil ecosystem via returning straw into field, root exudation, and pollen fluttering-down. In this study, the straws of Bt corn and its near-isogenic non-Bt line were added into soil with an application rate of 5% and 7.5% to breed Eisenia fetida, and the total protein content and the activities of acetylcholine esterase (AchE), glutathione peroxidase (GSH-PX), catalase (CAT), and superoxide dismutase (SOD) in E. fetida were determined after 7 and 14 days. Under the same application rate of the straws, the total protein content and GSH-PX activity of E. fetida decreased while the AchE, CAT, and SOD activities increased on the 14th day, compared with those on the 7th day. The Bt corn straw increased the SOD activity and decreased the AchE and GSH-PX activities, but had less effects on the total protein content and CAT activity, compared with non-Bt corn straw. All the results suggested that Bt corn straw had no inhibitory effect on E. fetida total protein but could inhibit the AchE and GSH-PX activities, and could not induce CAT activity but induce SOD activity within a short time.
Earthworms Eisenia fetida, bred in substances with stover of two genetically-engineered Bacillus thuringiensis (Bt) corns (5422Bt1 (Event Bt11) and 5422CBCL (MON810)) expressing Cry1Ab and their near-isogenic non-Bt corn (5422), were used to investigate the non-target effects of Bt corn on soil-dwelling organisms. Cry1Ab concentrations in substances, casts and guts of E. fetida were also investigated by Enzyme-linked immunosorbent assay (ELISA). More than 90% individuals of E. fetida survived over a period of 30 d, irrespective of whether they received Bt corn or non-Bt corn. Compared to 5422 treatments, significantly higher relative growth rate and more number of new offspring and cocoons of E. fetida were found in 5422Bt1 and 5422CBCL treatments. These results were unlikely to be directly caused by Cry1Ab released from Bt corns but rather by differences in other factors of plants such as plant components (soluble sugar, total organic carbon, total protein and available phosphorus of Bt corns were more than 5422). ELISA results indicated immunoreactive Cry1Ab was detectable in substances, and the casts, guts of E. fetida from Bt corns treatments, of which the highest levels were detected in substances under the corresponding experimental conditions. With the increase of treated time, a strong decline was observed in Cry1Ab from substances and casts of E. fetida, whereas Cry1Ab in guts of E. fetida from 5422Bt1 treatments gradually increased and that from 5422CBCL treatments increased between 14 and 30 d. Therefore, the presence of Cry1Ab in E. fetida had no deleterious effects on their growth and reproduction.
The potential impact of GM crops on biodiversity has been a topic of interest both in general as well as specifically in the context of the Convention on Biological Diversity. Agricultural biodiversity has been defined at levels from genes to ecosystems that are involved or impacted by agricultural production (www.cbd.int/agro/whatis.shtml). After fifteen years of commercial cultivation, a substantial body of literature now exists addressing the potential impacts of GM crops on the environment. This review takes a biodiversity lens to this literature, considering the impacts at three levels: the crop, farm and landscape scales. Within that framework, this review covers potential impacts of the introduction of genetically engineered crops on: crop diversity, biodiversity of wild relatives, non-target soil organisms, weeds, land use, non-target above-ground organisms, and area-wide pest suppression. The emphasis of the review is peer-reviewed literature that presents direct measures of impacts on biodiversity. In addition, possible impacts of changes in management practises such as tillage and pesticide use are also discussed to complement the literature on direct measures. The focus of the review is on technologies that have been commercialized somewhere in the world, while results may emanate from non-adopting countries and regions. Overall, the review finds that currently commercialized GM crops have reduced the impacts of agriculture on biodiversity, through enhanced adoption of conservation tillage practices, reduction of insecticide use and use of more environmentally benign herbicides and increasing yields to alleviate pressure to convert additional land into agricultural use.
With the large scale cultivation of transgenic crops expressing Bacillus thuringiensis (Bt) insecticidal crystal proteins in the world, the problem of environmental safety caused by these Bt crops has received extensive attention. These insecticidal crystal proteins can be released into the soil continuously in the growing period of Bt plants. If their accumulation of the insecticidal crystal proteins exceeds consumption by insect larvae and degradation by the environmental factors, these insecticidal crystal proteins could constitute a hazard to non-target insects and soil microbiota. There are three main ways to release insecticidal crystal proteins into soil for Bt plants: root exudates, pollen falling, and crop reside returning. The Bt insecticidal crystal proteins released into soil can be adsorbed rapidly by active soil particles and the absorption equilibrium attained within 1-3 h. The adsorption protects Bt insecticidal crystal proteins against soil microbial degradation or enzyme degradation, which leads to remarkable prolong of the persistence of insecticidal activity. The change of soil microorganism species is an important index for evaluating the effect of Bt plants on soil ecology. The research showed that these insecticidal crystal proteins released by the Bt plant root exudates or Bt organism had no toxicity to the soil earthworms, nematodes, protozoa, bacteria and fungi; however, it could reduce the mycelium length of the arbuscular mycorrhizal fungi (AMF) and restrain AMF to form invasion unit. The influencing degree of Bt protein on soil enzyme activity varied with the releasing modes or growth period of Bt crops. Bt Cry1Ab protein can be taken up from soil by parts of following crops; however, different results were obtained with different commercial kits. To better understand the soil ecological evaluation about the insecticidal crystal proteins released from transgenic Bt crops, this review provides a comprehensive overview about the release, adsorption and residue of Bt insecticidal crystal proteins in soil, as well as their effects on soil protozoa, soil microorganism, soil enzyme activity and following crops.
Many international forums have identified the need for comprehensive, scientific methods for the pre-release testing and post-release monitoring of transgenic plants to ensure their environmental safety and sustainable use. In response to this requirement, the International Project on GMO Environmental Risk Assessment Methodologies develops biosafety testing methodologies in support of risk assessment for transgenic plants. This second volume focuses on transgenic cotton that is resistant to insect pests in Brazil, and addresses both environmental and agricultural impacts. It draws out a general risk assessment concept and demonstrates the need for case-by-case analysis. This book makes a significant contribution to this field and will interest readers in crop science, biotechnology, ecology, pest management and policy analysis, with a focus on the needs of developing countries.
