Impact of Bt-corn MON88017 in comparison to three conventional lines on Trigonotylus caelestialium (Kirkaldy) (Heteroptera: Miridae) field densities

In Europe, Bt-corn resistant against the European Corn Borer has until now been the only genetically modified plant to be grown commercially. With the advent of the Western Corn Rootworm Bt-corn varieties with resistance against Coleoptera will become important. The cultivation of Bt-plants may have negative impacts on non-target organisms, i.e. all species not explicitly targeted by a given Bt-crop. One prominent non-target group in corn are the herbivorous plant bugs (Heteroptera: Miridae). They are common, abundant and exposed to the Cry-protein. We therefore assessed the potential impact of the cultivation of the Cry3Bb1-expressing Bt-corn variety MON88017 and three conventional varieties on this group. Trigonotylus caelestialium (Kirkaldy) was the most abundant plant bug at the experimental field. There was no evidence for a negative impact of MON88017 on this species, despite its considerable exposure to Cry3Bb1 demonstrated with ELISA. The conventional corn varieties, however, had a consistent and significant influence on the field densities of this species over all three growing seasons.     

Enhanced yield performance of <Emphasis Type="Italic">Bt</Emphasis> rice under target-insect attacks: implications for field insect management

The rapid development of transgenic biotechnology has greatly promoted the breeding of genetically engineered (GE) rice in China, and many GE rice lines are in the pipeline for commercialization. To understand field performances of GE rice, key agronomic traits of two insect-resistant Bt rice lines that have been granted biosafety certificates for commercial production in China were evaluated together with their nontransgenic counterparts under environmental conditions with significant differences in insect pressure. Results from the experiments showed enhanced field performances of the Bt GE rice lines compared with the non-GE counterparts for yield-related traits such as number of panicles and filled seeds per plant, under environmental conditions with no insecticide application. No detectable underlying cost of the Bt transgene was observed in the two insect-resistant GE rice lines, particularly in the GE hybrid rice line. Results further indicated significantly greater yield performances of the two insect-resistant GE rice lines under environmental conditions with non-target insect control compared with no insect control. It is concluded from this study that insect-resistant Bt GE rice, particularly the hybrid line, has great potential to maintain its high yield when ambient insect pressure is high. In addition, proper application of insecticides to control non-target insects will guarantee optimal performance of insect-resistant Bt GE rice.     

Development of a model system to assess the impact of genetically modified corn and aubergine plants on arbuscular mycorrhizal fungi

We developed an experimental model system to monitor the impact of generically modified (GM) plants on arbuscular mycorrhizal (AM) fungi, a group of non-target soil microorganisms, fundamental for soil fertility and plant nutrition. The system allowed us to study the effects of root exudates of both commercial Bt corn and aubergine plants expressing Dm-AMP1 defensin on different stages of the life cycle of the AM fungal species G. mosseae. Root exudates of Bt 176 corn significantly reduced pre-symbiotic hyphal growth, compared to Bt 11 and non-transgenic plants. No differences were found in mycelial growth in the presence of Dm-AMP1 and control plant root exudates. Differential hyphal morphogenesis occurred irrespective of the plant line, suggesting that both exuded Bt toxin and defensin do not interfere with fungal host recognition mechanisms. Bt 176 affected the regular development of appressoria, 36% of which failed to produce viable infection pegs. Our experimental model system represents an easy assay for testing the impact of GM plants on non-target soil-borne AM fungi.     

Transgenic Cry1Ab rice does not impact ecological fitness and predation of a generalist spider

Background

The commercial release of rice genetically engineered to express a Cry1Ab protein from Bacillus thuringiensis (Bt) for control of Lepidoptera in China is a subject of debate. One major point of the debate has focused on the ecological safety of Bt rice on nontarget organisms, especially predators and parasitoids that help control populations of insect pests.

Methodology/Principal Findings

A tritrophic bioassay was conducted to evaluate the potential impact of Cry1Ab-expressing rice on fitness parameters of a predaceous ground spider (Pardosa pseudoannulata (Bösenberg et Strand)) that had fed on Bt rice-fed brown planthopper (Nilaparvata lugens (Stål)) nymphs. Survival, development time and fecundity of this spider were not different when they were fed with Bt rice-fed or non-Bt rice-fed prey. Furthermore, ELISA and PCR gut assays, as well as a functional response trial, indicated that predation by P. pseudoannulata was not significantly different in Bt rice or non-Bt rice fields.

