Bt Maize Research Articles

Seven Years of Monitoring Susceptibility to Cry1Ab and Cry1F in Asian Corn Borer.

Resistance monitoring in the Asian corn borer, Ostrinia furnacalis, is necessary to accommodate the commercial introduction and stewardship of Bt maize in China. The susceptibility of 56 O. furnacalis field populations, collected between 2015 and 2021 from the corn belt regions of China, to Cry1Ab and Cry1F toxins was determined. Neonate larvae (within 12 h after hatching) were placed on the surface of semi-artificial agar-free diet incorporating a series of concentrations of purified toxins, and mortality was evaluated after 7d. The median lethal concentration (LC50) values of Cry1Ab and Cry1F were 0.05 to 0.37 µg/g (protein/diet) and 0.10 to 1.22 µg/g, respectively. Although interpopulation variation in susceptibility to the toxins was observed, the magnitude of the differences was 5.8-fold and 8.3-fold for Cry1Ab and Cry1F, respectively. These results suggested that the observed susceptibility differences reflect natural geographical variation in response and not variation caused by prior exposure to selection pressures. Therefore, the O. furnacalis populations were apparently still susceptible to Cry1Ab and Cry1F across their range within China. The monitoring data established here will serve as a comparative reference for early warning signs of field-evolved resistance after the cultivation of Bt maize in China.

Monitoring Insect Resistance to Bt Maize in the European Union: Update, Challenges, and Future Prospects.

Transgenic maize producing the Cry1Ab toxin of Bacillus thuringiensis (Bt maize) was approved for cultivation in the European Union (EU) in 1998 to control the corn borers Sesamia nonagrioides (Lefèbvre) and Ostrinia nubilalis (Hübner). In the EU since then, Cry1Ab is the only Bt toxin produced by Bt maize and Spain is the only country where Bt maize has been planted every year. In 2021, about 100,000 hectares of Bt maize producing Cry1Ab were cultivated in the EU, with Spain accounting for 96% and Portugal 4% of this area. In both countries, Bt maize represented less than 25% of all maize planted in 2021, with a maximum regional adoption of 64% Bt maize in northeastern Spain. Insect resistance management based on the high-dose/refuge strategy has been implemented in the EU since 1998. This has been accompanied by monitoring to enable early detection of resistance. The monitoring data from laboratory bioassays show no decrease in susceptibility to Cry1Ab had occurred in either pest as of 2021. Also, control failures have not been reported, confirming that Bt maize producing Cry1Ab remains effective against both pests. Conditions in the EU preventing approval of new genetically modified crops, including maize producing two or more Bt toxins targeting corn borers, may limit the future effectiveness of resistance management strategies.

Can Essential Oils Be a Natural Alternative for the Control of Spodoptera frugiperda? A Review of Toxicity Methods and Their Modes of Action

Spodoptera frugiperda is a major pest of maize crops. The application of synthetic insecticides and the use of Bt maize varieties are the principal strategies used for its control. However, due to the development of pesticide resistance and the negative impact of insecticides on the environment, natural alternatives are constantly being searched for. Accordingly, the objective of this review was to evaluate the use of essential oils (EOs) as natural alternatives for controlling S. frugiperda. This review article covers the composition of EOs, methods used for the evaluation of EO toxicity, EO effects, and their mode of action. Although the EOs of Ocimum basilicum, Piper marginatum, and Lippia alba are the most frequently used, Ageratum conyzoides, P. septuplinervium. O. gratissimum and Siparuna guianensis were shown to be the most effective. As the principal components of these EOs vary, then their mode of action on the pest could be different. The results of our analysis allowed us to evaluate and compare the potential of certain EOs for the control of this insect. In order to obtain comparable results when evaluating the toxicity of EOs on S. frugiperda, it is important that methodological issues are taken into account.

Bt maize can provide non-chemical pest control and enhance food safety in China.