This chapter concentrates on the potential effects of transgenic cotton on the soil ecosystem of three major cotton growing areas in Vietnam: the coastal lowlands region, the central highlands (eastern and western Truong Son Mountain Range) and the south-eastern region. Soils in these three regions are very different, so it will be necessary to assess the effects of transgenic cotton on typical soils from all three regions. The soils in the south-eastern region are Luvisols, Andosols and Acrisols. In the central highlands, the soils are mainly Luvisols, Rhodic Ferrasols and Haplic Acrisols. The soils in the coastal lowlands region are mainly delta soils, consolidated occasionally by grey light soils.
Nontarget risk assessment for transgenic crops should be case specific, depending on the plant, the transgene, and the intended release environment. We propose an ecological risk-assessment model that preserves the strengths and avoids the deficiencies of two other commonly used models, the ecotoxicology and nonindigenous-species models. In this model, locally occurring nontarget species are classified into groups according to their ecological function. Within each group, ecological criteria are used to select the species that are most likely to be affected by the transgenic crop. Initial experimental assessments are conducted in the laboratory and consist of two kinds of test: toxicity tests using purified transgene product, and whole-plant tests using intact transgenic plants. For nontarget natural enemy species, it will also be important to evaluate both direct bitrophic impacts and indirect tritrophic impacts.
Transgenic Bt crops produce insecticidal Cry proteins that are released to soil in plant residues, root exudates, and pollen and that may affect soil microorganisms. As a continuation of studies in the laboratory and a plant-growth room, a field study was conducted at the Rosemount Experiment Station of the University of Minnesota. Three Bt corn varieties that express the Cry1Ab protein, which is toxic to the European corn borer (Ostrinianubilalis Hubner), and one Btcorn variety that expresses the Cry3Bb1 protein, which is toxic to the corn rootworm complex (Diabrotica spp.), and their near-isogenic non-Bt varieties were evaluated for their effects on microbial diversity by classical dilution plating and molecular (polymerase chain reaction-denaturing gradient gel electrophoresis) techniques and for the activities of some enzymes (arylsulfatases, acid and alkaline phosphatases, dehydrogenases, and proteases) involved in the degradation of plant biomass. After 4 consecutive years of corn cultivation (2003-2006), there were, in general, no consistent statistically significant differences in the numbers of different groups of microorganisms, the activities of the enzymes, and the pH between soils planted with Bt and non-Bt corn. Numbers and types of microorganisms and enzyme activities differed with season and with the varieties of corn, but these differences were not related to the presence of the Cry proteins in soil. The Cry1Ab protein of Bt corn (events Bt11 and MON810) was detected in most soils during the 4 yr, whereas the Cry3Bb1 protein was not detected in soils of Bt corn (event MON863) expressing the cry3Bb1 gene.
The role earthworms play in soil fertility is under increasing scientific scrutiny, especially in light of the fact that farmers are seeking to reduce soil tillage. However, there are many discrepancies in earthworm sampling methods. The aim of this study is to compare the efficiency of three chemical expellants (formaldehyde, commercial ‘hot’ mustard and allyl isothiocyanate, abbreviated AITC), with two sampling methods: (i) a simple method that consisted in spreading an expellant solution on the soil and retrieving earthworms that emerged at the soil surface, and (ii) a combined method that consisted in applying a chemical to expel earthworms and then hand-sorting the remaining earthworms from the block of soil. Sampling efficiency was measured in terms of earthworm density and biomass, for endogeic and anecic earthworms.With the simple method, a higher density of earthworms was sampled using formaldehyde and AITC than with mustard. Formaldehyde, AITC and mustard expelled not significantly different biomasses of 47.7, 31.9 and 20.5gm−2, respectively, on average over the three plots. The combined method did not yield a significantly different density or biomass with the different chemicals.Formaldehyde is toxic and commercial ‘hot’ mustard is difficult to standardise and inefficient when used without hand-sorting. Accounting for the accuracy of the sampling methods as well as the toxicity of the chemicals to users and soil organisms, AITC appears to be a reliable and promising chemical expellant whether or not in combination with hand-sorting. Its use would be a step towards standardizing earthworm sampling methods.
The entomopathogenic bacterium Bacillus thuringiensis (Bt) and its toxins are extensively used for pest control purposes in agriculture, forestry and public health programmes since the 1930. In addition to spray formulations, transgenic plants containing Bt genes for the expression of the toxins (Bt plants) are commercially available since the mid 1990s and are grown on an increasing percentage of the global agricultural area. A main reason for the importance of Bt as a pesticide is the assumed environmental safety concluded from the high specificity of its endotoxins (Cry proteins) towards a limited number of target organisms, mostly distinct groups of pest insects. While the mode of action of the Cry toxins in these susceptible target insects is well studied, Bt experts claim that several details are still not understood well enough. Although there is considerable experience with the application and the environmental safety of Bt sprays, a number of research papers were published in the past that did report adverse effects on non-target organisms. These and the widespread use of transgenic Bt plants stimulated us to review the published laboratory feeding studies on effects of Bt toxins and transgenic Bt plants on non-target invertebrates. We describe those reports that documented adverse effects in non-target organisms in more detail and focus on one prominent example, the green lacewing, Chrysoperla carnea. Discussing our findings in the context of current molecular studies, we argue firstly that the evidence for adverse effects in non-target organisms is compelling enough that it would merit more research. We further conclude from our in-depth analysis that the published reports studying the effects of Bt toxins from Bt pesticides and transgenic Bt plants on green lacewing larvae provide complementary and not contradictory data. And, finally, we find that the key experiments explaining the mode of action not only in this particular affected non-target species but also in most other affected non-target species are still missing. Considering the steadily increasing global production area of Bt crops, it seems prudent to thoroughly understand how Bt toxins might affect non-target organisms.