Conclusions/Significance

The transgenic Cry1Ab rice lines tested in this study had no adverse effects on the survival, developmental time and fecundity of P. pseudoannulata in the laboratory or on predation under field conditions. This suggests that this important predator would not be harmed if transgenic Cry1Ab rice were commercialized.     

基于根际与凋落物际评价转Bt水稻对土壤线虫群落的影响

转基因作物在商业化推广前,有必要评价其对非靶标土壤生物的生态影响。根系和凋落物与土壤的界面是代表植物直接影响土壤的两个典型活性微域,即根际和凋落物际。基于室内盆栽实验构建水稻根际和凋落物际,比较了这两个高活性微域中转Bt水稻克螟稻(KMD)与亲本水稻秀水11(XSD)对土壤可利用资源、微生物学性质和线虫群落的影响。结果表明:转Bt水稻对土壤性质的影响依赖于水稻生育期和微域的变化。与XSD相比,KMD在苗期和拔节期显著提高了凋落物际土壤可溶性有机氮含量(P0.05);在苗期显著降低了凋落物际土壤铵态氮含量,但在成熟期显著提高了凋落物际与交互微域土壤的铵态氮含量(P0.05)。与亲本水稻相比,转Bt水稻分别在苗期和成熟期显著提高了凋落物际土壤微生物生物量碳和活性,而在拔节期和成熟期显著降低了根际土壤微生物生物量氮含量(P0.05)。微域间的交互作用显著影响土壤微生物生物量、可溶性有机碳和氮、线虫总数和各食性线虫的数量(P0.05)。转Bt水稻总体上降低了土壤线虫总数,尤其在苗期和拔节期的凋落物际土壤中达到显著水平。重复测量方差分析表明转Bt水稻显著影响土壤食细菌(P0.01)和食真菌(P0.05)线虫数量,及线虫群落的通道指数和富集指数。水稻收获后KMD秸秆的Bt蛋白含量显著高于亲本,全部KMD处理的土壤样品中Bt蛋白含量无显著变化,因而转Bt水稻对土壤生物学性质的影响可能并非来源于Bt蛋白的作用,而更可能来自于水稻生长性状和凋落物性质的差异。     

Consumption of Bt Rice Pollen Containing Cry1C or Cry2A Protein Poses a Low to Negligible Risk to the Silkworm Bombyx mori (Lepidoptera: Bombyxidae)

By consuming mulberry leaves covered with pollen from nearby genetically engineered, insect-resistant rice lines producing Cry proteins derived from Bacillus thuringiensis (Bt), larvae of the domestic silkworm, Bombyx mori (Linnaeus) (Lepidoptera: Bombyxidae), could be exposed to insecticidal proteins. Laboratory experiments were conducted to assess the potential effects of Cry1C- or Cry2A-producing transgenic rice (T1C-19, T2A-1) pollen on B. mori fitness. In a short-term assay, B. mori larvae were fed mulberry leaves covered with different densities of pollen from Bt rice lines or their corresponding near isoline (control) for the first 3 d and then were fed mulberry leaves without pollen. No effect was detected on any life table parameter, even at 1800 pollen grains/cm² leaf, which is much higher than the mean natural density of rice pollen on leaves of mulberry trees near paddy fields. In a long-term assay, the larvae were fed Bt and control pollen in the same way but for their entire larval stage (approximately 27 d). Bt pollen densities ≥150 grains/cm² leaf reduced 14-d larval weight, increased larval development time, and reduced adult eclosion rate. ELISA analyses showed that 72.6% of the Cry protein was still detected in the pollen grains excreted with the feces. The low exposure of silkworm larvae to Cry proteins when feeding Bt rice pollen may be the explanation for the relatively low toxicity detected in the current study. Although the results demonstrate that B. mori larvae are sensitive to Cry1C and Cry2A proteins, the exposure levels that harmed the larvae in the current study are far greater than natural exposure levels. We therefore conclude that consumption of Bt rice pollen will pose a low to negligible risk to B. mori.     