China is the world's second-largest maize producer and consumer. In recent years, the invasive fall armyworm Spodoptera frugiperda (J.E. Smith) has adversely affected maize productivity and compromised food security. To mitigate pest-inflicted food shortages, China's Government issued biosafety certificates for two genetically modified (GM) Bt maize hybrids, Bt-Cry1Ab DBN9936 and Bt-Cry1Ab/Cry2Aj Ruifeng 125, in 2019. Here, we quantitatively assess the impact of both Bt maize hybrids on pest feeding damage, crop yield and food safety throughout China's maize belt. Without a need to resort to synthetic insecticides, Bt maize could mitigate lepidopteran pest pressure by 61.9-97.3%, avoid yield loss by 16.4-21.3% (range -11.9-99.2%) and lower mycotoxin contamination by 85.5-95.5% as compared to the prevailing non-Bt hybrids. Yield loss avoidance varied considerably between experimental sites and years, as mediated by on-site infestation pressure and pest identity. For either seed mixtures or block refuge arrangements, pest pressure was kept below established thresholds at 90% Bt maize coverage in Yunnan (where S. frugiperda was the dominant species) and 70% Bt maize coverage in other sites dominated by Helicoverpa armigera (Hübner) and Ostrinia furnacalis (Guenée). Drawing on experiences from other crop/pest systems, Bt maize in se can provide area-wide pest management and thus, contribute to a progressive phase-down of chemical pesticide use. Hence, when consciously paired with agroecological and biodiversity-based measures, GM insecticidal crops can ensure food and nutrition security, contribute to the sustainable intensification of China's agriculture and reduce food systems' environmental footprint.

High-Dose Assessment of Transgenic Insect-Resistant Maize Events against Major Lepidopteran Pests in China.

Lepidopteran pests present a key problem for maize production in China. In order to develop a new strategy for the pest control, the Chinese government has issued safety certificates for insect-resistant transgenic maize, but whether these transformation events can achieve high dose levels to major target pests is still unclear. In this paper, the transformation events of DBN9936 (Bt-Cry1Ab), DBN9936 × DBN9501 (Bt-Cry1Ab + Vip3A), Ruifeng 125 (Bt-Cry1Ab/Cry2Aj), and MIR162 (Bt-Vip3A) were planted in the Huang-huai-hai summer corn region of China to evaluate the lethal effects on major lepidopteran pests, Spodoptera frugiperda, Helicoverpa armigera, Ostrinia furnacalis, Conogethes punctiferalis, Mythimna separata, Leucania loreyi, and Athetis lepigone, using an artificial diet containing lyophilized Bt maize tissue at a concentration representing a 25-fold dilution of tissue. The results showed that the corrected mortalities of DBN9936 (Bt-Cry1Ab), DBN9936 × DBN9501 (Bt-Cry1Ab + Vip3A), Ruifeng 125 (Bt-Cry1Ab/Cry2Aj), and MIR162 (Bt-Vip3A) to the seven pests were in the ranges 53.80~100%, 62.98~100%, 57.09~100%, and 41.02~100%, respectively. In summary, the events of DBN9936, DBN9936 × DBN9501, and MIR162 reached high dose levels to S. frugiperda. DBN9936 × DBN9501 only at the R1 stage reached a high dose level to H. armigera. DBN9936, DBN9936 × DBN9501, and Ruifeng 125, at most growth stages, reached high dose levels to O. furnacalis, and these three events at some stages also reached high dose levels to A. lepigone. Ruifeng 125 presented a high dose level only to C. punctiferalis. However, no transformations reached high dose levels to either M. separata or L. loreyi. This study provides a support for the breeding of high-dose varieties to different target pests, the combined application of multiple genes and the commercial regional planting of insect-resistant transgenic maize in China.

Bt‐maize in neotropical arthropod food webs: community‐stress or lack thereof?

AbstractAlthough the agricultural use of genetically engineered (GE) plants has been employed extensively, its adoption is still controversial and its impact on arthropods has rarely been scrutinized at the community level. If this technology is aimed at a drastic reduction of a key community component, significant community‐level impact is expected and needs to be assessed. Thus, food web analysis was used to assess the short‐term impact of genetically modified maize plants, Zea mays L. (Poaceae), expressing insecticidal proteins of the bacterium Bacillus thuringiensis Berliner (i.e., Bt maize), on the associated arthropod assemblage in a neotropical scenario. Arthropods associated with winter and summer cultivations with Bt and non‐Bt (isoline) maize were thus sampled using sweep nets and whole‐plant collections throughout the plant phenological cycle. The collected information was used to build a plant‐consumer‐predator trivariate network based on data of individual arthropod body mass, numerical abundance, and biomass abundance using food web analysis. Eighty‐five arthropod species were sampled, and whereas cultivation season significantly affected arthropod species richness and abundance, only marginal differences existed between maize hybrids (Bt vs. non‐Bt). The recognized food webs also indicated significant differences between seasons. In contrast, Bt‐maize‐hosted food webs were similar to those of the non‐Bt isoline indicating no significant impact on arthropod food webs. Nonetheless, Bt maize did not provide significant control of the target pest species, the fall armyworm, nor did it lead to higher crop yield, raising questions about its current usefulness in the region.