Leaf litter from 8 species of tree, shrub or herb, ranging in lignin content from 3.4-20.5%, was allowed to decompose in microcosms for up to 4 mo (equivalent to 1.5-2 yr decay in the field). Nitrogen content and the C:N ratio were the best predictors of mass loss rate, and were substantially better than the ligin:N ratio. However, when regressions were tested using pine needles (lignin content 26.2%), the C:N ratio and N content badly underestimated mass remaining, while lignin content and the lignin:N ratio overestimated it by <2%. Regressions of initial lignin content or lignin:N ratio on mass remaining improved from 2 to 4 mo decomposition, while those of N content grew worse, illustrating succession of N to lignin control of decomposition rate. -from Authors
Laboratory toxicity studies were conducted to determine the subacute effects of Bt Cry1Ab corn leaf material on nontarget soil organisms. Survival and growth were measured for an earthworm, Eisenia fetida Savigny, and survival and reproduction were measured for a springtail, Folsomia candida Willem. The organisms were provided leaf material of two Bt11 corn varieties, two Mon810 corn varieties, and the isolines of each, in a soil system and monitored for 28 d. An assay control treatment of an optimal food and a reference control treatment, using the herbicide pendimethalin, were used to provide a context for the observed results. Basic nutritional data of protein, fat, and sugar content were analyzed for each food type. Greater growth was observed for E. fetida in two Bt varieties, Bt11 90-d and Mon810 108-d, compared with their isolines. F. candida receiving Bt11 90-d isoline material had more offspring compared with those in the corresponding Bt line, but no other pairs were different. Time to reproduction of F. candida was only affected by the reference control treatment. Both protein and sugar content were found to correlate significantly with growth for E. fetida, but the nutritional parameters were not found to correlate with the effects observed for F. candida. These results indicate that there is little direct hazard from Bt corn leaf material to E. fetida and F. candida but that differences in nutritional parameters of the Bt lines and the isolines may lead to differences in the effects on nontarget organisms.
Corn engineered to produce the Cry3Bb1 protein from Bacillus thuringiensis Berliner (Bt) has provided unprecedented control for corn rootworm (Diabrotica virgifera virgifera Le Conte). However, accumulation and persistence of plant-produced Bt protein in soils may occur where Bt crops are repeatedly grown and residues of the crop plants are incorporated into the soil. If Bt protein is released into the soil rhizosphere, it may affect soil organisms. Studies were conducted to determine the effect of Bt or non-Bt corn roots and biomass on the weight and mortality of the earthworm, Lumbricus terrestris L. with different exposure methods and times. Enzyme-linked immunosorbent assay (ELISA) was conducted to determine if the Cry3Bb1 protein was present in the soil from the gut and excreta of earthworms. Results of these studies showed that there were no significant differences in weight and percent mortality of earthworms in soil planted or not planted with Bt and non-Bt corn or in soil containing ground air-dried biomass of Bt and non-Bt plants. Cry3Bb1 protein was detected in the soil from pots and the gut and excreta of earthworms exposed to Bt roots or biomass, whereas it was absent in soil from pot, the gut and excreta of earthworms exposed to roots or biomass of non-Bt corn. There was no significant difference in the amount of the protein recovered from pots or the gut or excreta of earthworms exposed to soils containing Bt roots or biomass for 12 or 33 d.
Nontarget risk assessment for transgenic crops should be case specific, depending on the plant, the transgene, and the intended
release environment. We propose an ecological risk-assessment model that preserves the strengths and avoids the deficiencies
of two other commonly used models, the ecotoxicology and nonindigenous-species models. In this model, locally occurring nontarget
species are classified into groups according to their ecological function. Within each group, ecological criteria are used
to select the species that are most likely to be affected by the transgenic crop. Initial experimental assessments are conducted
in the laboratory and consist of two kinds of test: toxicity tests using purified transgene product, and whole-plant tests
using intact transgenic plants. For nontarget natural enemy species, it will also be important to evaluate both direct bitrophic
impacts and indirect tritrophic impacts.
Corn engineered to produce the Cry3Bb1 protein from Bacillus thuringiensis (Bt) kumamotoensis has provided unprecedented control for corn rootworm (Diabrotica spp.). However, the Bt protein may be released in soil by root exudates or decaying plant residues that may affect soil organisms. Field studies were conducted to determine the abundance of surface and below-ground nontarget arthropods in fields planted with Bt or non-Bt corn for the first year or planted over 3 consecutive yr. Results of these studies showed that there were no significant differences in numbers of surface and below-ground arthropods in soil planted with Bt and non-Bt corn at any of the studied locations. Enzyme-linked immunosorbent assay (ELISA) showed no detectable Cry3Bb1 protein in any of the soil samples collected in a field planted with a Bt corn hybrid and its non-Bt isogenic hybrid for the first year or planted over 3 consecutive yr near Manhattan, KS. However, a small amount of Cry3Bb1 protein (3.38–6.89 ng/g dry soil) was detected in the soil samples collected from an area near plants in a Bt corn field that was planted for the first year near Scandia, KS. These findings indicate that the Cry3Bb1 protein released from root exudates or decaying plant residues does not persist and is rapidly broken down in the soil. The rapid degradation of Cry3Bb1 in soil results in none or trace amounts of protein being detected by ELISA.
Genetically modified Bacillus thuringiensis Berliner (Bt) maize (Zea mays L.) expressing Cry toxins against various target pests is now grown on more than 16 million hectares worldwide, but its potential
effects on the soil ecosystem need to be further investigated. In an 8-month field study, we investigated the effects of Bt
maize expressing the Cry1Ab protein on both the soil community and maize residue decomposition. We used litterbags with three
different mesh sizes (20, 125, and 5,000μm) to investigate potential effects of different soil organism groups on the decomposition
processes. Litterbags were incorporated into the soil in fall into a field that had previously been planted with non-Bt maize
and subsamples were removed monthly. The dry weight of the remaining residue was measured for all bags. Bt and non-Bt maize
decomposed similarly in large mesh bags, which allowed the whole soil organism community to enter and interact with each other.