Risk assessment system establishment for evaluating the potential impacts of imported Bacillus thuringiensis maize on a non-target insect,Tenebrio molitor

Large amounts of genetically modified grains producing Bacillus thuringiensis (Bt) toxins have been imported to Korea. Therefore, the establishment of a risk assessment system for evaluating the potential impacts of imported Bt maize on non-target insects is important. Before evaluating the environmental impacts of Bt grains of unknown origin, Cry protein types must first be identified in test Bt grains. Cry toxins of imported Bt maize grains were analyzed by ELISA. Because all tested Bt maize grains contained Cry1A, Tenebrio molitor, a non-lepidopteran species, was selected as the non-target insect species. A domestic maize strain that showed few differences in nutritional composition compared to the Bt maize grain was used as the alternative non-Bt control. Slightly increased survival rate and head capsule width of Bt maize-fed T. molitor were observed, indicating that Bt maize has no sub-chronic adverse effects on T. molitor. An ELISA test revealed that concentrations of Cry1A toxins slowly increased in the body of T. molitor when the insects were fed Bt maize. Such substantial amounts of Cry toxins remaining in the alimentary tract of larvae indicate that Cry toxins can be transferred to the higher trophic level of predatory insects. However, no Cry proteins were detected in the hemolymph of the Bt maize-fed larvae, suggesting that there is little possibility of Cry toxin exposure via T. molitor to the higher endoparasitoids. The risk assessment strategies and protocols established in this study may also be applicable to other imported Bt crops in Korea.     

Risk Assessment of Genetically Engineered Maize Resistant to Diabrotica spp.: Influence on Above-Ground Arthropods in the Czech Republic

Transgenic maize MON88017, expressing the Cry3Bb1 toxin from Bacillus thuringiensis (Bt maize), confers resistance to corn rootworms (Diabrotica spp.) and provides tolerance to the herbicide glyphosate. However, prior to commercialization, substantial assessment of potential effects on non-target organisms within agroecosystems is required. The MON88017 event was therefore evaluated under field conditions in Southern Bohemia in 2009–2011, to detect possible impacts on the above-ground arthropod species. The study compared MON88017, its near-isogenic non-Bt hybrid DK315 (treated or not treated with the soil insecticide Dursban 10G) and two non-Bt reference hybrids (KIPOUS and PR38N86). Each hybrid was grown on five 0.5 ha plots distributed in a 14-ha field with a Latin square design. Semiquantitative ELISA was used to verify Cry3Bb1 toxin levels in the Bt maize. The species spectrum of non-target invertebrates changed during seasons and was affected by weather conditions. The thrips Frankliniella occidentalis was the most abundant species in all three successive years. The next most common species were aphids Rhopalosiphum padi and Metopolophium dirhodum. Frequently observed predators included Orius spp. and several species within the Coccinellidae. Throughout the three-year study, analysis of variance indicated some significant differences (P<0.05). Multivariate analysis showed that the abundance and diversity of plant dwelling insects was similar in maize with the same genetic background, for both Bt (MON88017) and non-Bt (DK315) untreated or insecticide treated. KIPOUS and PR38N86 showed some differences in species abundance relative to the Bt maize and its near-isogenic hybrid. However, the effect of management regime on arthropod community was insignificant and accounted only for a negligible portion of the variability.     

Assessment of potential impacts due to unintentionally released Bt maize plants on non-target aphid Rhopalosiphum padi (Hemiptera: Aphididae)

