Effects of plants genetically modified for insect resistance on nontarget organisms

Transgenic early japonica rice: Integration and expression characterization of stem borer resistance Bt gene

BACKGROUND

Transgenic insect-resistant rice offers an environmentally friendly approach to mitigate yield losses caused by lepidopteran pests, such as stem borers. Bt (Bacillus thuringiensis) genes encode insecticidal proteins and are widely used to confer insect resistance to genetically modified crops. This study investigated the integration, inheritance, and expression characteristics of codon-optimised synthetic Bt genes, cry1C* and cry2A*, in transgenic early japonica rice lines.

METHODS

The early japonica rice cultivar, Songgeng 9 (Oryza sativa), was transformed with cry1C* or cry2A*, which are driven by the ubi promoter via Agrobacterium tumefaciens-mediated transformation. Molecular analyses, including quantitative PCR (qPCR), enzyme-linked immunosorbent assay (ELISA), and Southern blot analysis were performed to confirm transgene integration, inheritance, transcriptional levels, and protein expression patterns across different tissues and developmental stages.

RESULTS

Stable transgenic early japonica lines exhibiting single-copy transgene integration were established. Transcriptional analysis revealed variations in Bt gene expression among lines, tissues, and growth stages, with higher expression levels observed in leaves than in other organs. Notably, cry2A* exhibited consistently higher mRNA and protein levels than cry1C* across all examined tissues and developmental time points. Bt protein accumulation followed the trend of leaves > stem sheaths > young panicles > brown rice, with peak expression during the filling stage in the vegetative tissues.

CONCLUSIONS

Synthetic cry2A* displayed markedly elevated transcription and translation compared to cry1C* in the transgenic early japonica rice lines examined. Distinct spatiotemporal patterns of Bt gene expression were elucidated, providing insights into the potential insect resistance conferred by these genes in rice. These findings will contribute to the development of insect-resistant japonica rice varieties and facilitate the rational deployment of Bt crops.

Safety assessment of subchronic feeding of insect-resistant and herbicide-resistant transgenic soybeans to juvenile channel catfish (Ictalurus punctatus)

Transgenic soybean is one of the most planted crops for human food and animal feed. The channel catfish (Ictalurus punctatus) is an important aquatic organism cultured worldwide. In this study, the effect of six different soybean diets containing: two transgenic soybeans expressing different types of cp4-epsps, Vip3Aa and pat genes (DBN9004 and DBN8002), their non-transgenic parent JACK, and three conventional soybean varieties (Dongsheng3, Dongsheng7, and Dongsheng9) was investigated in juvenile channel catfish for eight weeks, and a safety assessment was performed. During the experiment, no difference in survival rate was observed in six groups. The hepatosomatic index (HSI) and condition factor (CF) showed no significant difference. Moreover, comparable feed conversion (FC), feeding rate (FR), and feed conversion ratio (FCR) were found between transgenic soybean and JACK groups. Assessment of growth performance showed that the weight gain rate (WGR) and specific growth rate (SGR) of channel catfish were consistent. In addition, there were no changes in enzyme activity indexes (lactate dehydrogenase (LDH), total antioxidant capacity (T-AOC), aspartate aminotransferase (AST) and alanine aminotransferase (ALT)) in channel catfish among treatments. The research provided an experimental basis for the aquaculture feed industry to employ transgenic soybean DBN9004 and DBN8002 for commercial purposes.

Monitoring reduced accumulation and risk evaluation of Cry1Ca during food chain transfer from genetically engineered plant to endoparasitoid

BACKGROUND

The potential risk of insecticidal proteins produced by genetically engineered (GE) plants to nontarget organisms have long been an ecotoxicological concern. Apanteles chilonis, an important endoparasitoid of rice pest Chilo suppressalis, potentially is exposed to Bacillus thuringiensis (Bt) endotoxins through a food chain of transgenic Bt rice - C. suppressalis - A. chilonis, and thus, a rigorous risk assessment is urgently needed. Here, we combined a tri-trophic bioassay system with high-dose exposure approach using C. suppressalis hemolymph as the carrier of insecticidal protein to evaluate the biosafety of Cry1Ca to A. chilonis.

RESULTS

Cry1Ca protein could be transmitted and retained along the food chain and remains bioactive in the hemolymph of C. suppressalis during the pre-adult duration of A. chilonis. No significant differences in pre-adult period, male and female longevity, adult fecundity and weight, emergence rate nor sex ratio were observed when A. chilonis parasitized C. suppressalis feeding on cry1Ca rice compared with control treatment. However, the pupal period and weight were significantly prolonged and decreased. When A. chilonis parasitized C. suppressalis injected with a high dosage of Cry1Ca protein, no adverse effects on the life-history parameters, peroxidase (POD), superoxide dismutase (SOD) or glutathione reductase (GR) of A. chilonis were observed, demonstrating that the host quality mediates adverse effects during the food chain.

CONCLUSIONS

We confirmed that Cry1Ca posed no ecological risk to the nontarget endoparasitoid A. chilonis. This study may serve as an example for future risk assessment of transgenic crops to nontarget endoparasitoids. © 2023 Society of Chemical Industry.

Transgenic cotton expressing Cry1B protein has no adverse effect on predatory insect Propylea Japonica

The lady beetle Propylea japonica is a dominant natural predator of insect pests in farmland ecosystems and an important non-target indicator insect for the environmental safety assessment of GM crops. The commercial cultivation of GM crops may cause P. japonica to frequently be exposed to the Bt protein environment. In this study, the biological characteristics, enzyme activity, and expression levels of detoxification and metabolism in P. japonica were studied after Cry1B protein treatment. No significant differences were observed in developmental duration, emergence rate, or body weight at different ages after feeding larvae 0.5 mg/mL of Cry1B protein compared with the control. Furthermore, there were no significant differences in the activities of glutathione S-transferase (GST), catalase (CAT), and peroxidase (POD) after feeding 0.25 mg/mL and 0.5 mg/mL Cry1B protein. However, when the concentration of Cry1B protein increased to 1.0 mg/mL, the activities of the GST, CAT, and POD increased significantly. Compared with the control group, there were no significant differences in the expression levels of most detoxification metabolism related genes; only a few genes had changed expression levels at the individual concentrations (CYP345B1, CYP4Q2, CYP9F2, GST, and microsomal GST). Overall, these results suggest that Cry1B protein has little or no effect on the biological characteristics of P. japonica. Genes related to enzyme activity and detoxification are differentially expressed at high concentration stimulation. Therefore, this research suggests that the potential risks of Cry1B for the predator P. japonica are negligible.