In contrast, Bt maize decomposed significantly faster than non-Bt maize at some sample dates in winter in bags with small
and medium mesh sizes. At the end of the experiment in late spring, however, there was no significant difference in the amount
of maize plant residues remaining for any of these three mesh sizes. Additionally, soil organisms from bags with the largest
mesh size were identified. The most frequent taxa extracted were collembolans (Isotomidae, Tullbergiidae, Entomobryidae),
mites (Gamasina, Oribatida), and annelids (Enchytraeidae). Three of these taxa were extracted in higher numbers from non-Bt
than Bt residue (Tullbergiidae, Gamasina, Enchytraeidae), while there was no difference in the number of individuals extracted
for the remaining three taxa. Our results do not show major changes in the decomposition of Bt maize residue and in the composition
of the soil organism community. However, further studies are needed that assess the impact of the continuous release of Cry1Ab
via root exudates and plant biomass on the soil ecosystem.
A worldwide survey of earthworms in the humid tropics revealed that 51 exotics and 151 native species are commonly found in tropical agroecosystems. On the basis of frequency records and climatic and edaphic ranges, 21 exotics and 27 native species have been selected as possible candidates for manipulation. A multivariate analysis separated these species into four groups : (i) native species with wide edaphic and medium climatic tolerances ; (ii) exotic species with wide climatic and edaphic tolerances ; (iii) native and exotic species with narrow edaphic tolerances but more resistant to climatic variations ; and (iv) native species with limited tolerance for climatic and edaphic variations. Regarding management, species of group (ii) seem to be the most adaptable, both at regional and local levels (multipurpose species) ; group (i) can be managed for specific climatic conditions whereas group (iii) should be managed in specific soil environments. Species of group (iv) may only be managed at a very local scale. (Résumé d'auteur)
An assessment was made on the effect of inserting the cry1A(b) (Bt) gene of Bacillus thuringiensis into the genoma of two corn hybrids (the newly-developed hybrid from Cargill Semences identified as CR and the traditional B73xMo17) on the analytical composition, the in vitro rumen degradability and the mycotoxin contamination of the plant. Transgenicity changed the plant chemical composition as a function of the recipient genotype: starch was increased in the CR-Bt + plant (70.4% vs 73.3%; P < 0.10) whereas higher lignin content (6.3% vs 7.3%; P < 0.05), lower protein (7.7% vs 7.1%; P < 0.10) and soluble nitrogen (34.8% vs 26.9%; P < 0.10) contents were observed for the B73xMo17-Bt + plants. When not considering the hybrid pedigree there was a tendency (P < 0.1) toward a lower protein content in the Bt + corn seeds (9.2 vs 8.2%) and a higher sugar content in stalk and leaves (2.9% vs 5.7%). The stover degradation increased in the CRBt + variety, probably as the consequence of the higher content of lower structured carbohydrates. Transgenic plants had less ergosterol and fumonisin content than standard corn, suggesting a reduced susceptibility to mould attack.
As early as 1908, Arldt concluded from considerations of palaeographic changes in land and sea distribution ofpresent day earthworm species that terricole oligochaetes first appeared in the Upper Triassic. Michaelsen (1921), interpreting earthworm distribution in terms of Wegner’s theory of continental drift, put their origin in the Carboniferous period and Wilcke (1955), from considerations of earthworm ecology, concluded that mull-forming, soil-dwelling worms could not have evolved before deciduous forests existed in the late Cretaceous.
The changes in the environment caused by man’s industrial and agricultural activities have influenced earthworm populations in many parts of southern Africa. These changes have been considerable and many former specimen localities of fifty or even less years ago cannot be found today (Liungström, 1972; Du lessis, 1978). This chapter relates the present distribution of endemic and exotic species to climate, changes in vegetation following development for agriculture, and the physiology and ecology of individual species.
The inception, ring-testing and standardisation of the acute earthworm toxicity test (OECD 1984), has been at catalyst for the emergence of earthworms as one of the key organisms in (environmental) toxicology. In recognition of this role, there have now been three International Workshops on Earthworm Ecotoxicology (Sheffield in 1991, Amsterdam in 1997 and Aarhus, in 2001). At each workshop delegates met to outline recent work and identify future priorities. At the end of each workshop, recommendations were drawn up both to act as a summary of current knowledge and as initiators for future research. in this paper we briefly review progress in respect of these recommendations. Overall, advances have been made in many areas. Test procedures for laboratory and field toxicity tests have been improved and diversified, thus allowing specific studies not covered by the original OECD (1984) procedure. Further, there is now improved understanding of factors that can modify the effects of chemicals in dynamic ecosystems and also of the mechanistic basis of toxicosis (although many uncertainties still remain in these areas). One notable area where progress has been slower is development of a linked earthworm ecotoxicology community. In particular recommendations to develop comprehensive databases have yet to be implemented.
(1) The effects of bush clearing, cultivation and crop protection with DDT on earthworms surface casting activity and populations were monitored over a 4-year period in southern Nigeria. (2) Surface casting activity by Eudrilus spp. was low in uncleared bush plots but increased progressively from year to year in cultivated plots, untreated with DDT. Casting activity in DDT-treated plots remained at a low level. Hyperiodrilus sp. surface casting activity was significantly reduced in all cultivated treatments compared with bush plots. (3) Despite reduced casting activity in DDT-treated plots, population studies revealed no significant differences in total earthworm populations between the three cultivation treatments in terms of numbers and biomass per unit area.