Genetically modified maize crops expressing Bacillus thuringiensis (Bt) toxins (Bt maize) are increasingly cultivated worldwide, and large amounts of Bt maize have been imported to Korea. Before evaluating the environmental impacts of Bt maize of unknown origin on non-target insects, crystal (Cry) protein types in the imported Bt maize plants were identified. Because Cry1F was found in the tested Bt maize plants, Rhopalosiphum padi, a non-lepidopteran species, was selected as the non-target insect species. Additionally, a widely cultivated domestic maize strain was selected as an alternative control. No difference in survival rate, alata vivipara production, or host preference was observed between R. padi fed on the Bt maize and the control non-Bt maize, indicating that Bt maize plants had no sub-chronic adverse effects on R. padi. The average number of nymphs from Bt maize-fed aphids was 1.73-fold higher than that of non-Bt maize-fed aphids, implying that R. padi population density can increase after several generations in Bt maize fields. An enzyme-linked immunosorbent assay revealed that Cry1F toxin concentrations increased gradually in the body of R. padi when they were fed Bt maize, but that all ingested Cry toxins were excreted within 10 days after Bt-fed aphids were transferred to non-Bt maize, suggesting little possibility of Cry toxin exposure via R. padi to the endoparasitoids. However, the possibility still remains that Cry toxins can be transferred to predatory insects in higher trophic levels if they consume Bt maize-fed aphids.     

A Comprehensive Assessment of the Effects of Bt Cotton on Coleomegilla maculata Demonstrates No Detrimental Effects by Cry1Ac and Cry2Ab

The ladybird beetle, Coleomegilla maculata (DeGeer), is a common and abundant predator in many cropping systems. Its larvae and adults are predaceous, feeding on aphids, thrips, lepidopteran larvae and plant tissues, such as pollen. Therefore, this species is exposed to insecticidal proteins expressed in insect-resistant, genetically engineered cotton expressing Cry proteins derived from Bacillus thuringiensis (Bt). A tritrophic bioassay was conduced to evaluate the potential impact of Cry2Ab- and Cry1Ac-expressing cotton on fitness parameters of C. maculata using Bt-susceptible and -resistant larvae of Trichoplusia ni as prey. Coleomegilla maculata survival, development time, adult weight and fecundity were not different when they were fed with resistant T. ni larvae reared on either Bt or control cotton. To ensure that C. maculata were not sensitive to the tested Cry toxins independent from the plant background and to add certainty to the hazard assessment, C. maculata larvae were fed artificial diet incorporated with Cry2Ab, Cry1Ac or both at >10 times higher concentrations than in cotton tissue. Artificial diet containing E-64 was included as a positive control. No differences were detected in any life-table parameters between Cry protein-containing diet treatments and the control diet. In contrast, larvae of C. maculata fed the E-64 could not develop to the pupal stage and the 7-d larval weight was significantly negatively affected. In both feeding assays, the stability and bioactivity of Cry proteins in the food sources were confirmed by ELISA and sensitive-insect bioassays. Our results show that C. maculata is not affected by Bt cotton and is not sensitive to Cry2Ab and Cry1Ac at concentrations exceeding the levels in Bt cotton, thus demonstrating that Bt cotton will pose a negligible risk to C. maculata. More importantly, this study demonstrates a comprehensive system for assessing the risk of genetically modified plants on non-target organisms.     

Fungal chemical defence alters density‐dependent foraging behaviour and success in a fungivorous soil arthropod

1. Aggregative behaviour in fungivorous soil arthropods is widespread; its adaptive value, however, is largely unknown. In this study, the spatial foraging behaviour of a collembolan, Folsomia candida, and the fitness consequences of feeding at different densities on the filamentous fungus Aspergillus nidulans were investigated. The effect of two fungal strains were compared; a wild‐type (wt) and a transgenic strain that lacks the ability to express the global secondary metabolite regulator LaeA (ΔlaeA). 2. In laboratory foraging tests, F. candida exhibited aggregated distributions of individuals across four distinct fungal colonies that were arranged in short distances from each other. By quantifying the extent of the feeding damage at each single colony, a more evenly distributed feeding activity was found among wt colonies than among chemical‐deficient colonies. 3. In a fitness experiment, where collembolans at different densities were restricted to feed on single A. nidulans colonies, mean growth rate of F. candida was positively related to density on the wt A. nidulans strain, but negatively related to density on the chemical‐deficient strain. 4. Depending on the fungus' ability to express secondary chemicals and availability of fungal food sources, F. candida may employ different foraging strategies: (i) avoidance of prolonged feeding on single colonies in a rich habitat (travel costs low), and (ii) intensified group feeding on single colonies in a resource‐limited habitat (travel costs high). It was hypothesised that flexibility in fungivore foraging behaviour (clumping vs. spreading feeding activity) is adaptive because it allows avoidance/overcoming induced fungal chemical defence.     

