Transgenic Bt Research Articles

Effect of Bt traits on transgenic rice’s growth and weed competitiveness

Transgene escape could lead to genetically modified rice establishing wild populations in the natural environment and competing for survival space with weeds. However, whether the expression of the Bacillus thuringiensis (Bt) gene in rice will alter the relationship between transgene plants and weeds and induce undesirable environmental consequences are poorly understood. Thus, field experiments were conducted to investigate the weed competitiveness and assess the ecological risk of transgenic Bt rice under herbicide-free and lepidopterous pest-controlled environments. Results showed that weed–rice competition in the direct-sowing (DS) field was earlier and more severe than that in the transplanting (TP) field, which resulted in a significant decrease in biomass and yield in DS. However, conventional Bt and non-Bt rice yield was not significantly different. The weed number, weed coverage ratio, and weed diversity of conventional Bt rice were significantly higher than those of non-Bt rice at the early growth and mature stages, especially in DS plots, suggesting that Bt traits did not increase the weed competitiveness of transgenic rice and had no negative effect on weed diversity. Grain yield and weed number varied between different hybrid rice lines, but those differences were insignificant between Bt and non-Bt rice. The number of insects increased with the increase of weeds in hybrid rice plots, whereas the insect number and diversity did not display a significant difference between Bt and non-Bt rice. Therefore, the ecological risk of transgenic Bt rice is comparable to non-Bt rice.

Population Dynamics of Sucking Insect Pest and Predator, Chrysoperla carnea in Transgenic Bt Cotton and Non Bt Cotton Varieties

Population Dynamics of Sucking Insect Pest and Predator, Chrysoperla carnea in Transgenic Bt Cotton and Non Bt Cotton Varieties

Development and reproduction of Tetranychus cinnabarinus (Acari: Tetranychiae) on transgenic insect-resistant cotton plants

The effects of two insect-resistant transgenic cotton strains (transgenic Bt pest-resistant cotton Zhongkangza 5 and Lumianyan 23, transgenic Bt+CpTI pest-resistant cotton sGK958 and Zhongmiansuo 45) on the growth and reproduction of Tetranychus cinnabarinus was examined in comparison with non-transgenic cotton (K836) at 70% relative humidity and 30±0.5 ℃. The results showed that T. cinnabarinus fed on transgenic Bt cotton and transgenic Bt+CpTI cotton differed significantly from those on conventional cotton in development time of various stages. Furthermore, the development times of mites on transgenic Bt cotton and transgenic Bt+CpTI cotton were the same, but the development times of T. cinnabarinus fed on transgenic Bt pest-resistant cotton Zhongkangza 5 and Lumianyan 23 were different, as well as the development times of T. cinnabarinus fed on transgenic Bt+CpTI pest-resistant cotton sGK958 and Zhongmiansuo 45. The pre-oviposition period, oviposition period and the female mite life span were longer (1.44 d, 12.71 d, and 14.11 d respectively) on non-transgenic cotton than on transgenic cotton. The maximum fecundity was 75.61 eggs per female on non-transgenic cotton and the minimum fecundity (54.68 eggs per female) was observed in mites fed on sGK958. The net reproductive rate (R0) was the highest (55.000) on non-transgenic cotton, but was the smallest (37.219) on Zhongkangza 5. The intrinsic rate of increase (rm) was the highest (0.454) on non-transgenic cotton, but was the smallest (0.246) on Zhongkangza 5. The finite rate of increase (λ) was the highest (1.575) on non-transgenic cotton, but was the smallest (1.278) on Zhongkangza 5. The population doubling time (DT) was the shortest (1.526 d) on non-transgenic cotton, but was the longest (2.823 d) on Zhongkangza 5. The results of this study indicated the negative effects of transgenic cotton on the development and reproduction of T. cinnabarinus was significant: the larvae had the lowest survival rate after feeding on five kinds of cotton, while deutonymphs had the highest survival rate; the hatching rate and deutonymph survival rate of T. cinnabarinus fed on CK were the highest, while the hatching rate and larval survival rate of the sGK958 were the lowest. Transgenic insect-resistant cotton basically showed significant effects on the development period of each stage and the whole generation of T. cinnabarinus, but there were no significant differences between univalent transgenic Bt cotton and bivalent transgenic Bt+CpTI cotton.