Bee Stressors from an Immunological Perspective and Strategies to Improve Bee Health

Honeybees are the most prevalent insect pollinator species; they pollinate a wide range of crops. Colony collapse disorder (CCD), which is caused by a variety of biotic and abiotic factors, incurs high economic/ecological loss. Despite extensive research to identify and study the various ecological stressors such as microbial infections, exposure to pesticides, loss of habitat, and improper beekeeping practices that are claimed to cause these declines, the deep understanding of the observed losses of these important insects is still missing. Honeybees have an innate immune system, which includes physical barriers and cellular and humeral responses to defend against pathogens and parasites. Exposure to various stressors may affect this system and the health of individual bees and colonies. This review summarizes and discusses the composition of the honeybee immune system and the consequences of exposure to stressors, individually or in combinations, on honeybee immune competence. In addition, we discuss the relationship between bee nutrition and immunity. Nutrition and phytochemicals were highlighted as the factors with a high impact on honeybee immunity.

Dynamics of canopy-dwelling arthropods under different weed management options, including glyphosate, in conventional and genetically modified insect-resistant maize

The use of genetically modified varieties tolerant to herbicides (HT varieties) and resistant to insects (Bt varieties) in combination with application of a broad-spectrum herbicide such as glyphosate could be an effective option for the simultaneous control of weeds and pests in maize. Nevertheless, the possible impact of these tools on nontarget arthropods still needs to be evaluated. In a field study in central Spain, potential changes in populations of canopy-dwelling arthropods in Bt maize under different weed management options, including glyphosate application, were investigated. Canopy-dwelling arthropods were sampled by visual inspection and yellow sticky traps. The Bt variety had no effect on any group of studied arthropods, except for the expected case of corn borers-the target pests of Bt maize. Regarding the effects of herbicide regimes, the only observed difference was a lower abundance of Cicadellidae and Mymaridae on yellow sticky traps in plots not treated with pre-emergence herbicides. This effect was especially pronounced in a treatment involving two glyphosate applications. The decrease in Cicadellidae and Mymaridae populations was associated with a higher density of weeds in plots, which may have hindered colonization of the crop by leafhoppers. These differences, however, were only significant in the last year of the study. The low likelihood of the use of glyphosate- and herbicide-tolerant varieties for weed control triggering important effects on the nontarget arthropod fauna of the maize canopy is discussed.

ptxD/Phi as alternative selectable marker system for genetic transformation for bio-safety concerns: a review

Antibiotic and herbicide resistance genes are the most common marker genes for plant transformation to improve crop yield and food quality. However, there is public concern about the use of resistance marker genes in food crops due to the risk of potential gene flow from transgenic plants to compatible weedy relatives, leading to the possible development of “superweeds” and antibiotic resistance. Several selectable marker genes such as aph, nptII, aaC3, aadA, pat, bar, epsp and gat, which have been synthesized to generate transgenic plants by genetic transformation, have shown some limitations. These marker genes, which confer antibiotic or herbicide resistance and are introduced into crops along with economically valuable genes, have three main problems: selective agents have negative effects on plant cell proliferation and differentiation, uncertainty about the environmental effects of many selectable marker genes, and difficulty in performing recurrent transformations with the same selectable marker to pyramid desired genes. Recently, a simple, novel, and affordable method was presented for plant cells to convert non-metabolizable phosphite (Phi) to an important phosphate (Pi) for developing cells by gene expression encoding a phosphite oxidoreductase (PTXD) enzyme. The ptxD gene, in combination with a selection medium containing Phi as the sole phosphorus (P) source, can serve as an effective and efficient system for selecting transformed cells. The selection system adds nutrients to transgenic plants without potential risks to the environment. The ptxD/Phi system has been shown to be a promising transgenic selection system with several advantages in cost and safety compared to other antibiotic-based selection systems. In this review, we have summarized the development of selection markers for genetic transformation and the potential use of the ptxD/Phi scheme as an alternative selection marker system to minimize the future use of antibiotic and herbicide marker genes.

Quantitative and Predictive Genetic Parts for Plant Synthetic Biology

Plant synthetic biology aims to harness the natural abilities of plants and to turn them to new purposes. A primary goal of plant synthetic biology is to produce predictable and programmable genetic circuits from simple regulatory elements and well-characterized genetic components. The number of available DNA parts for plants is increasing, and the methods for rapid quantitative characterization are being developed, but the field of plant synthetic biology is still in its early stages. We here describe methods used to describe the quantitative properties of genetic components needed for plant synthetic biology. Once the quantitative properties and transfer function of a variety of genetic parts are known, computers can select the optimal components to assemble into functional devices, such as toggle switches and positive feedback circuits. However, while the variety of circuits and traits that can be put into plants are limitless, doing synthetic biology in plants poses unique challenges. Plants are composed of differentiated cells and tissues, each representing potentially unique regulatory or developmental contexts to introduced synthetic genetic circuits. Further, plants have evolved to be highly sensitive to environmental influences, such as light or temperature, any of which can affect the quantitative function of individual parts or whole circuits. Measuring the function of plant components within the context of a plant cell and, ideally, in a living plant, will be essential to using these components in gene circuits with predictable function. Mathematical modeling will be needed to account for the variety of contexts a genetic part will experience in different plant tissues or environments. With such understanding in hand, it may be possible to redesign plant traits to serve human and environmental needs.

The influence of transgenic (Bt) and non-transgenic (non-Bt) cotton mulches on weed dynamics, soil properties and productivity of different winter crops

The introduction of transgenic cotton (Bt-cotton) for controlling bollworms has resulted in increased production; however, the residual effects of mulches from Bt-cotton are poorly understood. Therefore, the current study evaluated the impact of Bt and non-Bt cotton mulches on soil properties, weed dynamics and yield of winter crops sown after cotton. Three different winter crops, i.e., wheat (Triticum aestivum L.), canola (Brassica napus L.) and Egyptian clover (Trifolium alexandrinum L.) and two mulch types, i.e., Bt mulch (obtained from Bt-cotton cultivars, i.e., 'CIM-616' and 'GH-Mubarik') and non-Bt mulch (obtained from non-Bt cultivars, i.e., 'CIM-620' and 'N-414') were included in the study. The mulches were applied at a rate of 2 t ha-1 before planting the winter crops. The Bt and non-Bt mulches differentially affected soil properties, weed dynamics and productivity of winter crops. The non-Bt mulches decreased the soil bulk density and penetration resistance, while increased the soil porosity. Wheat crop increased the soil porosity, pH, available N and soil organic matter content. Overall, non-Bt mulches improved the productivity of winter crops compared with Bt mulches. The toxins released by Bt mulches lowered the weed density; however, it negatively influenced soil properties (bulk density and available nitrogen) and productivity of winter crops. Therefore, appropriate crop rotation measures may be opted for the soils cultivated with Bt-cotton to conserve soil and achieve yield sustainability for the crops sown after cotton. Nonetheless, non-Bt mulches can be used for improving soil properties and productivity of winter crops.