Extrapolating non-target risk of Bt crops from laboratory to field

The tiered approach to assessing ecological risk of insect-resistant transgenic crops assumes that lower tier laboratory studies, which expose surrogate non-target organisms to high doses of insecticidal proteins, can detect harmful effects that might be manifested in the field. To test this assumption, we performed meta-analyses comparing results for non-target invertebrates exposed to Bacillus thuringiensis (Bt) Cry proteins in laboratory studies with results derived from independent field studies examining effects on the abundance of non-target invertebrates. For Lepidopteran-active Cry proteins, laboratory studies correctly predicted the reduced field abundance of non-target Lepidoptera. However, laboratory studies incorporating tri-trophic interactions of Bt plants, herbivores and parasitoids were better correlated with the decreased field abundance of parasitoids than were direct-exposure assays. For predators, laboratory tri-trophic studies predicted reduced abundances that were not realized in field studies and thus overestimated ecological risk. Exposure to Coleopteran-active Cry proteins did not significantly reduce the laboratory survival or field abundance of any functional group examined. Our findings support the assumption that laboratory studies of transgenic insecticidal crops show effects that are either consistent with, or more conservative than, those found in field studies, with the important caveat that laboratory studies should explore all ecologically relevant routes of exposure.     

Does Bt rice pose risks to non‐target arthropods? Results of a meta‐analysis in China

Transgenic Bt rice expressing the insecticidal proteins derived from Bacillus thuringiensis Berliner (Bt) has been developed since 1989. Their ecological risks towards non‐target organisms have been investigated; however, these studies were conducted individually, yielding uncertainty regarding potential agroecological risks associated with large‐scale deployment of Bt rice lines. Here, we developed a meta‐analysis of the existing literature to synthesize current knowledge of the impacts of Bt rice on functional arthropod guilds, including herbivores, predators, parasitoids and detritivores in laboratory and field studies. Laboratory results indicate Bt rice did not influence survival rate and developmental duration of herbivores, although exposure to Bt rice led to reduced egg laying, which correctly predicted their reduced abundance in Bt rice agroecosystems. Similarly, consuming prey exposed to Bt protein did not influence survival, development or fecundity of predators, indicating constant abundances of predators in Bt rice fields. Compared to control agroecosystems, parasitoid populations decreased slightly in Bt rice cropping systems, while detritivores increased. We draw two inferences. One, laboratory studies of Bt rice showing effects on ecological functional groups are mainly either consistent with or more conservative than results of field studies, and two, Bt rice will pose negligible risks to the non‐target functional guilds in future large‐scale Bt rice agroecosystems in China.     

Impact of ecological factors on the initial invasion of Bt transgenes into wild populations of birdseed rape (Brassica rapa)

The inevitable escape of transgenic pollen from cultivated fields will lead to the emergence of transgenic crop-wild plant hybrids in natural patches of wild plants. The fate of these hybrids and that of the transgene depend on their ability to compete with their wild relatives. Here we study ecological factors that may enhance the fitness of genetically modified hybrids relative to wild plants for a Bacillus thuringiensis (Bt) transgene conferring resistance to insects. Mixed stands of wild plants and first-generation hybrids were grown under different conditions of herbivore pressure and density, with Bt oilseed rape (Brassica napus) as the crop and B. rapa as the wild recipient. Biomass and fitness components were measured from plant germination to the germination of their offspring. The frequency of transgenic seedlings in the offspring generation was estimated using the green fluorescent protein marker. The biomass of F₁ Bt-transgenic hybrids relative to that of wild-type plants was found to be sensitive to both plant density and herbivore pressure, but herbivore pressure appeared as the major factor enhancing their relative fitnesses. In the absence of herbivore pressure, Bt hybrids produced 6.2-fold fewer seeds than their wild neighbors, and Bt plant frequency fell from 50% to 16% within a single generation. Under high herbivore pressure, Bt hybrids produced 1.4-fold more seeds, and Bt plant frequency was 42% in the offspring generation. We conclude that high-density patches of highly damaged wild plants are the most vulnerable to Bt-transgene invasion. They should be monitored early to detect potential transgene spread.     