(1) Under shifting agriculture (jhum) in north-east India, Tonoscolex horaii (Stephenson) and Amynthas diffringens (Baird) were sampled during cropping and fallow phases up to 15 years old, while Nelloscolex strigosus (Gates) and Drawida assamensis (Gates) occurred only in samples from fallows 5 or 15 years old. (2) Population size declined significantly after slashing and burning. (3) Seasonal fluctuations with maximum population size during the wet season were observed for all species except Amynthas diffringens, which peaked during the winter. (4) Population size was significantly correlated with soil moisture, temperature and organic matter. (5) Wormcasts had higher pH and better nutrient status than soil. (6) Wormcasts are local concentrations of nutrients. In highly leached soils of the humid tropics, earthworm activity is beneficial because of rapid incorporation of detritus into the mineral soil.
Soil is the habitat of plant roots and of a diverse array of organisms - bacteria, fungi, protozoa and invertebrate animals - which contribute to the maintenance and productivity of agroecosystems. As intensification occurs, the regulation of functions through soil biodiversity is progressively replaced by regulation through chemical and mechanical inputs. However, the causal relationships between composition, diversity and abundance of soil organisms and sustained soil fertility are unclear. Furthermore, in tropical agricultural systems undergoing intensification, large numbers of farmers have limited access to inputs, and therefore the maintenance and enhancement of soil biodiversity may be particularly relevant to such farmers. In this paper we propose a number of hypotheses which could be tested to explore the relationships between agricultural intensification, biodiversity in tropical soils and ecosystem functions. We also provide a conceptual framework within which such hypotheses can be tested. (Résumé d'auteur)
1. In an ecological approach to risk assessment, population models may play an important role. Our population dynamical models take into account the complex life history of earthworms, as well as a particular ecological interaction (predation). 2. Sublethal impact of pesticides is quantified at the individual level in terms of impaired vital rates, i.e. growth, maturation and reproduction. A simple model for the energetic relationships underlying these vital rates quantifies toxic stress mechanistically through proportionality constants relating size to energetic costs of maintenance, growth, food intake and production of offspring. 3. Risk is defined at the population level. Risk resulting from chronic exposure relates to reductions in (equilibrium) density, changes in population size- and age-structure, and probability of surpassing an extinction threshold. Risk posed by a single or intermittent application of a highly degradable pesticide is defined in terms of extinction probabilities and recovery times, and related to pesticide decay and initial applied dose. 4. The models are individual-based and complementary. A deterministic partial differential equation model is used to derive equilibrium properties of the system analytically and to investigate the general dynamic behaviour. An individual-by-individual model shows how this behaviour is influenced by demographic and environmental stochasticity. 5. Results obtained for two species, Lumbricus rubellus and L. terrestris, indicate that both are sensitive to pesticides affecting the energy available for individual growth, as opposed to the amount of energy available for reproduction. Retarded growth impedes individuals in reaching adulthood. This juvenile delay regulation translates from individual performance to population demography. 6. Life-history characteristics appear to make L. terrestris more sensitive to toxic stress than L. rubellus, resulting in longer population recovery times. 7. The insights obtained from the models and the way results depend on model assumptions, are discussed, and compared to the little available observational and experimental evidence. Extensions enabling a full ecological risk assessment for pesticide use are identified. Establishing an explicit relationship between ambient concentration and individual performance seems mandatory prior to use of the models as predictive tools.
Two field experiments had been conducted in Huantai County, Shandong Province, east of China, with an effort to understand the impact of agricultural intensification on earthworm diversity and population density. Seven species of earthworms were identified in the two experiments. Average earthworm populations in the higher fertility soil (experiment B, 1.83% organic matter) were relatively abundant, with a population density of 105 indiv./m2 and biomass of 57 g/m2. Aporrectae trapezoids was the most dominant species. In the lower fertility soils (experiment A, 1.43% organic matter) the population density was only 51 indiv./m2 and the average biomass was 30 g/m2. Drawida gisti was the most dominant species. For both the experiments A and B, organic fertilizer (OF) and crop straw return increased earthworm abundance. The impact of chemical fertilizer (CF) on the earthworm population was found to depend on the amount of organic input. In experiment B, the earthworm biomass decreased when only winter wheat (Triticum aestivum) straw was input at three CF application levels. However, while both winter wheat straw (WS) and corn (Zea mays) stalk returned, there was no negative correlation between CF and earthworm density and biomass.
European earthworms are invading previously worm-free hardwood forests across Minnesota and the Great Lakes region. In many of these forests, earthworm invasions have been associated with the loss of a previously thick forest floor. The ability of earth- worms to alter and control ecosystem processes has been demonstrated in agricultural systems, but the dynamics and impact of these invasions in native forest ecosystems is largely unknown. The impacts of earthworm invasion are expected to be related to the size and species composition of the earthworm population because different species have dif- ferent habitat and feeding preferences. We identified four sugar maple dominated forests in north central Minnesota in the Chippewa National Forest with active earthworm invasion. In each site a sample grid of 45 points (30 150 m) 10 m apart in three parallel transects with 15 points each was established that spanned a visible leading edge of invasion. Over four years earthworm populations and forest floor thickness were sampled across all tran- sects, thus providing both a space-for-time assessment of decadal scale successional dy- namics and a four-year window into shorter time changes. We found a succession of earth- worm species across the visible leading edge due to different patterns of colonization by different earthworm species. Marked increases in space and time in earthworm biomass were associated with the development of discrete transition zones where forest floor thick- ness decreases to zero in as little as 75 m from areas that have forest floor layers up to 10 cm thick with advancement of the visible leading edge of up to 30 m in four years at three of the study sites. The epi-endogeic speciesLumbricus rubellus led to the most rapid removal of forest floor material during initial invasion. Epigeic and epi-endogeic species of earth- worms may facilitate the establishment of other species of earthworms leading to the establishment of stable populations of endogeic and anecic species, which prevent recovery of the forest floor.