Effects of Insect-Resistant Maize HGK60 on Community Diversity of Bacteria and Fungi in Rhizosphere Soil.

The influence of biotech crops on microbial communities in rhizosphere soil is an important issue in biosafety assessments. The transgenic maize HGK60 harboring the Bt cry1Ah gene enhanced the resistance to lepidopteran pests, while the ecological risk of HGK60 maize on rhizosphere microorganisms is unclear. In this study, we comprehensively analyzed the diversity and composition of bacterial and fungal communities in the rhizosphere soil around Bt maize HGK60 and the near-isogenic non-Bt maize ZD958 at four growth stages via a high-throughput sequencing technique. The results showed that HGK60 maize unleashed temporary effects on the bacterial and fungal diversity and richness during the study plant's development, which would be restored after one cycle of plant cultivation due to the application of the same agricultural management. The differences of bacterial and fungal communities were marked by seasonality, while the different growth stage was the important factor as opposed to the cultivar contributing to the shifts in the bacterial and fungal communities' structure. This study will provide useful information regarding the impact of Bt transgenic maize on the soil microbiome and a theoretical basis for the development of a safety assessment approach for Bt maize in China.

Selection, effective dominance, and completeness of Cry1A.105/Cry2Ab2 dual-protein resistance in Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae)

In the U.S., Helicoverpa zea (Boddie) is a major pest targeted by both transgenic maize and cotton expressing Bacillus thuringiensis (Bt) proteins. Resistance of insect to Bt maize and cotton containing cry1A and cry2A genes has widely occurred in the U.S. In this study, two trials were performed to investigate larval survival and development of a Cry1A.105/Cry2Ab2 dual-protein resistant (VT2P-RR), a susceptible, and an F1 heterozygous (VT2P-RS) populations of H. zea on ears of nine Bt and three non-Bt maize hybrids. The Bt maize hybrids evaluated represent five common pyramided traits expressing two or three of the Cry1A.105, Cry1Ab, Cry1F, Cry2Ab2, and Vip3Aa20 proteins. In the laboratory, neonates of the three H. zea populations were inoculated on silks of ears collected from maize at R1–R2 plant stages; and larval survivorship was checked 10 d after neonate release. All three insect populations survived normally on non-Bt maize ears. Varied numbers of VT2P-RR and VT2P-RS survived on ears of Cry1A.105/Cry2Ab2 maize, while all larvae of the three populations died or could not develop on ears of Vip3Aa20-expressing maize. The results demonstrated that the dual-protein resistant H. zea was not cross-resistant to Vip3Aa20-expressing maize, and thus traits with vip3Aa20 gene should be effective to manage Cry1A.105/Cry2Ab2-resistant H. zea. The resistance in VT2P-RR was determined to be incomplete on Cry1A.105/Cry2Ab2 maize. The effective dominance levels varied greatly, from recessive to incompletely dominant, depending on maize hybrids and trials, suggesting that proper selection of maize hybrids could be important for mitigating the Cry1A.105/Cry2Ab2 resistance. The data generated should aid in modeling multiple-protein Bt resistance in H. zea.

Inheritance of Resistance to Cry1A.105 in Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae).