Toxicological and biochemical analyses demonstrate no toxic effect of Bt maize on the Folsomia candida

The potential effects of Bt (Bacillus thuringiensis) maize on non-target organisms must be conducted before the Bt maize is commercially planted. Folsomia candida is one of the non-target organisms of Bt maize, also as an important indicator of soil quality and environmental pollution. In this study, a 90-day F. candida feeding test were conducted to evaluate the potential effects of two Bt maize lines IE09S034 and BT799 and their non-Bt conventional isolines Zong 31 and Zheng 58. The results show that Bt maize lines had no significant effects on the survival rate, reproduction, adult body length, larval body length, and the activities of acetyl cholinesterase, catalase and superoxide dismutase on the F. candida. Namely, Bt maize had no toxic effects on the F. candida.

Intercrops can mitigate pollen-mediated gene flow from transgenic cotton while simultaneously reducing pest densities

Genetically modified (GM) cotton, engineered to express Bt toxins that protect it from insect damage, has become the most successfully commercialized GM crop in China since its authorization in 1997. In light of the potential ecological consequences of pollen-mediated gene flow (PGF) from GM plants, a two year field trial was conducted to test the effects on PGF of sunflower, Helianthus annuus, buckwheat, Fagopyrum esculentum, and soybean, Glycine max, as intercrops in non-GM cotton fields during 2017 and 2018. DNA tests for hybridized seed were used to estimate rates of PGF in intercrop treatments. PGF was the lowest in cotton intercropped with either buckwheat or sunflower, likely due to the trapping of pollen in these flowers, and/or the diversion of pollinators away from cotton flowers. PGF declined as an exponential function of distance from the GM cotton; Y = -lnx was the model of best fit for estimating pollen dispersal potential. A sunflower intercrop reduced the peak abundance of Aphis gossypii, (Hemiptera: Aphididae), Bemisia tabaci (Hemiptera: Aleyrodidae), and Nysius ericae (Hemiptera: Lygaeidae) on cotton plants, although densities of Tetranychus cinnabarinus (Acari: Tetranychidae), were increased. A buckwheat intercrop had very similar effects on these pests, likely due to attraction of their natural enemies. We conclude that sunflower and buckwheat are suitable intercrops for reducing PGF from GM cotton, and may be useful for reducing PGF from other insect-pollinated GM crops in the agricultural landscape, while simultaneously contributing to control of specific pests. This is the first demonstration, to our knowledge, that intercrops can be used to reduce PGF from transgenic plants.

The effect of Bt Cry9Ee toxin on honey bee brood and adults reared in vitro, Apis mellifera (Hymenoptera: Apidae)

The effects of Bt Cry9Ee toxin on honey bee, Apis mellifera L., survival, developmental rate, larval weight, pollen consumption, and midgut bacterial diversity were tested in the laboratory. Honey bee larvae and adults were reared in vitro and fed a diet that contained Cry9Ee toxin at 0.01, 0.1, 1, and 10 mg/L. Cry9Ee toxin 0.01, 0.1, and 1 mg/L in diet used in this study may represent a value closer to field relevance and the highest concentration is unlikely to be encountered in the field and thus represent a worst case scenario. The dependent variables were compared for groups of honey bees feeding on treated diet and those feeding on negative control (no addition of a test substance), solvent control (0.01 mM Na₂CO₃), and positive control diet (dimethoate 45 mg/L). Bt Cry9Ee toxin did not affect survival or larval weight, and the result was great confidence in accepting the null hypothesis by power analysis. The effect on development rates and pollen consumption were the inconclusive results because the post-hoc power was less than 0.8. Furthermore, the midgut bacterial structure and compositions were determined using high-throughput sequencing targeting the V3-V4 regions of the 16S rDNA. All core honey bee intestinal bacterial class such as γ-Proteobacteria, Actinobacteria, α-Proteobacteria, Bacilli, β-Proteobacteria, and Bacteroidia were detected, and no significant changes were found in the species diversity and richness between Cry9Ee treatments and laboratory control.

Glyphosate is lethal and Cry toxins alter the development of the stingless bee Melipona quadrifasciata

Brazil is the second largest producer of genetically modified plants in the world. This agricultural practice exposes native pollinators to contact and ingestion of Bacillus thuringiensis proteins (e.g. Cry toxins) from transgenic plants. Furthermore, native bees are also exposed to various herbicides applied to crops, including glyphosate. Little is known about the possible effects of glyphosate and Cry proteins on stingless bees, especially regarding exposure at an immature stage. Here, we show for the first time that glyphosate is lethal, and that Cry toxins (Cry1F, Cry2Aa) alter the development of the stingless bee Melipona quadrifasciata upon contamination of larval food. Glyphosate was very toxic to the bee larvae, killing all of them within only a few days of exposure. Bees treated with Cry2Aa proteins had a higher survival rate and were delayed in their development, compared to the negative controls. Those treated with the Cry1F protein also suffered delays in their development, compared to the negative controls. In conclusion, the proteins Cry1F, Cry2Aa, and the herbicide glyphosate were highly toxic to the stingless bee M. quadrifasciata, causing lethal or sublethal effects which can severely impair colony growth and viability, and reduce pollination ability.

Pollen-mediated gene flow from transgenic cotton is constrained by physical isolation measures

The public concern about pollen-mediated gene flow (PGF) from genetically modified (GM) crops to non-GM crops heats up in recent years over China. In the current study, we conducted greenhouse and field experiments to measure PGF with various physical isolation measures, including 90, 80, 60 and 40 holes/cm² separation nets and Sorghum bicolor, Zea mays and Lycopersicon esculentum separation crops between GM cotton and non-GM line (Shiyuan321) by seed DNA test during 2013 to 2015, and pollen grain dyeing was also conducted to assess the pollen flow in greenhouse during 2013. Our results revealed that (1) PGF varied depending on the physical isolation measures. PGF was the lowest with 90 holes/cm² separation net and S. bicolor separation crop, and the highest with 40 holes/cm² separation net and no isolation measure. (2) Similar to PGF results, 90 holes/cm² separation net and S. bicolor separation crop could minimize the pollen dispersal. (3) PGF declined exponentially with increasing distance between GM cotton and Shiyuan321. Because of the production mode of farm household (limited cultivated area) in China, our study is particularly important, which is not only benefit for constraining PGF, but also has potential application value in practical production and the scientific researches.

Effects of Bt cabbage pollen on the honeybee Apis mellifera L

Honeybees may be exposed to insecticidal proteins from transgenic plants via pollen during their foraging activity. Assessing effects of such exposures on honeybees is an essential part of the risk assessment process for transgenic Bacillus thuringiensis (Bt) cabbage. Feeding trials were conducted in a laboratory setting to test for possible effects of Cry1Ba3 cabbage pollen on Italian-derived honeybees Apis mellifera L. Newly emerged A. mellifera were fed transgenic pollen, activated Cry1Ba3 toxin, pure sugar syrup (60% w/v sucrose solution), and non-transgenic cabbage pollen, respectively. Then the effects on survival, pollen consumption, weight, detoxification enzyme activity and midgut enzyme activity of A. mellifera were monitored. The results showed that there were no significant differences in survival, pollen consumption, weight, detoxification enzyme activity among all treatments. No significant differences in the activities of total proteolytic enzyme, active alkaline trypsin-like enzyme and weak alkaline trypsin-like enzyme were observed among all treatments. These results indicate that the side-effects of the Cry1Ba3 cabbage pollen on A. mellifera L. are unlikely.