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

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

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.

Effects of Insect-Resistant Maize 2A-7 Expressing mCry1Ab and mCry2Ab on the Soil Ecosystem.

Transgenic maize 2A-7 expressing mCry1Ab and mCry2Ab has excellent resistance to lepidopteran pests. Previous studies have investigated the effects of several Bacillus thuringiensis (Bt) proteins on the soil. However, the effects of artificially modified Bt proteins on soil ecosystems are still unclear. To evaluate the effects of transgenic maize 2A-7 on soil, the physicochemical properties, enzyme activities and functional diversities of the microbial communities in rhizosphere soils from 2A-7 and its near-isogenic non-transgenic control Dongdan 6531 were analyzed at different developmental stages under field conditions. The alteration of six physicochemical properties (pH, total nitrogen, total phosphorus, organic matter, available phosphorus and alkali-hydrolyzed nitrogen) and six functional enzymes (catalase, alkaline phosphatase, sucrase, acid phosphatase, urease and alkaline protease) activities in the rhizosphere soils between the two maize cultivars were drastically correlated with plant growth stage, but not affected by the artificially modified Bt transgenes. An analysis of time-course Biolog data revealed that the functional diversity of microbial communities in the rhizosphere soil of 2A-7 and its control were similar at each developmental stage. The results suggest that transgenic maize 2A-7 has no significant impact on the soil ecosystem and provide valuable information on scientific safety assessments of 2A-7 and its commercial applications.

Environmental Behaviors of Bacillus thuringiensis (Bt) Insecticidal Proteins and Their Effects on Microbial Ecology.

Bt proteins are crystal proteins produced by Bacillus thuringiensis (Bt) in the early stage of spore formation that exhibit highly specific insecticidal activities. The application of Bt proteins primarily includes Bt transgenic plants and Bt biopesticides. Transgenic crops with insect resistance (via Bt)/herbicide tolerance comprise the largest global area of agricultural planting. After artificial modification, Bt insecticidal proteins expressed from Bt can be released into soils through root exudates, pollen, and plant residues. In addition, the construction of Bt recombinant engineered strains through genetic engineering has become a major focus of Bt biopesticides, and the expressed Bt proteins will also remain in soil environments. Bt proteins expressed and released by Bt transgenic plants and Bt recombinant strains are structurally and functionally quite different from Bt prototoxins naturally expressed by B. thuringiensis in soils. The former can thus be regarded as an environmentally exogenous substance with insecticidal toxicity that may have potential ecological risks. Consequently, biosafety evaluations must be conducted before field tests and production of Bt plants or recombinant strains. This review summarizes the adsorption, retention, and degradation behavior of Bt insecticidal proteins in soils, in addition to their impacts on soil physical and chemical properties along with soil microbial diversity. The review provides a scientific framework for evaluating the environmental biosafety of Bt transgenic plants, Bt transgenic microorganisms, and their expression products. In addition, prospective research targets, research methods, and evaluation methods are highlighted based on current research of Bt proteins.

Performance and field efficacy of indigenous egg parasitoid Trichogrammatoidea bactrae (Hymenoptera: Trichogrammatidae) against the cotton pink bollworm Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae) in transgenic Bt cotton