The effects of the invasion of the epigeic earthworm Dendrobaena octaedra (Savigny) on soil structure, organic matter, total N and C, and microbial activity were studied over 2 years in a Pinus contorta Dougl. ex Loud. var. latifolia Engelm. forest. During the experiment gradients of earthworm abundance (0 to 3349.m(-2)) and biomass (0 to 40 g dry wt..m(-2)) were observed. Organic matter content, total nitrogen, carbon, basal respiration (per gram soil and per gram organic matter), and metabolic quotient (qCO(2)) decreased with increasing worm biomass, suggesting that D. octaedra is reducing nutrient availability for the microbes, and that microbial efficiency of carbon use is increasing. We suggest that nutrient availability for microbes was reduced through earthworm stimulation of microbial decomposition of organic matter, direct consumption of organic matter by worms (not measured), and stabilization of carbon through binding to clays in casts (not measured). After 2 years pine needle litter decomposition was significantly higher in the two plots with the highest worm biomass than in the two plots with the lowest worm biomass.
The efficiency of using mustard extract as a repellent for earthworm sampling was investigated for two contrasting earthworm species. For the anecic Anisochaetae sp., a deep burrowing species which created vertical burrows, mustard extract produced a 67% higher abundance than the formalin (74 versus 44 m—2). Handsorting underestimated abundance by 21% and biomass by 67% because of its failure to include the adults /subadults which escaped quickly to below 10 cm depth but were effectively sampled by using mustard. Excessively concentrated mustard extract reduced sampling efficiency by reducing the number of juveniles. The most optimal concentration was achieved by shaking 106 g dry mustard powder in 1 L of 5% acetic acid overnight which was then diluted with water in the ratio of 15 mL to 1 L.
For Aporrectodea trapezoides, an endogeic species which tends to create horizontal burrows not all directly connected to the surface, using mustard extract was a completely ineffective method of sampling compared to handsorting because most of the earthworms were adversely affected and remained in the 0–10 cm layer. From these results, mustard extract at optimal concentration is a more efficient and environmental friendly repellent for only certain earthworm species, particularly the anecic earthworms.
The changes in the population of earthworms, predominantly Aporrectodea trapezoides, induced by cultivation and cropping of Brussels sprouts, followed by a return to pasture, were monitored for a period of more than 2 years in a South Australian soil. Worms were hand-sorted from 0.5 m2 areas at monthly intervals during 3 winter/spring periods, and during irrigation of the crop throughout one summer. Peak numbers in pasture reached 240 m−2 (biomass 66 g m−2) during winter/spring of 1999, were reduced to a very few individuals (13 m−2) by cultivation in late September 1999, but increased to 578 m−2 (biomass 62 g m−2) from January to April 2000 (the warm summer months) under irrigation in a similar manner to a normal winter and spring period (June to October). The loose matrix of the cultivated soil and abundant organic matter provided excellent conditions for reproduction, hatching and growth of earthworms. Ploughing in crop residues reduced the earthworm population to 32 m−2, then there was a steady increase in the number and size of the earthworms during the following winter to 168 worms m−2 in October, with a mean weight of 450 mg and a biomass of 75 g m−2. No earthworm activity occurred during the very hot dry summer of 2000–2001. However, in June 2001 after opening rains, the number of earthworms found was very similar to that of the previous late spring (178 vs. 168), but the average weight had practically halved (451 mg vs. 238 mg). Nearly all the earthworms had survived the summer months despite a loss of almost 50% of their body weight. During the winter of 2001, the population increased in average weight, with frequent appearance of large breeding adults, indicative of a mature population.
Tabasco, in southeastern Mexico, is one of the states where deforestation has occurred as a result of the implementation of agricultural systems. Only 4% of its territory is tropical rainforest and areas used for forestry. For this reason, it is important to study the soil fauna in these natural relicts. Sixteen sites (4 natural and 12 managed systems) were studied in order to identify earthworm species communities, using the TSBF method. Nineteen species were found, 14 native and 5 exotic, belonging to the families Megascolecidae, Glossoscolecidae and Ocnerodrilidae. Sites that presented the highest species diversity were Tropical rain forest (9), which also contained high organic matter content (11.9±5.7%), total nitrogen (0.66±0.2%), and available phosphorus (18±7.56mgkg−1), and Traditional cacao cultures (13). The highest earthworm biomass was found in a tree plantation of Mangifera indica, and the highest density was observed in riparian vegetation. A significant relationship was observed between earthworm density and clay content (Spearman's rho 0.3, P=0.01).
An assessment of the efficiency of the mustard extraction method to quantify the total earthworm community structure on UK earthworms was carried out on a permanent pasture in Bedfordshire, UK. Earthworms were collected using mustard extraction and control treatments. Numbers and community structure of worms expelled from soils after surface applications of expellants were determined, and underlying soil from each replicate was hand-sorted to recover residual earthworms. The mustard-based treatment was the only method to expel earthworms to the surface, and 35.7% of the extant population emerged. The apparent earthworm community structures expelled indicated that mustard extraction was biased towards large, sexually mature anecic earthworms. This is likely due to the connectivity of burrows of these earthworms to the surface and hence a biased incursion of mustard solution down such channels. The mustard extraction technique is therefore inappropriate where accurate assessment of earthworm communities is required.
Between June 1988 and October 1989 the effect of soil compaction on abundance and biomass of active lumbricids was investigated in a longterm field experiment under spring-wheat and winter-barley. Seven plots were subjected to loads by agricultural machinery under conditions simulating three common kinds of agricultural practice and compared to an unloaded control plot (Table 1). The dominant species of the investigation area, Aporrectodea caliginosa and A. rosea (99.3% of total individual number) had their highest activity and biomass in the uncompact control plot. Lowest individual numbers were found in the extremely loaded wheel-track and the conservation tillage area. The extensive cultivation of this area began just at the start of the field experiment, so that a greater earthworm population had not had time to establish itself.In pot experiments the activity of the endogeic species A. caliginosa was investigated in tripartioned soil columns (40 cm long × 19 cm wide), each differently compact to pore volumes (pv) of 37.5, 42.5, 47.5 and 56%. A significantly higher activity, measured as the length and the number of the burrows visible from outside, was found in the lighter substrates. The volume number extent of earthworm burrows was as much as 2 times higher in the 47.5 and 56% pv columns than in the more compact 42.5 and 37.5% pv columns.