Bt Cry1Ie Toxin Does Not Impact the Survival and Pollen Consumption of Chinese Honey Bees, Apis cerana cerana (Hymenoptera, Apidae)

The cry1Ie gene may be a good candidate for the development of Bt maize because over-expression of Cry1Ie is highly toxic to Lepidopteran pests such as Heliothis armigera Hübner and Ostrinia furnacalis Guenée. The Bt cry1Ie gene also has no cross resistance with other insecticidal proteins such as Cry1Ab, Cry1Ac, Cry1Ah, or Cry1F. Chinese honey bees (Apis cerana cerana) are potentially exposed to insect-resistant genetically modified (IRGM) crops expressing Cry1Ie toxin via the collection of IRGM crop pollen. In this study, we tested whether Chinese honey bee workers are negatively affected by sugar syrup containing 20, 200, or 20,000 ng/ml Cry1Ie toxin and 48 ng/ml imidacloprid under controlled laboratory conditions. Our results demonstrated that the Cry1Ie toxin does not adversely impact survival and pollen consumption of Chinese honey bees. However, imidacloprid decreases Chinese honey bee survival and the total pollen consumption on the 5th, 6th, and 18th d of exposure. The described bioassay is suitable to assess the effects of GM expressed toxins against honey bee.

Assessing Potential Impact of Bt Eggplants on Non-Target Arthropods in the Philippines

Studies on potential adverse effects of genetically engineered crops are part of an environmental risk assessment that is required prior to the commercial release of these crops. Of particular concern are non-target organisms (NTOs) that provide important ecosystem services. Here, we report on studies conducted in the Philippines over three cropping seasons with Bt eggplants expressing Cry1Ac for control of the eggplant fruit and shoot borer (EFSB), Leucinodes orbonalis, to examine potential effects on field abundance, community composition, structure and biodiversity of NTO’s, particularly non-target arthropod (NTA) communities. We document that many arthropod taxa are associated with Bt eggplants and their non-Bt comparators and that the number of taxa and their densities varied within season and across trials. However, we found few significant differences in seasonal mean densities of arthropod taxa between Bt and non-Bt eggplants. As expected, a lower abundance of lepidopteran pests was detected in Bt eggplants. Higher abundance of a few non-target herbivores was detected in non-Bt eggplants as were a few non-target beneficials that might control them. Principal Response Curve (PRC) analyses showed no statistically significant impact of Bt eggplants on overall arthropod communities through time in any season. Furthermore, we found no significant adverse impacts of Bt eggplants on species abundance, diversity and community dynamics, particularly for beneficial NTAs. These results support our previous studies documenting that Bt eggplants can effectively and selectively control the main pest of eggplant in Asia, the EFSB. The present study adds that it can do so without adverse effects on NTAs. Thus, Bt eggplants can be a foundational component for controlling EFSB in an Integrated Pest Management (IPM) program and dramatically reduce dependence on conventional insecticides.

Hematotoxicity and genotoxicity evaluations in Swiss mice intraperitoneally exposed to Bacillus thuringiensis (var kurstaki) spore crystals genetically modified to express individually Cry1Aa, Cry1Ab, Cry1Ac, or Cry2Aa

Bacillus thuringiensis (Bt) has been widely used in foliar sprays as part of integrated pest management strategies against insect pests of agricultural crops. Since the advent of genetically modified plants expressing Bt δ-endotoxins, the bioavailability of Cry proteins has increased, and therefore for biosafety reasons their adverse effects should be studied, mainly for nontarget organisms. We evaluated, in Swiss mice, the hematotoxicity and genotoxicity of the genetically modified strains of Bt spore crystals Cry1Aa, 1Ab, 1Ac, or 2Aa at 27 mg/kg, and Cry1Aa, 1Ab and 2Aa also at 136 and 270 mg/kg, administered with a single intraperitoneal injection 24 h before euthanasia. Controls received filtered water or cyclophosphamide. Blood samples collected by cardiac puncture were used to perform hemogram, and bone marrow was extracted for the micronucleus test. Bt spore crystals presented toxicity for lymphocytes when in higher doses, which varied according to the type of spore crystal studied, besides promoting cytotoxic and genotoxic effects for the erythroid lineage of bone marrow, mainly at highest doses. Although the profile of such adverse side effects can be related to their high level of exposure, which is not commonly found in the environment, results indicated that these Bt spore crystals were not harmless to mice. This suggests that a more specific approach should be taken to increase knowledge about their toxicological properties and to establish the toxicological risks to nontarget organisms. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 970-978, 2016.

Bt Toxin Cry1Ie Causes No Negative Effects on Survival, Pollen Consumption, or Olfactory Learning in Worker Honey Bees (Hymenoptera: Apidae)

The honey bee ( Apis mellifera L.) is a key nontarget insect in environmental risk assessments of insect-resistant genetically modified crops. In controlled laboratory conditions, we evaluated the potential effects of Cry1Ie toxin on survival, pollen consumption, and olfactory learning of young adult honey bees. We exposed worker bees to syrup containing 20, 200, or 20,000 ng/ml Cry1Ie toxin, and also exposed some bees to 48 ng/ml imidacloprid as a positive control for exposure to a sublethal concentration of a toxic product. Results suggested that Cry1Ie toxin carries no risk to survival, pollen consumption, or learning capabilities of young adult honey bees. However, during oral exposure to the imidacloprid treatments, honey bee learning behavior was affected and bees consumed significantly less pollen than the control and Cry1Ie groups.

Pollen-mediated gene flow from transgenic cotton under greenhouse conditions is dependent on different pollinators

With the large-scale release of genetically modified (GM) crops, there are ecological concerns on transgene movement from GM crops to non-GM counterparts and wild relatives. In this research, we conducted greenhouse experiments to measure pollen-mediated gene flow (PGF) in the absence and presence of pollinators (Bombus ignitus, Apis mellifera and Pieris rapae) in one GM cotton (resistant to the insect Helicoverpa armigera and the herbicide glyphosate) and two non-GM lines (Shiyuan321 and Hai7124) during 2012 and 2013. Our results revealed that: (1) PGF varied depending on the pollinator species, and was highest with B. ignitus (10.83%) and lowest with P. rapae (2.71%); (2) PGF with B. ignitus depended on the distance between GM and non-GM cottons; (3) total PGF to Shiyuan321 (8.61%) was higher than to Hai7124 (4.10%). To confirm gene flow, we tested hybrids carrying transgenes for their resistance to glyphosate and H. armigera, and most hybrids showed strong resistance to the herbicide and insect. Our research confirmed that PGF depended on pollinator species, distance between plants and the receptor plant.