Simple SummaryThe corn earworm, Helicoverpa zea (Boddie), is a target pest of Bacillus thuringiensis (Bt) cotton and maize in North America. This pest has evolved resistance to both Bt crops in the United States, which is a significant threat to their sustainable use for H. zea control. Cry1A.105 is a Bt toxin commonly used in commercial transgenic maize hybrids to control above-ground caterpillar pests, such as H. zea. The aim of this study is to describe the inheritance of Cry1A.105 resistance in H. zea. Genetic-cross studies revealed that the resistance to Cry1A.105 is controlled by a single, autosomal, nonrecessive gene. Data generated from the study will be useful in resistance risk assessment and refining Bt resistance mitigation programs for H. zea control.Cry1A.105 is a bioengineered Bacillus thuringiensis (Bt) insecticidal protein consisting of three domains derived from Cry1Ac, Cry1Ab, and Cry1F. It is one of the two pyramided Bt toxins expressed in the MON 89034 event, a commonly planted Bt maize trait in the Americas. Recent studies have documented that field resistance of the corn earworm, Helicoverpa zea (Boddie), to the Cry1A.105 toxin in maize plants has become widespread in the United States. To investigate the inheritance of resistance to Cry1A.105 in H. zea, two independent tests, each with various genetic crosses among susceptible and Cry1A.105-resistant populations, were performed. The responses of these susceptible, resistant, F1, F2, and backcrossed insect populations to Cry1A.105 were assayed using a diet overlay method. The bioassays showed that the resistance to Cry1A.105 in H. zea was inherited as a single, autosomal, nonrecessive gene. The nonrecessive nature of the resistance could be an important factor contributing to the widespread resistance of maize hybrids containing Cry1A.105 in the United States. The results indicate that resistance management strategies for Bt crops need to be refined to ensure that they are effective in delaying resistance evolution for nonrecessive resistance (nonhigh dose).

Impact of Transgenic Cry1Ab/2Aj Maize on Abundance of Non-Target Arthropods in the Field.

Transgenic Bacillus thuringiensis (Bt) maize has broad prospects for application in China. Before commercialization, it is necessary to assess possible ecological impacts, including impacts on non-target arthropods (NTAs) in the field. In the present study, transgenic Bt maize expressing cry1Ab/2Aj and its corresponding non-transformed near isoline were planted under the same environmental and agricultural conditions, and arthropods in the field were collected during the three main growth stages of maize. In a one year trial, the results showed the composition of NTA communities in the transgenic and control maize fields were similar. There were no significant differences for community-level parameters of species richness (S), Shannon–Wiener diversity index (H′), evenness index (J) and Simpson’s dominant concentration (C) between the two types of maize fields. Likewise, a Bray–Curtis dissimilarity and distance analysis showed that Cry1Ab/2Aj toxin exposure did not increase community dissimilarities between Bt and non-Bt maize plots and that the structure of the NTAs community was similar on the two maize varieties. Furthermore, planting of the transgenic cry1Ab/2Aj maize did not affect the density or composition of non-target decomposers, herbivores, predators, parasitoids and pollinator guilds. In summary, our results showed that planting of Bt maize producing Cry1Ab/Cry2Aj proteins do not adversely affect population dynamics and diversity of NTAs.

Varied frequencies of resistance alleles to Cry1Ab and Cry1Ac among Brazilian populations of the sugarcane borer, Diatraea saccharalis (F.).

Brazil is the largest grower of the world's 26 million ha of sugarcane, Saccharum officinarum. Pest damage mainly by the sugarcane borer, Diatraea saccharalis (F.), is a great challenge to the sugarcane industry. To control D.saccharalis, Brazil launched the world's first commercial use of Bt sugarcane in 2017. As part of the resistance management programs for Bt sugarcane planting, 535 F2 isoline families of D.saccharalis collected from three major sugarcane planting states (Goiás, Minas Gerais and São Paulo) in Brazil during 2019-2020 were screened for resistance to two Bt sugarcane varieties: CTC20BT expressing Cry1Ab and CTC9001BT expressing Cry1Ac. Here we report the results of the first study related to Bt resistance in a sugarcane cropping system. Larval survivorships of these families in an F2 screen on CTC20BT were highly correlated with their survival on CTC9001BT, whereas the Cry1Ac tissues exhibited greater insecticidal activities than Cry1Ab. Resistance allele frequencies (RAFs) for populations from Goiás and Minas Gerais were relatively low at 0.0034 for Cry1Ab and 0.0045 to Cry1Ac. By contrast, RAFs for São Paulo populations were considerably greater (0.0393 to Cry1Ab, 0.0245 to Cry1Ac). RAFs to Cry1Ab and Cry1Ac varied among Brazilian D.saccharalis populations. Prior selection resulting from an intensive use of single-gene Bt maize under low compliance of refuge planting could be a main factor contributing to the high RAF in São Paulo. The results suggest that mitigation measures including sufficient non-Bt maize refuge planting, effective resistance monitoring, and use of pyramided Bt sugarcane traits should be implemented promptly to prevent further increase in the RAF to ensure the sustainable use of Bt sugarcane in Brazil. To control Diatraea saccharalis, Brazil launched the world's first commercial use of Bt sugarcane in 2017. As part of the resistance management programs for Bt sugarcane planting in Brazil, 535 F2 isoline families of D.saccharalis collected from three major sugarcane planting states (Goiás, Minas Gerais and São Paulo) in Brazil during 2019-2020 were screened for resistance to Cry1Ab and Cry1Ac sugarcane plants Resistance allele frequencies (RAFs) for the populations from Goiás and Minas Gerais were relatively low at 0.0034 for Cry1Ab and 0.0045 to Cry1Ac. By contrast, RAFs for the São Paulo populations were considerably greater (0.0393 to Cry1Ab, 0.0245 to Cry1Ac). Prior selection resulting from an intensive use of single-gene Bt maize under low compliance of non-Bt maize refuge planting could be a main factor contributing to the high RAF in São Paulo. The results suggest that effective mitigation measures including sufficient non-Bt maize refuge planting, effective resistance monitoring and use of pyramided Bt sugarcane traits should be implemented promptly to prevent further increase in the RAF to ensure the sustainable use of Bt sugarcane in Brazil. © 2022 Society of Chemical Industry.