The density and seasonal distribution patterns of three to five earthworm species was observed in relation to crop rotations during a period of 2 years in three localities ((a) Sun temple site; (b) Small tank site; (c) Dak bunglow site) in the rainfed upland agricultural system of central Himalayan district of Almora, India.Earthworm species composition at Sun tample site was different from the Dak bunglow site and Small tank site. Drawida sp. was dominant at the Sun tample site whereas Lennogaster yeicus and Metaphire holutii were dominant at the Dak bunglow site. Maximum earthworm density (200 m −2) was recorded in the late rainy season in the rice crop mixture and in Eleusine coracana (finger millet) crop mixture (335 m−2) sown following the harvest of winter wheat crop. Ploughing, harrowing and cult-discing the soils in the agricultural system during crop rotation had adverse effect on earthworm species populations. Ploughing back of crop byproducts along with the addition of the organic manure encouraged increase in the earthworm populations.
As studied at the Hubbard Brook Experimental Forest, rate constants (k) for annual leaf mass loss ranged from -0.08 to - 0.47. The rate constants had a negative linear correlation with the ratio of initial lignin concentration to initial N concentration. Decomposition dynamics of the litter materials were described by inverse linear relationships between the percentage of original mass remaining and the N concentration in the residual material. Initial lignin concentration was highly correlated with the slope of the inverse linear relationship for each of the litter types. -from Authors
There have been inconsistent reports that maize (Zea mays L.) hybrids with the Bacillus thuringiensis (Bt) cry1 Ab transgene contain more lignin than non-Bt hybrids of similar genetic background. Our objective was to evaluate the impact of the cry1 Ab transgene on lignin concentration (using three different assays), yield, and forage quality traits of maize. Replicated trials were conducted at four locations in Minnesota with 12 commercial hybrids (three MON810 and three Bt11 cry1 Ab transgene event hybrids, and respective near-isogenic controls). Whole plants and the fourth elongated, aboveground internodes were harvested at silage maturity. Samples were analyzed for crude protein, starch, neutral detergent fiber (NDF), acid detergent fiber, 24- and 96-h in vitro ruminal NDF digestibility, and lignin (acid detergent, Klason, and acetyl bromide). European corn borers (Ostrinia nubilalis Hübner) were not controlled and damage was limited to the non-Bt hybrids, averaging 1.5 internodes plant-1 with tunnels. Environment and environment x hybrid interactions affected all measures of maize performance and quality, but comparisons of non-Bt/Bt hybrid pairs, for both whole plants and internodes, found no consistent differences in yield, nutrient content, in vitro ruminai NDF digestibility, or lignin concentration. Differences in lignin concentration were infrequent, small in magnitude, and inconsistent between a few non-Bt/Bt hybrid pairs at individual locations. Two non-Bt/Bt hybrid pairs did not differ in lignin concentration at any location. Contrary to some earlier reports, presence of the cry1 Ab transgene did not alter lignin concentration or other forage quality traits of maize stover in commercial maize hybrids.
The interactions of genetically modified (GM) crops with soil species and ecosystems is complex, requiring both specific and broad spectrum assessments. In the ECOGEN project we undertook experiments at three scales of increasing complexity, using Bt maize expressing the Cry1Ab protein from Bacillus thuringiensis as an example. Test species were selected for laboratory-scale experiments to represent taxonomic groups that we could also monitor at glasshouse and field scales (e.g., nematodes, protozoa, micro-arthropods, earthworms, and snails). In the laboratory, single species were exposed to purified Cry1Ab protein or to Bt maize leaf powder incorporated into simplified diets under controlled conditions. In the glasshouse, multiple test species and soil microbial communities taken from ECOGEN's field sites were exposed to Bt maize plants growing under glasshouse or mesocosm conditions. In the field, evaluations were conducted on our selected indicator groups over multiple sites and growing seasons. Field evaluation included assessment of effects due to the local environment, crop type, seasonal variation and conventional crop management practice (tillage and pesticide use), which cannot be assessed in the glasshouse. No direct effects of Cry1Ab protein or Bt leaf residues were detected on ARTICLE IN PRESS
The effects of the invasion of the epigeic earthworm Dendrobaena octaedra (Savigny) on soil structure, organic matter, total N and C, and microbial activity were studied over 2 years in a Pinus contorta Dougl. ex Loud. var. latifolia Engelm, forest. During the experiment gradients of earthworm abundance (0 to 3349.m-2) and biomass (0 to 40 g dry wt.m-2) were observed. Organic matter content, total nitrogen, carbon, basal respiration (per gram soil and per gram organic matter), and metabolic quotient (qCO2) decreased with increasing worm biomass, suggesting that D. octaedra is reducing nutrient availability for the microbes, and that microbial efficiency of carbon use is increasing. We suggest that nutrient availability for microbes was reduced through earthworm stimulation of microbial decomposition of organic matter, direct consumption of organic matter by worms (not measured), and stabilization of carbon through binding to clays in casts (not measured). After 2 years pine needle litter decomposition was significantly higher in the two plots with the highest worm biomass than in the two plots with the lowest worm biomass.
Pit digging and manually revising soil blocks is a frequently used method used for field studies of earthworm communities. The aim of this study was to compare the efficiency of hand-sorting (HS) to extract small earthworms, ca. 0.2 g, and the usefulness in studies of population dynamics and cohort analysis. Many earthworms are not recovered when revising manually the soil. Factors include soil characteristics, i.e. moisture, texture, etc. and also a human factor, which is more relevant if the study is conducted in the long-term. We used data collected in a field study of earthworm communities during 2 years in the savannas of Colombia. Small soil blocks (20 × 20 × 20 cm) were dug out in order to collect the smallest earthworms by washing-sieving (WS) and compare the results with the standard HS of large monoliths (100 × 100 × 50 cm). In fact, this methodology has rarely been addressed in earthworm population field studies. Our results showed that HS efficiency varied owing to the species and ranged from 31.4% up to 100% in the savanna and from 44% to 80% in the pasture, for two small species, i.e Aymara n. sp. (epigeic) and Ocnerodrilidae sp. (endogeic). In the case of the Glossodrilus n. sp. (endogeic) these values were similar, i.e. 51.7% and 58.1%, in the savanna and pasture, respectively. We also used frequency tables to calculate the average efficiency of HS 1 m 2 soil cores for each weight class in each species in order to obtain a population density correction factor. This allowed us to make corrections in earthworm density in the histograms for population dynamics analysis. We conclude that this method should be the modus operandi in long-term earthworm demography studies.