Transgenic Cabbage Expressing Cry1Ac1 Does Not Affect the Survival and Growth of the Wolf Spider,Pardosa astrigera L. Koch (Araneae: Lycosidae)

Both herbivores that consume transgenic crops and their predators can be exposed to insecticidal proteins expressed in those crops. We conducted a tritrophic bioassay to evaluate the ecotoxicological impacts that Bt cabbage (Brassica oleracea var. capitata) expressing Cry1Ac1 protein might have on the wolf spider (Pardosa astrigera), a non-target generalist predator. Enzyme-Linked Immunosorbent Assays indicated that protein levels were 4.61 ng g^-1 dry weight in fruit flies (Drosophila melanogaster) fed with the transgenic cabbage and 1.86 ng g^-1 dry weight in the wolf spiders that preyed upon them. We also compared the life history traits of spiders collected from Bt versus non-Bt cabbage and found no significant differences in their growth, survival, and developmental rates. Because Bt cabbage did not affect the growth of fruit flies, we conclude that any indirect effects that this crop had on the wolf spider were probably not mediated by prey quality. Therefore, exposure to Cry1Ac1 protein when feeding upon prey containing that substance from transgenic cabbage has only a negligible influence on those non-target predatory spiders.     

Occurrence and field densities of Coleoptera in the maize herb layer: implications for Environmental Risk Assessment of genetically modified <Emphasis Type="Italic">Bt</Emphasis>-maize

Beetles (Coleoptera) are a diverse and ecologically important group of insects in agricultural systems. The Environmental Risk Assessment (ERA) of genetically modified Bt-crop varieties with insect resistances thus needs to consider and assess the potential negative impacts on non-target organisms belonging to this group. We analysed data gathered during 6 years of field-release experiments on the impact of two genetically modified Bt-maize varieties (Ostrinia-resistant MON810 and Diabrotica-resistant MON88017) on the occurrence and field densities of Coleoptera, especially the two families Coccinellidae and Chrysomelidae. Based on a statistical analysis aimed at establishing whether Bt-maize varieties are equivalent to their near-isogenic counterparts, we discuss the limitations of using field experiments to assess the effects of Bt-maize on these two beetle families. The densities of most of the beetle families recorded in the herb layer were very low in all growing seasons. Coccinellidae and Chrysomelidae were comparatively abundant and diverse, but still low in numbers. Based on their role as biological control agents, Coccinellidae should be a focus in the ERA of Bt-plants, but given the large natural variability in ladybird densities in the field, most questions need to be addressed in low-tier laboratory tests. Chrysomelidae should play a negligible role in the ERA of Bt-plants, since they occur on-crop as secondary pests only. Species occurring off-crop, however, can be addressed in a similar fashion as non-target Lepidoptera in Cry1Ab expressing Bt-maize.     

Bt和Bar基因转化对水稻不同组织生态位微生物群落组成及潜在功能影响

【目的】转Bt基因和Bar基因植物的微生态效应是环境安全评价的重要因素,但关于Bt基因和Bar基因转化引起的水稻基因型改变对水稻不同组织生态位微生物群落组成和潜在功能的影响还无系统研究。【方法】以转Bt基因和Bar基因水稻T1C-1及其亲本对照Minghui63为研究对象,基于细菌16S rRNA基因和真菌ITS高通量测序技术,分析抽穗期T1C-1和Minghui63根际土壤微生物以及根、茎、叶内生菌的群落结构和潜在功能。【结果】细菌和真菌群落多样性在水稻不同组织生态位之间发生显著变化,地下部分组织生态位(根际土壤和根系)微生物多样性显著高于地上部分(叶和茎)。T1C-1显著影响叶片内生真菌的香农指数和辛普森指数,而对茎和根的内生菌以及根际土壤微生物多样性无显著影响。叶片内生真菌曲霉菌属(Aspergillus)和篮状菌属(Talaromyces)相对丰度在T1C-1显著增加,推测其参与碳素代谢、能量代谢和转录作用酶合成等过程。T1C-1和Minghui63微生物群落关联网络分析表明,T1C-1的平均聚类系数和平均度显著高于Minghui63,因而T1C-1提高了相关微生物群落网络复杂程度。通过重建未观测状态对群落进行系统发育研究(phylogenetic investigation of communities by reconstruction of unobserved states, PICRUSt2),对叶片内生真菌功能酶基因进行功能预测,相对于Minghui63,T1C-1显著改变了碳素代谢、脂类代谢和能量代谢等途径。【结论】相较于根际土壤,叶片内生真菌的群落组成和潜在功能对T1C-1更敏感。尽管如此,T1C-1并未导致叶片内生真菌的多样性指数降低。为了更准确地评估转基因植物的微生态效应,我们需要加强对不同组织生态位内生菌多样性的关注。     