Transgenic Maize Has Insignificant Effects on the Diversity of Arthropods: A 3-Year Study.

In order to provide more evidence for the evaluation of the ecological risks of transgenic maize, arthropod population dynamics and biodiversity in fields planted with two kinds of transgenic maize (DBN9868, expressing the PAT and EPSPS genes, and DBN9936, expressing the Cry1Ab and EPSPS gene) were investigated by direct observation and trapping for three years. The recorded arthropod species belonged to 19 orders and 87 families, including Aphidoidea, Chrysomelidae, Coccinellidae, Chrysopidae and Araneae. The species richness, Shannon–Wiener diversity index, Pielou evenness index, dominance index and community similarity index of arthropod communities in maize fields were statistically analyzed, and the results showed that (1) the biodiversity difference of arthropod communities between transgenic maize and non-transgenic maize was smaller than that between different conventional cultivars; (2) the differences between ground-dwelling arthropod communities were less obvious than those between plant-inhabiting arthropod communities; and (3) Lepidoptera, the target pests of Bt maize, were not the dominant population in maize fields, and the dominant arthropod population in maize fields varied greatly between years and months. Combining those results, we concluded that the transgenic maize DBN9868 and DBN9936 had no significant effect on the arthropod communities in the field.

Climate change did not alter the effects of Bt maize on soil Collembola in northeast China

Bt maize is being increasingly cultivated worldwide as the effects of climate change are increasing globally. Bt maize IE09S034 and its near-isogenic non-Bt maize Zong 31 were used to investigate whether climate change alters the effects of Bt maize on soil Collembola. Warming and drought conditions were simulated using open-top chambers (OTC), and their effects on soil Collembola were evaluated. We found that the maize type had no significant effect on Collembola; however, the abundance and diversity of Collembola were significantly higher in the OTC than outside at the seedling stage; they were significantly lower in the OTC at the heading and mature stages. The interactions of the maize type with the OTC had no effect on these parameters. Therefore, Bt maize had no significant effect on soil Collembola, and the effects of climate warming and drought on soil Collembola depended on the ambient climatic conditions. When the temperature was low, collembolan abundance and diversity were promoted by warming; however, when the temperature was high and the humidity was low, collembolan abundance and diversity were inhibited by warming and drought. The climate changes simulated by the OTC did not alter the effects of Bt maize on soil Collembola.

Susceptibilities of the Invasive Fall Armyworm (Spodopterafrugiperda) to the Insecticidal Proteins of Bt maize in China