Toxicological and biochemical analyses demonstrate no toxic effect of Cry1C and Cry2A to Folsomia candida

Collembolans are common soil arthropods that may be exposed to insecticidal proteins produced in genetically engineered (GE) plants by ingestion of crop residues or root exudates. In the present study, a dietary exposure assay was validated and used to assess the lethal and sublethal effects of two Bacillus thuringiensis (Bt) insecticidal proteins, Cry1C and Cry2A, on Folsomia candida. Using the insecticidal compounds potassium arsenate (PA), protease inhibitor (E-64), and Galanthus nivalis agglutinin (GNA) mixed into Baker's yeast, we show that the assay used can detect adverse effects on F. candida. Survival and development were significantly reduced when F. candida was fed a diet containing PA, E-64, and GNA at 9, 75, and 100 μg/g diet, respectively, but not when fed a diet containing 300 μg/g Cry1C or 600 μg/g Cry2A. The activities of test antioxidant-, detoxification-, and digestion-related enzymes in F. candida were unaltered by a diet containing 300 μg/g Cry1C or 600 μg/g Cry2A, but were significantly increased by a diet containing 75 μg/g E-64. The results confirm that Cry1C and Cry2A are not toxic to F. candida at concentrations that are much higher than those encountered under field conditions.

Ecological turmoil in evolutionary dynamics of plant-insect interactions: defense to offence

Available history manifests contemporary diversity that exists in plant-insect interactions. A radical thinking is necessary for developing strategies that can co-opt natural insect-plant mutualism, ecology and environmental safety for crop protection since current agricultural practices can reduce species richness and evenness. The global environmental changes, such as increased temperature, CO₂ and ozone levels, biological invasions, land-use change and habitat fragmentation together play a significant role in re-shaping the plant-insect multi-trophic interactions. Diverse natural products need to be studied and explored for their biological functions as insect pest control agents. In order to assure the success of an integrated pest management strategy, human activities need to be harmonized to minimize the global climate changes. Plant-insect interaction is one of the most primitive and co-evolved associations, often influenced by surrounding changes. In this review, we account the persistence and evolution of plant-insect interactions, with particular focus on the effect of climate change and human interference on these interactions. Plants and insects have been maintaining their existence through a mutual service-resource relationship while defending themselves. We provide a comprehensive catalog of various defense strategies employed by the plants and/or insects. Furthermore, several important factors such as accelerated diversification, imbalance in the mutualism, and chemical arms race between plants and insects as indirect consequences of human practices are highlighted. Inappropriate implementation of several modern agricultural practices has resulted in (i) endangered mutualisms, (ii) pest status and resistance in insects and (iii) ecological instability. Moreover, altered environmental conditions eventually triggered the resetting of plant-insect interactions. Hence, multitrophic approaches that can harmonize human activities and minimize their interference in native plant-insect interactions are needed to maintain natural balance between the existence of plants and insects.

Comparing Gene Expression Profiles Between Bt and non-Bt Rice in Response to Brown Planthopper Infestation

Bt proteins are the most widely used insecticidal proteins in transgenic crops for improving insect resistance. We previously observed longer nymphal developmental duration and lower fecundity in brown planthopper (BPH) fed on Bt rice line KMD2, although Bt insecticidal protein Cry1Ab could rarely concentrate in this non-target rice pest. In the present study, we performed microarray analysis in an effort to detect Bt-independent variation, which might render Bt rice more defensive and/or less nutritious to BPH. We detected 3834 and 3273 differentially expressed probe-sets in response to BPH infestation in non-Bt parent Xiushui 11 and Bt rice KMD2, respectively, only 439 of which showed significant differences in expression between rice lines. Our analysis revealed a shift from growth to defense responses in response to BPH infestation, which was also detected in many other studies of plants suffering biotic and abiotic stresses. Chlorophyll biosynthesis and basic metabolism pathways were inhibited in response to infestation. IAA and GA levels decreased as a result of the repression of biosynthesis-related genes or the induction of inactivation-related genes. In accordance with these observations, a number of IAA-, GA-, BR-signaling genes were downregulated in response to BPH. Thus, the growth of rice plants under BPH attack was reduced and defense related hormone signaling like JA, SA and ET were activated. In addition, growth-related hormone signaling pathways, such as GA, BR, and auxin signaling pathways, as well as ABA, were also found to be involved in BPH-induced defense. On the other side, 51 probe-sets (represented 50 genes) that most likely contribute to the impact of Bt rice on BPH were identified, including three early nodulin genes, four lipid metabolic genes, 14 stress response genes, three TF genes and genes with other functions. Two transcription factor genes, bHLH and MYB, together with lipid transfer protein genes LTPL65 and early nodulin gene ENOD93, are the most likely candidates for improving herbivore resistance in plants.

Evaluation of cytotoxic and antimicrobial effects of two Bt Cry proteins on a GMO safety perspective

Studies have contested the innocuousness of Bacillus thuringiensis (Bt) Cry proteins to mammalian cells as well as to mammals microbiota. Thus, this study aimed to evaluate the cytotoxic and antimicrobial effects of two Cry proteins, Cry8Ka5 (a novel mutant protein) and Cry1Ac (a widely distributed protein in GM crops). Evaluation of cyto- and genotoxicity in human lymphocytes was performed as well as hemolytic activity coupled with cellular membrane topography analysis in mammal erythrocytes. Effects of Cry8Ka5 and Cry1Ac upon Artemia sp. nauplii and upon bacteria and yeast growth were assessed. The toxins caused no significant effects on the viability (IC₅₀ > 1,000 µg/mL) or to the cellular DNA integrity of lymphocytes (no effects at 1,000 µg/mL). The Cry8Ka5 and Cry1Ac proteins did not cause severe damage to erythrocytes, neither with hemolysis (IC₅₀ > 1,000 µg/mL) nor with alterations in the membrane. Likewise, the Cry8Ka5 and Cry1Ac proteins presented high LC₅₀ (755.11 and >1,000 µg/mL, resp.) on the brine shrimp lethality assay and showed no growth inhibition of the microorganisms tested (MIC > 1,000 µg/mL). This study contributed with valuable information on the effects of Cry8Ka5 and Cry1Ac proteins on nontarget organisms, which reinforce their potential for safe biotechnological applications.

QTL affecting fitness of hybrids between wild and cultivated soybeans in experimental fields

The objective of this study was to identify quantitative trait loci (QTL) affecting fitness of hybrids between wild soybean (Glycine soja) and cultivated soybean (Glycine max). Seed dormancy and seed number, both of which are important for fitness, were evaluated by testing artificial hybrids of G. soja × G. max in a multiple-site field trial. Generally, the fitness of the F₁ hybrids and hybrid derivatives from self-pollination was lower than that of G. soja due to loss of seed dormancy, whereas the fitness of hybrid derivatives with higher proportions of G. soja genetic background was comparable with that of G. soja. These differences were genetically dissected into QTL for each population. Three QTLs for seed dormancy and one QTL for total seed number were detected in the F₂ progenies of two diverse cross combinations. At those four QTLs, the G. max alleles reduced seed number and severely reduced seed survival during the winter, suggesting that major genes acquired during soybean adaptation to cultivation have a selective disadvantage in natural habitats. In progenies with a higher proportion of G. soja genetic background, the genetic effects of the G. max alleles were not expressed as phenotypes because the G. soja alleles were dominant over the G. max alleles. Considering the highly inbreeding nature of these species, most hybrid derivatives would disappear quickly in early self-pollinating generations in natural habitats because of the low fitness of plants carrying G. max alleles.