The pink bollworm (PBW) Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae) has emerged as a major pest of transgenic Bt cotton in India. The recent outbreak of PBW caused serious damage, and the existing management strategies become inefficient to reduce the pest incidence and crop yield losses. The development of environment-friendly and sustainable management strategies against PBW is urgently needed. Thus, laboratory tests were performed to evaluate 16 indigenous trichogrammatid species/strains to manage the PBW in transgenic Bt cotton. We compared the parasitism of trichogrammatid species/strains on PBW eggs and found that Trichogrammatoidea nr. robusta (79.6%), Trichogrammatoidea bactrae Nagaraja (76.4%) and Trichogramma chilonis Ishii (73.8%) parasitized a greater percentage of PBW eggs under laboratory conditions. Furthermore, the parasitism of Tr. nr. robusta, Tr. bactrae and T. chilonis were tested in cages. Results of cage study showed that Tr. bactrae parasitized at a higher rate the PBW eggs (73.2%) followed by T. chilonis (60.5%) and Tr. nr. robusta (48.6%). Subsequently, the effectiveness of Tr. bactrae was assessed for consecutive three years (2017–2020) in transgenic Bt cotton fields. We found that the 12 sequential releases of Tr. bactrae from the flowering stage onwards showed a significant reduction in the PBW incidence. Field released with Tr. bactrae or treated with insecticides reduced the number of larvae boll−1 by 1.5 and 3, respectively, the percentage of rosette flower by 1.7 and 2.7, respectively, and the percentage of locule damage by 2 and 2.5, respectively, compared to untreated control field. A higher yield of seed cotton was obtained both in Tr. bactrae released field (27.73 q h−1) and insecticide treated cotton field (31.68 q h−1) as compared to untreated control field. Our results showed that Tr. bactrae is a potential biocontrol agent of PBW. This could be used in biological control programme and may be incorporated in integrated pest management (IPM) programme against PBW in transgenic Bt cotton.

Transgenic Bt cotton expressing Cry1Ac/1Ab does not have detrimental effects on the predator Arma chinensis through its prey Helicoverpa armigera

Transgenic Bt cotton expressing Cry1Ac/1Ab does not have detrimental effects on the predator Arma chinensis through its prey Helicoverpa armigera

Evaluation of Chilo suppressalis resistance and analysis of CRY1C expression in transgenic rice

AbstractThe insect resistance of Bacillus thuringiensis (Bt) transgenic rice (Oryza sativa L.) is mainly determined by the transcription of the CRY1C gene and the translation process of the Cry1C protein. With this in mind, we analyzed CRY1C expression and Cry1C protein content in a transgenic Bt insect‐resistant restorer line and its F1 hybrids, evaluated the resistance to Chilo suppressalis of various lines of rice, and determined the 50% lethal concentration (LC50) of Cry1C for C. suppressalis. In four transgenic rice lines, the relative expression of CRY1C was highest at the heading stage in most tissues. Among different tissues from the same developmental stage, CRY1C expression was highest in leaves, followed by stems and panicles. The relative expression of CRY1C was higher in the parent restorer line than in the F1 hybrids. The LC50 of the Cry1C protein for C. suppressalis was 4.016 μg g−1, and the Cry1C protein expression level of transgenic insect‐resistant rice exceeded this threshold at the heading stages and in stems. We next analyzed the lethality of each strain toward C. suppressalis. After 48 h, the mortality rate of second‐instar C. suppressalis larvae feeding on transgenic stem tissue was higher at the heading stage than at the tiller stage and varied from 66.7 to 91.7%. By documenting the temporal and spatial expression of CRY1C and evaluating C. suppressalis resistance to Bt transgenic rice, the risk of pests and diseases during the rice production process can be greatly reduced.

The Effect of Resistance to Bt Corn on the Reproductive Output of Spodoptera frugiperda (Lepidoptera: Noctuidae).

Simple SummaryThe use of transgenic crops expressing insecticidal proteins from Bacillus thuringiensis (Bt) has been a successful strategy to control the fall armyworm (FAW) Spodoptera frugiperda. However, resistance to many Bt proteins has been observed, which could reduce the effectiveness of this approach as a control strategy. In this study, we compared the reproductive traits of susceptible and resistant FAW males and females to determine if there are costs associated with resistance. Our data provided clear evidence that the development of resistance to the Bt protein affected the reproductive capacity of resistant FAW males.The fall armyworm (FAW) Spodoptera frugiperda is the most significant lepidopteran corn pest in South American countries. Transgenic Bt corn, producing the Cry1Fa toxins, has been used to control this pest, but there is clear evidence that some FAW populations have developed resistance. To determine if there are costs associated with resistance, we compared the mass of adults, the duration of mating, and the mass of the first spermatophore produced, as well as the lifetime fecundity and fertility of once-mated susceptible (SS) and resistant (RR) females. Adult mass was affected by both sex and strain, with SS females being significantly larger than RR ones, while the inverse was true for males. RR pairs took significantly longer to mate than SS pairs, yet the mass of spermatophores produced by RR males was significantly less than those of SS males. The total number of eggs laid did not differ but the fertility of eggs from once-mated RR pairs was significantly lower than that of SS pairs. Our data provided clear evidence that the development of Bt resistance affected the reproductive capacity of resistant FAW.