To control the fall armyworm (FAW), Spodoptera frugiperda (Smith), a serious threat to maize production in China, the Chinese government has issued biosafety certificates for transgenic insect-resistant maize expressing Bt (Bacillus thuringiensis) toxins including Bt-Cry1Ab maize (crop event DBN9936), Bt-Vip3Aa maize (event DBN9501), Bt-(Cry1Ab+Vip3Aa) maize with superimposed traits (event DBN9936 × DBN9501) and Bt-(Cry1Ab+Vip3Aa) maize with superimposed traits (event Bt11 × MIR162), but the susceptibility baselines of geographically distinct FAW populations to these events, which form the basis for managing resistance development in the pest to these events, are not clear. We used the diet-incorporated bioassays method to detect the susceptibilities of the seven FAW populations collected from Yunnan, Henan and Hubei provinces in China in 2021 to the insecticidal proteins of the four Bt maize events. The result showed that the susceptibilities of different geographical populations to Bt insecticidal proteins were significantly different. In the seven populations, the range in median lethal concentrations (LC50) of Cry1Ab expressed in DBN9936 was 0.87–2.63 μg/g, 0.14–0.30 μg/g for Vip3Aa expressed in DBN9501, 0.78–1.86 μg/g for Cry1Ab+Vip3Aa expressed in DBN9936 × DBN9501, and 0.36–1.42 μg/g for CryAb+Vip3Aa expressed in Bt11 × MIR162. The growth inhibition responses also showed that the susceptibilities varied with the different median growth inhibitory concentration (GIC50) ranges (0.38–1.22, 0.08–0.28, 0.28–0.87, and 0.24–0.78 μg/g, respectively). The variations in the ranges of the susceptibility baselines of the geographical populations of fall armyworm in China to the insecticidal proteins expressed in the four events provide a scientific basis for monitoring FAW population resistance to Bt maize and managing the populations using different Bt maize events.

Could the Presence of Thrips AFFECT the Yield Potential of Genetically Modified and Conventional Maize?

Maize pests like Ostrinia nubilalis and Diabrotica virgifera virgifera are eradicated using genetically modified maize. This study’s goal was to see if the genetically modified maize MON810 is also toxic to thrips communities on maize. The impact of Bt maize on thrips diversity and abundance, as well as yield losses, was studied in the field in Borovce for three years (Slovakia). The study used 10 Bt and 10 non-Bt maize cultivars. Thrips were monitored every two weeks during the season using transparent sticky traps installed on the experimental plots (one per plot, 20 per year). In total, 3426 thrips were caught. Thrips populations usually peak around the end of July at BBCH55. Among the species identified were Limothrips denticornis, Limothrips cerealium, Haplothrips aculeatus, Frankliniella schultzei, Frankliniella occidentalis, Thrips tabaci, Aeolothrips fasciatus, Frankliniella tenuicornis, and Chirothrips spp. We found that MON810 maize had no effect on the occurrence or composition of thrips. Their presence was affected by the maize growth phase and growing seasons and partially by the weather. The direct effect on the grain yield was not confirmed. Our research contributed to scientific knowledge of thrips communities found on maize plants in Central Europe, including Bt maize.

Toxicometabolomic profiling of resistant and susceptible western corn rootworm larvae feeding on Bt maize seedlings

The western corn rootworm (WCR), Diabrotica virgifera virgifera LeConte, is the most serious pest of maize (Zea mays L.) in the U.S. Corn Belt and parts of Europe. Transgenic maize hybrids expressing at least one of the four currently available insecticidal toxins from Bacillus thuringiensis (Bt) Berliner, currently the most widely adopted control method in continuous maize, have faltered due to the emergence of resistance. The resistance mechanisms of WCR to Bt toxins are not fully understood. We identified metabolic profiles of susceptible and resistant WCR larvae fed on maize hybrids expressing each of three available Cry3 proteins (eCry3Ab1, mCry3A, and Cry3Bb1) targeting corn rootworms and a control non-Bt maize via an untargeted metabolomics approach. Over 580 unique metabolites found in WCR larvae were classified into different pathways (amino acids, carbohydrates, cofactors and vitamins, energy, lipid, nucleotide, peptide, and xenobiotics). By exploring shifts in WCR larval metabolome exclusively by Bt toxins, several candidate metabolites and metabolic pathways were identified in susceptible and resistant larvae that may be involved in defense against or recovery from Bt ingestion by these larvae. These findings would provide mechanistic insights into altered metabolic pathways associated with the resistance mechanisms of WCR to Bt toxins.

Assessment of the 2020 post-market environmental monitoring report on the cultivation of genetically modified maize MON 810 in the EU.