Survival and development of a stored-product pest, Sitophilus zeamais (Coleoptera: Curculionidae), and its natural enemy, the parasitoid Lariophagus distinguendus (Hymenoptera: Pteromalidae), on transgenic Bt maize

BACKGROUND

The effect of transgenic maize (Zea mays L.) containing a lepidopteran-specific Bt toxin on a stored-product pest, Sitophilus zeamais Motschulsky, and its parasitoid, Lariophagus distinguendus Förster, was examined in the laboratory to test the impact of transgenic maize on stored-product pests and their biological control.

RESULTS

Weevils were not harmfully affected by transgenic Bt maize in their development characteristics (development time, body mass), and females emerging from transgenic maize kernels were larger. However, significantly fewer parasitoid females emerged from weevils that developed in transgenic kernels, although parasitoids did not develop more slowly and were not different in size or mass from their conspecifics emerging from hosts in non-transgenic maize kernels.

CONCLUSION

The emergence of female parasitoids was reduced in transgenic Bt maize, and this effect cannot be explained by the known lepidopteran-specific toxicity of Bt Cry1Ab toxin.

Impact of six transgenic Bacillus thuringiensis rice lines on four nontarget thrips species attacking rice panicles in the paddy field

As a key component of ecological risk assessments, nontarget effects of Bacillus thuringiensis (Bt) rice have been tested under laboratory and field conditions for various organisms. A 2-yr field experiment was conducted to observe the nontarget effects of six transgenic rice lines (expressing the Cry1Ab or fused protein of Cry1Ab and Cry1Ac) on four nontarget thrips species including Frankliniella intonsa (Trybom), F. tenuicornis (Uzel), Haplothrips aculeatus (F.), and H. tritici (Kurd), as compared with their rice parental control lines. Two sampling methods including the beat plate and plastic bag method were used to monitor the population densities of the four thrips species for 2 yr. The results showed that the seasonal average densities of four tested thrips species in Bt rice plots were significantly lower than or very similar to those in the non-Bt rice plots depending on rice genotypes, sampling methods, and years. Among all six tested Bt rice lines, transgenic B1 and KMD2 lines suppressed the population of these tested thrips species the most. Our results indicate that the tested Bt rice lines are unlikely to result in high population pressure of thrips species in comparison with non-Bt rice. In some cases, Bt rice lines could significantly suppress thrips populations in the rice ecosystem. In addition, compatibility of Bt rice, with rice host plant resistance to nontarget sucking pests is also discussed within an overall integrated pest management program for rice.

Effects of transgenic Bt cotton on soil fertility and biology under field conditions in subtropical inceptisol

Although there is large-scale adoption of Bt cotton by the farmers because of immediate financial gain, there is concern that Bt crops release Bt toxins into the soil environment which reduces soil chemical and biological activities. However, the majorities of such studies were mainly performed under pot experiments, relatively little research has examined the direct and indirect effects of associated cover crop of peanut with fertilization by combined application of organic and inorganic sources of nitrogen under field conditions. We compared soil chemical and biological parameters of Bt cotton with pure crop of peanut to arrive on a valid conclusion. Significantly higher dehydrogenase enzyme activity and KMnO(4)-N content of soil were observed in Bt cotton with cover crop of peanut over pure Bt cotton followed by pure peanut at all the crop growth stages. However, higher microbial population was maintained by pure peanut over intercropped Bt cotton, but these differences were related to the presence of high amount of KMnO(4)-N content of soil. By growing cover crop of peanut between Bt cotton rows, bacteria, fungi, and actinomycetes population increased by 60%, 14%, and 10%, respectively, over Bt cotton alone. Bt cotton fertilized by combined application of urea and farm yard manure (FYM) maintained higher dehydrogenase enzyme activity, KMnO(4)-N content of soil and microbial population over urea alone. Significant positive correlations were observed for dry matter accumulation, dehydrogenase enzyme activity, KMnO(4)-N content, and microbial population of soil of Bt cotton, which indicates no harmful effects of Bt cotton on soil biological parameters and associated cover crop. Our results suggest that inclusion of cover crop of peanut and FYM in Bt cotton enhanced soil chemical and biological parameters which can mask any negative effect of the Bt toxin on microbial activity and thus on enzymatic activities.

Effects of Cry1Ab transgenic maize on lifecycle and biomarker responses of the earthworm, Eisenia andrei

A 28-day study was conducted to determine the effects of the Bacillus thuringiensis Cry1Ab toxin on the earthworm Eisenia andrei. Previously, investigations have been limited to life-cycle level effects of this protein on earthworms, and mostly on E. fetida. In this study several endpoints were compared which included biomass changes, cocoon production, hatching success, a cellular metal-stress biomarker (Neutral Red Retention Time; NRRT) and potential genotoxic effects in terms of Randomly Amplified Polymorphic DNA sequences (RAPDs). NRRT results indicated no differences between treatments (p > 0.36), and NRRT remained the same for both treatments at different times during the experiment (p = 0.18). Likewise, no significant differences were found for cocoon production (p = 0.32) or hatching success (p = 0.29). Conversely, biomass data indicated a significant difference between the control treatment and the Bt treatment from the second week onwards (p < 0.001), with the Bt treatment losing significantly more weight than the isoline treatment. Possible confounding factors were identified that might have affected the differences in weight loss between groups. From the RAPD profiles no conclusive data were obtained that could link observed genetic variation to exposure of E. andrei to Cry1Ab proteins produced by Bt maize.

Toxicity intraperitoneal and intragastric route of Bacillus thuringiensis and Melia azedarach in mice

The aim of this investigation was the assessment of toxicity of two new isolates of Bacillus thuringiensis, and the aqueous extract of Melia azedarach through in vivo assays in CF1 mice. Bt 1958-2, Bt 2014-2 and the BTh Thuricide 63 standard isolates were grown in liquid usual glicosed medium, and Cry proteins were purified by centrifugation on a sucrose gradient. The supernatant was autoclaved at 121º C, 15min. to maintain the exotoxins. Dehydrated leaves of M. azedarach were used to prepare a 10% aqueous extract. Mice were treated either orally or intraperitoneally with a whole bacterial suspension (1.10(10) UFC/mL), a culture supernatant or purified crystal protein (50 µg/mL), and with the plant extract (50 µg/mL). The stomachs of the mice were collected and observed in stereomicroscopy, and the stomach contents were analyzed in 10% SDS-PAGE. Results showed that none of the oral treatments were toxic to mice, but intraperitoneal bacterial suspensions were lethal to the animals 6 - 24 hours after injection. In conclusion, the Cry proteins of the new B. thuringiensis isolates must be evaluated for their use as tools in the biotechnology field, since they do not show toxicity against mammals, intragastrically or peritoneally, just like the M. azedarach aqueous extract (10%), with those being indicated for the biological control of pest insects.