An Overview on Insect Tolerance Transgenic Crops

Although transgenic crops have enhanced insect pest control, their effectiveness has diminished due to pest resistance. Humans examined global monitoring data from the very first two decades of genetically engineered crops, with each occurrence representing one pest species' response to one Bacillus thuringiensis insecticidal protein in one country (Bt). Pest tolerance to transgenic crops' Bt crystalline (Cry) proteins has increased from three cases in 2005 to sixteen cases in 2016. Hereditary change that is bug-free innovation is fastgrowing, with enormous exploration effort in both the commercial and legislative regions. Although the bacterium Bacillus thuringiensis is the most widely advertised bug-safe transgenic plant, a wide range of traits from higher plants, particularly those producing stomachrelated chemical inhibitors or lectins, have also been introduced into crop cultivars. So far, the quality of opposition from various microbes and species has only been used in a few circumstances.

Accumulation of Cry proteins in soil released from Bt rice after planting for multiple years

Cry protein residue and accumulation in soil are two important components of the environmental safety assessment for the plantation of transgenic Bt crops. Several Bt rice lines with good commercial prospects have been developed in China, but it is unclear whether Cry proteins will accumulate in soils after multiple years of Bt rice cultivation. We planted the transgenic Bt rice lines cry1Ab/1Ac Minghui 63 (Huahui No. 1) and cry2A Minghui 63 for 9 years in the same field. The Cry proteins in the rhizosphere soil were estimated with enzyme linked immunosorbent assay (ELISA) at tillering stage and on the 60th day after harvest in each year. The Cry protein residues during the seedling, flowering and ripening stages were estimated in the first year (2012) and the last year (2020) of the experiment. In 2012, the concentration of Cry1Ab/1Ac in the rhizosphere soil of Huahui No. 1 was 1.25, 1.77, 1.97, 1.71 and 0.30 ng·g-1 at the seedling, tillering, flowering, ripening stages and on the 60th day after harvest, respectively. In 2020, the corresponding values were 1.30, 1.69, 2.03, 1.77, and 0.43 ng·g-1. In 2012, the concentration of Cry2A in rhizosphere soil of line cry2A Minghui 63 was 0.91, 1.52, 1.53, 1.37, and 0.12 ng·g-1 at the seedling, tillering, flowering, ripening stages and on the 60th day after harvest, respectively. The corresponding values in 2020 were 0.95, 1.43, 1.61, 1.40, and 0.15 ng·g-1. Results of multi-way ANOVA showed that the effect of year was not significant, but the effects of rice variety and growth stage were significant. Our results indicated that Cry proteins could be detected in rhizosphere soil during the growth stages of Bt rice, but would be degraded by 60 d after harvest, and that the concentrations of Cry proteins in the soil would not accumulate across multiple planting years.

A 6-year field monitoring of fall armyworm, Spodoptera frugiperda, in transgenic Bt maize in Brazil

A 6-year field monitoring study was designed to compare the presence of fall armyworm Spodoptera frugiperda (J. E. Smith), leaf injury, its parasitoids, 100 seed weight, and seed yield of Bt maize hybrids approved for commercialization in the Brazilian market. Field trials were planted in two municipalities, divided into two periods, from 2011 to 2014 (period I), and due to the approval of different Bt hybrids, from 2015 to 2016 (period II). Treatments were Bt, non-Bt maize and all non-Bt maize sprayed with insecticide methomyl. Six Bt-maize hybrids were planted, expressing the following proteins: Cry1Ab, Cry1F, Cry1A.105 (Cry1Ab +Cry1Ac +Cry1F), Cry2Ab2a and Vip3. In 2015 and 2016 Bt Powercore was planted due to its commercial approval. The number of S. frugiperda larvae for most Bt hybrids was lower than on non-Bt hybrids, except for Fórmula TL and Herculex in period II, in both municipalities. In period I, Bt hybrids VT, VT 2 and Viptera showed almost no injury on their leaves, despite the high number of fall armyworm larvae found in plants. Different parasitoids emerged from larvae from Bt and non Bt hybrids: Archytas sp., Campoletis sp., Chelonus sp., Eiphosoma sp. and Ophion luteus. The average 100 seed weight was higher in municipality from Sete Lagoas for all Bt hybrids, non-Bt hybrids and non-Bt hybrids sprayed with methomyl, when compared to Nova Porteirinha during period I. Fórmula TL, non-Bt Fórmula TL sprayed with methomyl, and non-Bt Fórmula TL showed the lowest seed yield in both municipalities and periods.