Does feeding on Bt-maize affect the slug Arion vulgaris (Mollusca: Arionidae)?

Via expression of Cry-proteins, toxic for specific insect groups, genetically modified Bacillus thuringiensis (Bt) maize offers an effective protection against insect pests. In a laboratory experiment with two transgenic and two non-transgenic maize varieties, a potential impact of Bt-maize was examined for the non-target slug Arion vulgaris. Lifetime after field collection, weight change and oviposition was examined for slugs fed with Bt-maize, non Bt-maize or dandelion (Taraxacum officinale). Test parameters were neither significantly different between transgenic and non-transgenic varieties nor among the maize varieties overall. Slugs fed with dandelion showed a significantly longer lifetime after field collection, gained significantly more weight and laid eggs. The results did not show a Bt-effect but indicated the general poor quality of maize as food resource for slugs.     

Decomposition of Bt transgenic rice residues and response of soil microbial community in rapeseed–rice cropping system

In this study, Bt transgenic rice (KMD rice) residue decomposition and the associated microbial community in a rapeseed–rice cropping system were assessed in comparison with its parental non-Bt rice variety (XiuShui 11). Decomposition was measured as mass loss by straw and root decay in litterbags over two consecutive years. Bacterial and fungal community compositions associated with residue decomposition were detected by terminal restriction fragment length polymorphism (T-RFLP) and the additive main effects multiplicative interaction (AMMI) analysis model. Decomposition dynamics and bacterial and fungal communities associated with decomposition were strongly affected by surface and incorporated placements, and by temporal factors. However, no significant differences were observed between Bt and non-Bt rice variety in either decomposition dynamics or in the soil microbial communities associated with residue decay. Our field study indicated that the insertion of the cry1Ab gene into Xiushui 11 rice genome had no significant effect on the residual decay and decomposition-associated microbial community compositions in the rapeseed-rice cropping system.     

Reduced Mythimna separata infestation on Bt corn could benefit aphids

Use of genetically engineered plants that express insecticidal Cry proteins derived from Bacillus thuringiensis (Bt) have been proven efficacious for managing lepidopteran pests. However, in some cases herbivores that are not targeted by the Bt trait have increased in importance. It has been suggested that reduced caterpillar damage to Bt crops could lead to decreased levels of induced plant defensive compounds which might benefit other non-target herbivores. Here we investigated the potential effect of reduced damage by larvae of Mythimna separata on aphid populations in Bt corn. We compared the performance of Rhopalosiphum maidis feeding on non-Bt corn plants that had been infested by M. separata larvae or were uninfested. The results showed that caterpillar-infested corn plants significantly reduced the fitness of R. maidis leading to a prolonged nymphal development time, reduced adult longevity and fecundity compared to uninfested plants. Consequently, the population growth rate of corn aphids feeding on caterpillar-infested corn plants was significantly lower than on uninfested plants. As expected, the aphids performed significantly better on Lepidoptera-resistant Bt corn than on non-Bt corn when plants were infested with M. separata, since the caterpillars caused very little damage to the Bt plants. The current findings indicate that reduced M. separata infestation could benefit aphid development in Bt corn. Bt corn has the potential to be commercialized in China in the near future and aphids and other non-target pests should be monitored in the farming fields.