Impacts of Bt transgenic cotton on integrated pest management

Transgenic cotton that produced one or more insecticidal proteins of Bacillus thuringiensis (Bt) was planted on over 15 million hectares in 11 countries in 2009 and has contributed to a reduction of over 140 million kilograms of insecticide active ingredient between 1996 and 2008. As a highly selective form of host plant resistance, Bt cotton effectively controls a number of key lepidopteran pests and has become a cornerstone in overall integrated pest management (IPM). Bt cotton has led to large reductions in the abundance of targeted pests and benefited non-Bt cotton adopters and even producers of other crops affected by polyphagous target pests. Reductions in insecticide use have enhanced biological control, which has contributed to significant suppression of other key and sporadic pests in cotton. Although reductions in insecticide use in some regions have elevated the importance of several pest groups, most of these emerging problems can be effectively solved through an IPM approach.

Ecological trade-offs between jasmonic acid-dependent direct and indirect plant defences in tritrophic interactions

Recent studies on plants genetically modified in jasmonic acid (JA) signalling support the hypothesis that the jasmonate family of oxylipins plays an important role in mediating direct and indirect plant defences. However, the interaction of two modes of defence in tritrophic systems is largely unknown. In this study, we examined the preference and performance of a herbivorous leafminer (Liriomyza huidobrensis) and its parasitic wasp (Opius dissitus) on three tomato genotypes: a wild-type (WT) plant, a JA biosynthesis (spr2) mutant, and a JA-overexpression 35S::prosys plant. Their proteinase inhibitor production and volatile emission were used as direct and indirect defence factors to evaluate the responses of leafminers and parasitoids. Here, we show that although spr2 mutant plants are compromised in direct defence against the larval leafminers and in attracting parasitoids, they are less attractive to adult flies compared with WT plants. Moreover, in comparison to other genotypes, the 35S::prosys plant displays greater direct and constitutive indirect defences, but reduced success of parasitism by parasitoids. Taken together, these results suggest that there are distinguished ecological trade-offs between JA-dependent direct and indirect defences in genetically modified plants whose fitness should be assessed in tritrophic systems and under natural conditions.

Quantification of toxins in a Cry1Ac + CpTI cotton cultivar and its potential effects on the honey bee Apis mellifera L

Transgenic Cry1Ac + CpTI cotton (CCRI41) is increasingly planted throughout China. However, negative effects of this cultivar on the honey bee Apis mellifera L., the most important pollinator for cultivated ecosystem, remained poorly investigated. The objective of our study was to evaluate the potential side effects of transgenic Cry1Ac + CpTI pollen from cotton on young adult honey bees A. mellifera L. Two points emphasized the significance of our study: (1) A higher expression level of insecticidal protein Cry1Ac in pollen tissues was detected (when compared with previous reports). In particular, Cry1Ac protein was detected at 300 ± 4.52 ng g(-1) [part per billion (ppb)] in pollen collected in July, (2) Effects on chronic mortality and feeding behaviour in honey bees were evaluated using a no-choice dietary feeding protocol with treated pollen, which guarantee the highest exposure level to bees potentially occurring in natural conditions (worst case scenario). Tests were also conducted using imidacloprid-treated pollen at a concentration of 48 ppb as positive control for sublethal effect on feeding behaviour. Our results suggested that Cry1Ac + CpTI pollen carried no lethal risk for honey bees. However, during a 7-day oral exposure to the various treatments (transgenic, imidacloprid-treated and control), honey bee feeding behaviour was disturbed and bees consumed significantly less CCRI41 cotton pollen than in the control group in which bees were exposed to conventional cotton pollen. It may indicate an antifeedant effect of CCRI41 pollen on honey bees and thus bees may be at risk because of large areas are planted with transgenic Bt cotton in China. This is the first report suggesting a potential sublethal effect of CCRI41 cotton pollen on honey bees. The implications of the results are discussed in terms of risk assessment for bees as well as for directions of future work involving risk assessment of CCRI41 cotton.

Attraction of the parasitoid Cotesia marginiventris to host (Spodoptera frugiperda) frass is affected by transgenic maize

We assessed in the laboratory the attraction of the parasitoid Cotesia marginiventris (Cresson) toward odors emitted by conventional maize (Zea mays L. ssp. mays) and Bt (Bacillus thuringiensis) maize seedlings following actual or simulated injury by Spodoptera frugiperda (Smith), the parasitoid's host, and emitted by the host's frass, produced following consumption of conventional or Bt maize seedlings. Females of C. marginiventris exhibited similarly strong responses to conventional and Bt maize seedlings injured by the host or with simulated injury, and these were stronger than responses to clean air. In contrast, the responses of C. marginiventris females were consistently weaker toward host frass derived from Bt maize tissue compared to frass derived from conventional maize tissue. We hypothesized that the weakened response was due to a detrimental effect of Bt endotoxins, present in the Bt maize tissue, on the bacterial community present in the host's gut and frass, including bacteria that produce odors attractive to C. marginiventris. As an initial test of our hypothesis, we compared between the responses of C. marginiventris females to host frass produced following consumption of Bt maize and frass produced from conventional maize which had been treated with an antibiotic (tetracycline) to eliminate host gut bacteria. Our results showed that C. marginiventris females responded similarly weakly to host frass derived from conventional maize tissue treated with antibiotic and to frass derived from Bt maize tissue, treated or untreated with antibiotic, while they responded strongly to frass derived from conventional maize untreated with antibiotic, so provided initial, partial support for our hypothesis. We discussed the weakened response of C. marginiventris females to host frass derived from Bt maize in the context of plausible impacts of transgenic crop cultivars on parasitoid foraging and populations, and the implications for biological control of non-target, polyphagous pests, such as S. frugiperda.

Recombinant protease inhibitors for herbivore pest control: a multitrophic perspective

Protease inhibitors are a promising complement to Bt toxins for the development of insect-resistant transgenic crops, but their limited specificity against proteolytic enzymes and the ubiquity of protease-dependent processes in living organisms raise questions about their eventual non-target effects in agroecosystems. After a brief overview of the main factors driving the impacts of insect-resistant transgenic crops on non-target organisms, the possible effects of protease inhibitors are discussed from a multitrophic perspective, taking into account not only the target herbivore proteases but also the proteases of other organisms found along the trophic chain, including the plant itself. Major progress has been achieved in recent years towards the design of highly potent broad-spectrum inhibitors and the field deployment of protease inhibitor-expressing transgenic plants resistant to major herbivore pests. A thorough assessment of the current literature suggests that, whereas the non-specific inhibitory effects of recombinant protease inhibitors in plant food webs could often be negligible and their 'unintended' pleiotropic effects in planta of potential agronomic value, the innocuity of these proteins might always remain an issue to be assessed empirically, on a case-by-case basis.