Inheritance and molecular tagging of genes introgressed from Gossypium arboreum to G. hirsutum for leafhopper tolerance

Cotton cultivation is conquered by transgenic Bt upland cotton hybrids in India. Bt gene does not provide resistance against sucking insect pests. Due to the inherent vulnerability of extant Bt cotton hybrids to sap-sucking insect pests including leafhopper, upland cotton cultivation is seriously threatened by surging populations of these pests. Consistent and extensive screening of upland cotton germplasm over the years has revealed absence of adequate resistance against leafhopper. Here, we report introgression of leafhopper tolerance from a diploid A-genome cotton species, Gossypium arboreum into G. hirsutum. The dominance of leafhopper tolerance was observed over its susceptibility. Genetic analysis revealed that tolerance to leafhopper was inherited in a simple Mendelian fashion and was controlled by two genes, either singly or in combination. Using bulked segregant analysis, two simple-sequence repeat markers, namely NAU 922 and BNL 1705, located on chromosomes A5 and A11 respectively, were tagged with leafhopper tolerance. To the best of our knowledge, this is the first report of molecular tagging of leafhopper tolerance introgressed from G. arboreum into G. hirsutum. A significant negative association was observed between leaf trichome density and leafhopper nymph population.

Moderate stability of a scissor double fluorescent triple helix molecular switch for the ultrasensitive biosensing of crop transgene

Schematic of the ultrasensitive biosensing of special genes. (I: traditional molecular beacon detection method; II: scissor DFTHMS; III: three cases of BHQ-1-TFO).

Effects of Nitrogenous Fertilization and some Insecticides on the Natural Enemies of Transgenic Bt Cotton Pests

Field assessment of integrated management of BT cotton pests was carried out in two consecutive seasons; 2016/2017 and 2017/2018 in the experimental research farm of the Kassala University, Sudan. Four insecticides (imidacloprid, abamectin, profenofos, and lufenuron) from different chemical groups and with a different mode of action and three levels (43.81 kgha-1, 87.62 kgha-1, and 131.43 kgha-1) of soil-applied nitrogen were tested in the IPM package. Insecticides were applied at the recommended doses. A total of 7 weekly counts of prevailing natural enemies [Chrysoperla carnea (Stephens) and Aenasius bambawalei Hayat] were carried out for 4 weeks before spraying and 3 weeks post spraying starting the 3rd week from spraying. Results indicated that nitrogen level exerted no significant effects on the populations of prevailing natural enemies; C. carnea and A. bambawalei. Based on average post spray counts and percentage reduction over the control, all insecticide treatments significantly reduced the population of the natural enemies. Imidacloprid and profenofos exerted the highest reduction of C. carnea population followed by abamectin and lufenuron (56.03, 48.25, 07.78 and 06.61% respectively) in the first season, while profenofos, imidacloprid, lufenuron, and abamectin induced the highest reductions (55.94, 45.05, 17.57 and 17.33% respectively) in the second season. On the other hand, reductions in A. bambawalei population (abundant in season 1 only) followed the order; imidacloprid, lufenuron, abmectin, and profenofos (03.95, 02.63, 202.63, and 01.32%, respectively). Interactions between nitrogen fertilization and insecticide were not significant as measured by the population of prevailing natural enemies.