Following a request from the European Commission; the European Food Safety Authority (EFSA) assessed the 2020 post‐market environmental monitoring (PMEM) report on the cultivation of Cry1Ab‐expressing maize event MON 810. Like previous years, there was full compliance with refuge requirement in Portugal and partial compliance with refuge requirements by Spanish farmers growing MON 810 varieties. European and Mediterranean corn borer populations collected from north‐eastern Spain during the 2020 maize growing season and tested for Cry1Ab susceptibility show no symptoms of resistance to maize MON 810. The assessment of farmer questionnaires and relevant scientific publications does not indicate any unanticipated adverse effects on human and animal health or the environment arising from the cultivation of maize MON 810. Overall, EFSA concludes that the evidence reported in the 2020 PMEM report does not invalidate previous EFSA evaluations on the safety of maize MON 810. However, as in previous years, EFSA identifies shortcomings on resistance monitoring that need revision in future reports. In particular, the monitoring plan, as implemented in 2020, is not sufficiently sensitive to detect the recommended 3% resistance allele frequency. Consequently, EFSA strongly recommends the consent holder to achieve full compliance with refuge obligations in areas where adoption of maize MON 810 is high and increase the sensitivity of the monitoring plan by performing periodic F2‐screens on corn borer populations from north‐eastern Spain. EFSA recommends revising the farmer questionnaires when new characteristics of the receiving environment emerge which are relevant for the environmental risk assessment of MON 810 such as the emergence of teosinte. EFSA encourages the Competent authorities of concerned EU Member States, the consent holder and environmental networks to engage in a dialogue to develop a framework on how to best identify and report unexpected adverse effects from the cultivation of Bt maize varieties.

Relative fitness of susceptible and Cry1A.105/Cry2Ab2-single-/dual-protein-resistant Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae) on non-Bt diet and a diet containing a low concentration of two proteins.

Helicoverpa zea (Boddie) is a destructive agricultural pest species that is targeted by both Bacillus thuringiensis (Bt) maize and cotton in the United States. Cry1A.105 and Cry2Ab2 are two Bt proteins expressed in a widely planted maize event MON 89034. In this study, two tests (Test-I and Test-II) were conducted to evaluate the relative fitness of Bt-susceptible and -resistant H. zea on non-Bt diet (Test-I and Test-II) and a diet containing a mix of Cry1A.105 and Cry2Ab2 at a low concentration (Test-II only). Insect populations evaluated in Test-I were two Bt-susceptible strains and three Bt-resistant strains (a single-protein Cry1A.105-, a single-protein Cry2Ab2-, and a dual-protein Cry1A.105/Cry2Ab2-resistant strains). Test-II analyzed the same two susceptible strains, three backcrossed-and-reselected Cry1A.105/Cry2Ab2-single-/dual-protein-resistant strains, and three F1 heterozygous strains. Measurements of life table parameters showed that neither the single- nor dual-protein Cry1A.105/Cry2Ab2 resistance in H. zea was associated with fitness costs under the test conditions. The single Cry protein resistances at a concentration of a mix of Cry1A.105 and Cry2Ab2 that resulted in a zero net reproductive rate for the two susceptible strains were functionally incomplete recessive or codominant, and the dual-protein resistance was completely dominant. The lack of fitness costs could be a factor contributing to the rapid revolution of resistance to the Cry proteins in this species. Data generated from this study should aid our understanding of Cry protein resistance evolution and help in refining IRM programs for H. zea.

EFFECT OF EARWORM INJURIES ON FUMONISINS PRODUCTION IN Bt AND NON-Bt MAIZE

Tests were carried out to assess fumonisins production due to lepidopteran feeding on the ears of the hybrid DKB 390VTPRO (Cry1A105/ Cry2Ab2) and in its non-Bt isogenic version. Maize ears were harvested and classified according to injury size, and fumonisin levels for each injury class were quantified. There were no significant differences between Bt maize and non-Bt maize in fumonisin production. However, the injury size due to earworm feeding was significant for fumonisin occurrence. The greater the injury, the higher the fumonisins level.

Biochemical analyses demonstrate that Bt maize has no adverse effects on Eisenia fetida.

The potential effects of Bt (Bacillus thuringiensis) maize on non-target organisms should be evaluated before such maize is commercially planted. Earthworms play an indispensable role in the soil ecosystem; act as important bio-indicators of soil quality and environmental pollution. Therefore, earthworms are often used as the object to evaluate the non-target effect of Bt maize. To accelerate the commercialization of transgenic maize in China, a 90-day Eisenia fetida feeding experiment was conducted to evaluate the potential effects of Bt maize line, BT799—which was developed by China Agricultural University and contains the Cry1Ac gene—and its non-Bt conventional isoline—Zheng 58—on E. fetida. Our results showed that the Bt maize line had no significant effects on the growth, reproduction, or enzymatic activities of these earthworms. In summary, Bt maize had no toxic effects on E. fetida.