In the last decade the invasion of European earthworms into previously worm-free glaciated areas of North America has stimulated research into their impacts on native forest ecosystems in the region. As a first approximation, the impacts of invading earthworms are related to their biomass. However, direct measurements of biomass can be significantly affected by the moisture conditions under which the earthworms are collected and their relative gut contents. Ash-free dry mass is the best standardized measure of earthworm biomass, but requires the destruction of specimens. This paper presents five allometric equations that allow for estimation of ash-free dry biomass based on length (mm) measurements for European earthworm species (Lumbricidae) commonly seen in the United States.
The efficiency of mustard as a vermifuge for estimating earthworm populations or collecting earthworms for laboratory studies was compared with that of formalin, potassium permanganate and household detergent. Mustard was as efficient as potassium permanganate and both these substances were better than formalin. Household detergent was an extremely poor vermifuge. Mustard does not kill earthworms as does potassium permanganate, and unlike formalin it is not carcinogenic and does not have phytotoxic effects on clover. -from Author
Effects of soil fauna on soil quality are largely unknown. Our objective was to learn whether long-term soil management has significantly affected earthworm species and populations at two Iowa locations. Soil cores were collected in fall 1989, spring 1990, and fall 1990 from a long-term tillage study in Polk County, Iowa, involving monoculture of corn (Zea mays L.) with either no-tillage, fall disking, fall chisel plowing, or fall moldboard plowing. Species found were Lumbricus terrestris (L), Octolasion tyrtaeum (Savigny), Aporrectodea trapezoides (Duges), A. turgida (Eisen), and A. tuberculata (Eisen), with O. tyrtaeum dominant across all treatments. As the amount of tillage increased, the number of earthworms generally decreased. InBoone County, Iowa, we compared the populations of mature and immature earthworms and cocoons on two adjacent fields, one managed conventionally, the other managed with an alternative farming system for more than 20 years. The predominant species was A. tuberculata. Regardless of management practice, the most worms were found in Canisteo soil on the toeslope landscape position.
This chapter discusses the following procedures for risk assessment in Bt cotton using the non-target risk assessment model developed by scientists of the GMO ERA Project ("International Project on GMO Environmental Risk Assessment Methodologies", which is a continuation of the GMO Guidelines Project, which was launched by scientists of the International Organization for Biological Control Global Working Group on "Transgenic Organisms in Integrated Pest Management and Biological Control"): (1) identify relevant functional groups of biological diversity associated with adverse effects, (2) list and prioritize species or ecological processes, (3) identify potential exposure pathways and adverse effects pathways, and use these to formulate and prioritize risk hypotheses, and (4) develop an analysis plan and suggest designs for experiments to test risk hypotheses
The objective of this experiment was to determine the effects of earthworms on soil N pools and plant growth in soybean and maize agroecosystems. The species and number of individuals in earthworm communities were manipulated in plot-scale field enclosures (2.4 m × 1.2 m) by first reducing earthworm populations within enclosures with carbaryl pesticide, and then adding earthworm treatments to the enclosures. Soybean was grown in the enclosures in the first year and stover maize in the second year.The success of earthworm manipulations in field enclosures was affected by climate conditions and available food resources. The endogeic earthworm species Aporrectodea caliginosa was dominant in all enclosures, while introduced anecic Lumbricus terrestris earthworms had poor survival. In the first season, when climate conditions were favourable for earthworm survival and growth, there was a significant (P < 0.05) linear increase in soil mineral-N and microbial biomass N concentrations in the 0–15 cm depth of enclosures with more earthworms. Similarly, soybean grain and grain-N yield was significantly (P < 0.05) greater in enclosures with the largest earthworm populations than the control which had no earthworms added. In the second season, when climate conditions were less favourable, there was no effect of earthworms on soil N pools or maize plants, probably due to poor survival of introduced earthworms.
Earthworms have been termed ‘ecosystem engineers’ (sensu [Jones, C.G., Lawton, J.H., Shachak, M., 1994. Organisms as ecosysem engineers. Oikos 69, 373–386.]) because of the important roles they play in the soil. As a consequence, it is assumed that if earthworms change their behaviour following exposure to pesticides or pollutants this could have a drastic impact on soil functioning. To test this assumption under laboratory conditions, we studied the burrow systems made by two earthworm species (the anecic Aporrectodea nocturna and the endogeic Allolobophora icterica) in artificial soil cores containing imidacloprid, a widely used neonicotinoid insecticide. After 1-month incubation period, the macropores created in the soil core were analyzed by tomography. In order to further characterize transfer properties associated with burrow systems gas diffusion measurements were also carried out. The burrow systems made by the two earthworm species were very different: A. nocturna made more continuous, less branched, more vertical and wider burrows than A. icterica. Some changes to A. nocturna burrow systems were observed after exposure to imidacloprid (they made a smaller burrow system and burrows were more narrow), but only at the highest concentration of imidacloprid used (0.5 mg kg−1). A. icterica worms were more sensitive to imidacloprid and many differences in their burrow systems (length, sinuosity, branching rate and number of burrows) were observed at both concentrations tested (0.1 and 0. 5 mg kg−1). As a consequence, the continuity of the burrow systems made by both species was altered following imidacloprid treatment. Gas diffusion through the A. nocturna soil cores was reduced but no difference in gas diffusion was observed in the A. icterica soil cores.