Using existing data to predict and quantify the risks of GM forage to a population of a non-target invertebrate species: a New Zealand case study

Determining the effects of genetically modified (GM) crops on non-target organisms is essential as many non-target species provide important ecological functions. However, it is simply not possible to collect field data on more than a few potential non-target species present in the receiving environment of a GM crop. While risk assessment must be rigorous, new approaches are necessary to improve the efficiency of the process. Utilisation of published information and existing data on the phenology and population dynamics of test species in the field can be combined with limited amounts of experimental biosafety data to predict possible outcomes on species persistence. This paper presents an example of an approach where data from laboratory experiments and field studies on phenology are combined using predictive modelling. Using the New Zealand native weevil species Nicaeana cervina as a case study, we could predict that oviposition rates of the weevil feeding on a GM ryegrass could be reduced by up to 30% without threat to populations of the weevil in pastoral ecosystems. In addition, an experimentally established correlation between feeding level and oviposition led to the prediction that a consistent reduction in feeding of 50% or higher indicated a significant risk to the species and could potentially lead to local extinctions. This approach to biosafety risk assessment, maximising the use of pre-existing field and laboratory data on non-target species, can make an important contribution to informed decision-making by regulatory authorities and developers of new technologies.

Impact of Bacillus thuringiensis strains on survival, reproduction and foraging behaviour in bumblebees (Bombus terrestris)

BACKGROUND

Bacillus thuringiensis (Bt) and its protein crystals are used worldwide, either as a spray or when expressed in transgenic crops, for the control of pest insects. However, owing to their intensive use, there exists a debate regarding the involvement of this microbial insecticide in bee colony losses. In this study, in a tiered approach using laboratory microcolonies, an evaluation was made of the potential lethal and sublethal hazards on colony reproduction and foraging behaviour of workers of the bumblebee Bombus terrestris (L.) of two commercial Bt strains: kurstaki (Dipel) and aizawai (Xentari). Bumblebees, like honey bees, are intensively used in modern agriculture for pollination and fulfil a crucial role in the natural ecosystem.

RESULTS

Exposure of bumblebees dermally or via treated pollen to either of the two Bt formulations at their field recommended rates (0.1%) caused no reduction in survival. However, when applied in the feeding sugar water, aizawai killed all workers at a concentration of 0.1%, but this lethal effect was lost at 0.01%. With respect to reproductive effects, kurstaki was harmless, while aizawai at 0.1% delivered in the feeding sugar water and pollen reduced reproduction by 100 and 31% respectively. Lower doses of 0.01% aizawai in the sugar water showed no more effect. In addition, kurstaki at 0.1% and aizawai at 0.01% in the feeding sugar water did not impair the foraging behaviour, resulting in normal nest colony performance.

CONCLUSION

The results with kurstaki and aizawai demonstrated that, in general, the Bt strains are safe to B. terrestris bumblebees, although in some cases there were detrimental effects that depended on strain and route of exposure. In addition, the authors believe that to draw firm conclusions regarding the hazards of Bt to bumblebees would require more information on relevant concentrations of Bt products in the environment. Hence, routine testing for lethal and sublethal effects is recommended to ascertain combined use of Bt products and bumblebees in modern agriculture.

Impacts of six bt rice lines on nontarget rice feeding thrips under laboratory and field conditions

Nontarget impacts of six transgenic Bt rice lines (expressing the Cry1Ab or Cry1Ab/Cry1Ac protein) on the thrips, Stenchaetothrips biformis (Bagnall), attacking the rice seedling and tillering stages, were evaluated under laboratory and field conditions. Laboratory results showed relatively longer larval, pupal development and preoviposition durations of S. biformis. Although it had a shorter oviposition period, female adult longevity and less total laid eggs were found when fed on some tested Bt rice in comparison to non-Bt controls. S. biformis population dynamics in Bt and non-Bt plots were monitored using the plastic bag and beat plate methods. In the field, the temporal patterns of S. biformis population changes were similar between tested Bt rice lines and their respective control; however, the total number of S. biformis individuals collected from the Bt plots were significantly less or the same, varying from variety to variety, compared with those from the non-Bt plots. ELISA results showed that the Bt insecticidal protein could be transferred from Bt rice to the thrips, and the concentrations of the protein in rice leaves and thrips were not significantly correlated with some important biological parameters of the thrip. In addition, the potential effects of Bt rice on the abundance of S. biformis candidate predators are also discussed. In conclusion, our results show that the six Bt rice lines assessed may be less preferable host plants to S. biformis at the individual and population levels in comparison to the non-Bt rice plants.

Do genetically modified plants impact arbuscular mycorrhizal fungi?

The development and use of genetically modified plants (GMPs), as well as their ecological risks have been a topic of considerable public debate since they were first released in 1996. To date, no consistent conclusions have been drawn dealing with ecological risks on soil microorganisms of GMPs for the present incompatible empirical data. Arbuscular mycorrhizal fungi (AMF), important in regulating aboveground and underground processes in ecosystems, are the most crucial soil microbial community worthy of being monitored in ecological risks assessment of GMPs for their sensitivity to environmental alterations (plant, soil, climatic factor etc.). Based on current data, we suggest that there is a temporal-spatial relevance between expression and rhizosphere secretion of anti-disease and insecticidal proteins (e.g., Bt-Bacillus thuringiensis toxins) in and outer roots, and AMF intraradical and extraradical growth and development. Therefore, taking Bt transgenic plants (BTPs) for example, Bt insecticidal proteins constitutive expression and rhizosphere release during cultivation of BTPs may damage some critical steps of the AMF symbiotic development. More important, these processes of BTPs coincide with the entire life cycle of AMF annually, which may impact the diversity of AMF after long-term cultivation period. It is proposed that interactions between GMPs and AMF should be preferentially studied as an indicator for ecological impacts of GMPs on soil microbial communities. In this review, advances in impacts of GMPs on AMF and the effect mechanisms were summarized, highlighting the possible ecological implications of interactions between GMPs and AMF in soil ecosystems.

A case study for assessment of microbial community dynamics in genetically modified Bt cotton crop fields

Bt cotton was the first genetically modified crop approved for use in India. However, only a few studies have been conducted to assess the feasibility of its commercial application. Bt cotton is genetically modified to express a proteinaceous endotoxin (Cry) encoded by cry gene of Bacillus thuringiensis that has specific insecticidal activity against bollworms. Therefore, the amount of pesticides used for growing Bt cotton is postulated to be considerably low as compared to their non-Bt counterparts. Alternatively, it is also speculated that application of a genetically modified crop may alter the bio-geochemical balance of the agriculture field(s). Microbial community composition and dynamics is an important descriptor for assessment of such alterations. In the present study, we have assessed the culturable and non-culturable microbial diversities in Bt cotton and non-Bt cotton soils to determine the ecological consequences of application of Bt cotton. The analyses of microbial community structures indicated that cropping of Bt cotton did not adversely affect the diversity of the microbial communities.