Primeiro registro de Rachiplusia nu (Guenée, 1852) (Lepidoptera: Noctuidae) sobrevivendo em soja Bt no Brasil

Loopers are important defoliators in several crop species. Among the loopers attacking non-Bt soybean cultivars, Chrysodeixis includens (Walker, [1858]) was the most common. The use of trangenic Bt soybean in appromately 70% of the soybean fields in Brazil led to a decrease in the loopers in these fields. However, technical field specialists and soybean producers recently observed Plusiinae larvae damaging transgenic Bt soybean, posing a risk over the Bt technology. Therefore, the aim of this study was to identify and confirm the catterpillar species feeding on transgenic Bt soybean fields in Brazil. Larvae and soybean leaf samples were collected in 12 soybean-producing locations from four Brazillian States. Soybean leaf samples were tested to confirm whether they were transgenic Bt. Larvae were reared in artificial diet and submitted to feeding trials on non-transgenic and transgenic Bt soybean leaves. The species identification was perfomed by amplicon sequencing of the cytochrome oxidase I (COI) gene of eight larvae per local. All 12 populations fed in the transgenic Bt soybean and the sequencing analysis of COI determined that they belong to Rachiplusia nu (Guenée, 1852) with 100% similarity to the COI sequences available in NCBI for this species. These results suggest that the R. nu species is not controlled by the genetic modification event present in the tested soybean variety and highlights the need for additional looper management control strategies, such as insecticide application, for controlling this insect pest in transgenic Bt soybean.

Up-regulation of apoptotic- and cell survival-related gene pathways following exposures of western corn rootworm to B. thuringiensis crystalline pesticidal proteins in transgenic maize roots

BackgroundResistance of pest insect species to insecticides, including B. thuringiensis (Bt) pesticidal proteins expressed by transgenic plants, is a threat to global food security. Despite the western corn rootworm, Diabrotica virgifera virgifera, being a major pest of maize and having populations showing increasing levels of resistance to hybrids expressing Bt pesticidal proteins, the cell mechanisms leading to mortality are not fully understood.ResultsTwenty unique RNA-seq libraries from the Bt susceptible D. v. virgifera inbred line Ped12, representing all growth stages and a range of different adult and larval exposures, were assembled into a reference transcriptome. Ten-day exposures of Ped12 larvae to transgenic Bt Cry3Bb1 and Gpp34/Tpp35Ab1 maize roots showed significant differential expression of 1055 and 1374 transcripts, respectively, compared to cohorts on non-Bt maize. Among these, 696 were differentially expressed in both Cry3Bb1 and Gpp34/Tpp35Ab1 maize exposures. Differentially-expressed transcripts encoded protein domains putatively involved in detoxification, metabolism, binding, and transport, were, in part, shared among transcripts that changed significantly following exposures to the entomopathogens Heterorhabditis bacteriophora and Metarhizium anisopliae. Differentially expressed transcripts in common between Bt and entomopathogen treatments encode proteins in general stress response pathways, including putative Bt binding receptors from the ATP binding cassette transporter superfamily. Putative caspases, pro- and anti-apoptotic factors, as well as endoplasmic reticulum (ER) stress-response factors were identified among transcripts uniquely up-regulated following exposure to either Bt protein.ConclusionsOur study suggests that the up-regulation of genes involved in ER stress management and apoptotic progression may be important in determining cell fate following exposure of susceptible D. v. virgifera larvae to Bt maize roots. This study provides novel insights into insect response to Bt intoxication, and a possible framework for future investigations of resistance mechanisms.

Trait-based comparison of transgenic Bt rice and its non-Bt counterpart in response to soil copper pollution.

Transgenic Bacillus thuringiensis (Bt) rice can provide economic and environmental benefits under the current increasing demand for food and socioeconomic pressures for sustainability. However, information about the ecological adaptation of Bt rice under nontarget environmental stress is still lacking. This study compared the adaptability of one Bt rice and its nontransgenic counterpart to soil copper (Cu) pollution in terms of agronomic and physiological traits. With Cu addition, grain yield and biomass of both cultivars were significantly decreased. Within the same Cu treatment, Bt rice exhibited higher biomass and close plant height, chlorophyll content, grain yield, and grain quality compared with non-Bt rice, except for the grain yield with a 35 mg kg-1 Cu addition with respect to which Bt rice was significantly lower by 22%. The Cu content in Bt rice was generally lower, whereas the antioxidant enzyme activity and lipid peroxidation were stronger than the non-Bt. These results demonstrated that Bt rice exhibited close adaptability but higher Cu tolerance compared with the non-Bt under Cu stress.