non-Bt Rice 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.

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.

Differential impact of Bt-transgenic rice plantings on bacterial community in three niches over consecutive years

Transgenic-Bacillus thuringiensis (Bt) crops express insecticidal proteins, which can accumulate in plants and soil where they may influence microbial populations. The impact of Bt crops on bacterial communities has only been assessed under short-term, and results have been contradictory. Here, we analyzed the bacterial communities in three niches, rhizosphere soil (RS), root endosphere (RE) and leaf endosphere (LE), of three Bt rice and their non-Bt parental lines for three consecutive years by high-throughput sequencing. In principal coordinate analysis (PCoA) and PERMANOVA (Adonis) analysis, operational taxonomic units (OTUs) were clustered primarily by niche type and differed significantly in the RE and LE but not in the RS between each of three Bt lines compared with the non-Bt rice line, and not in each respective niche among the three Bt rice lines. The bacterial communities in the RS of different rice lines over the 3 years were clustered mainly by year rather than by lines. The differential bacterial taxa among the lines did not overlap between years, presumably because Cry proteins are rapidly degraded in the soil. A network analysis of RS bacterial communities showed that the network complexity and density for the three Bt rice lines did not decrease compared with those for the non-Bt line. In conclusion, our results demonstrated that bacterial communities differed significantly in RE and LE between Bt and non-Bt rice lines, but the differences were mild and transient, and had no adverse impact on RS over the 3 years. This study provides favorable evidence in support of the commercialization of Bt rice.

Metabolic Analysis Reveals Cry1C Gene Transformation Does Not Affect the Sensitivity of Rice to Rice Dwarf Virus.

Metabolomics is beginning to be used for assessing unintended changes in genetically modified (GM) crops. To investigate whether Cry1C gene transformation would induce metabolic changes in rice plants, and whether the metabolic changes would pose potential risks when Cry1C rice plants are exposed to rice dwarf virus (RDV), the metabolic profiles of Cry1C rice T1C-19 and its non-Bt parental rice MH63 under RDV-free and RDV-infected status were analyzed using gas chromatography–mass spectrometry (GC-MS). Compared to MH63 rice, slice difference was detected in T1C-19 under RDV-free conditions (less than 3%), while much more metabolites showed significant response to RDV infection in T1C-19 (15.6%) and in MH63 (5.0%). Pathway analysis showed biosynthesis of lysine, valine, leucine, and isoleucine may be affected by RDV infection in T1C-19. No significant difference in the contents of free amino acids (AAs) was found between T1C-19 and MH63 rice, and the free AA contents of the two rice plants showed similar responses to RDV infection. Furthermore, no significant differences of the RDV infection rates between T1C-19 and MH63 were detected. Our results showed the Cry1C gene transformation did not affect the sensitivity of rice to RDV, indicating Cry1C rice would not aggravate the epidemic and dispersal of RDV.

Compositional equivalence assessment of insect-resistant genetically modified rice using multiple statistical analyses

ABSTRACT The safety of transgenic Bt rice containing bacteria-derived mCry1Ac gene from Bacillus thuringiensis (Bt) was assessed by conducting field trials at two locations for two consecutive years in South Korea, using the near-isogenic line comparator rice cultivar (‘Ilmi’, non-Bt rice) and four commercial cultivars as references. Compositional analyses included measurement of proximates, minerals, amino acids, fatty acids, vitamins, and antinutrients. Significant differences between Bt rice and non-Bt rice were detected; however, all differences were within the reference range. The statistical analyses, including analysis of % variability, analysis of similarities (ANOISM), similarity percentage (SIMPER) analysis, and permutational multivariate analysis of variance (PERMANOVA) were performed to study factors contributing to compositional variability. The multivariate analyses revealed that environmental factors more influenced rice components’ variability than by genetic factors. This approach was shown to be a powerful method to provide meaningful evaluations between Bt rice and its comparators. In this study, Bt rice was proved to be compositionally equivalent to conventional rice varieties through multiple statistical methods.

Cry1C rice doesn\u2019t affect the ecological fitness of rice brown planthopper, Nilaparvata lugens either under RDV stress or not

The potential risks of Bt rice on non-target arthropods (NTAs) should be evaluated and defined before commercial production. Recently, effects of Bt rice on NTAs under abiotic and biotic stress conditions attracted much attention. Here we reported the effects of Bt rice T1C-19 (Cry1C rice) on the non-target herbivore, Nilaparvata lugens (rice brown planthopper, BPH) with or without RDV (rice dwarf virus) infection conditions. BPH showed no feeding and oviposition preference between Bt rice T1C-19 and its non-Bt parental rice Minghui 63 (MH63), as well as between RDV-infected and RDV-free rice plants. Meanwhile, rice type, RDV infection status, and their interaction had little impacts on the survival, development and fecundity of BPH. By comparison with non-Bt control, Bt rice T1C-19 with or without RDV infection had no significant effects on the life-table parameters of BPH including rm, R0, T, DT and λ. Thus, it could be concluded that Bt rice T1C-19 doesn’t affect the ecological fitness of BPH either under RDV stress or not.

Evaluating the effects of transgenic Bt rice cultivation on soil stability.

Insecticidal crystal (Cry) proteins produced by genetically modified rice that enter the soil via pollen dispersal, plant residues, and root exudation may disturb soil health. In the present study, we assessed the influences of transgenic Bt rice (i.e., HH1 with Cry1Ab/Cry1Ac) cultivation on the dynamics of soil carbon and nutrients under field conditions during 2013-2016. Transgenic treatments (transgenic Bt rice vs. its parental line (i.e., MH63) of non-Bt rice) have no consistently significant effects on soil property, including available nitrogen, available phosphorus, available potassium, total nitrogen, and total phosphorus, while apparent seasonal changes were observed. Besides, the variations of soil nutrients in the paddy field of transgenic Bt rice did not exceed their resistance capacities, except total organic carbon (TOC; RS (resistance) = 1.51) and total potassium (TK; RS = 2.62) in 2013 and TK (RS = 1.94) in 2014. However, the TOC and soil nutrient of TK in the paddy field of transgenic Bt rice have recovered to the pre-perturbation status after harvest (RL (resilience) = 1.01, F = 0.01, P = 0.91; RL = 0.98, F = 0.34, P = 0.58; RL = 0.99, F = 1.26, P = 0.29). Moreover, the paddy yield of transgenic Bt rice was consistently higher than that of its parental line of non-Bt rice. These results suggested that the cultivation of transgenic Bt rice has no adverse impact on soil stability in terms of soil carbon and nutrients and paddy yield.

Effects of Pest Management Practices on Soil Nematode Abundance, Diversity, Metabolic Footprint and Community Composition Under Paddy Rice Fields.

The wide-scale adoption of transgenic crops has aroused public concern towards potential impacts to the ecological services of soil fauna, such as soil nematodes. However, few studies has examined whether the cultivation of transgenic rice would pose greater threats to soil nematode community and associated ecological functions than insecticides application. Moreover, what are determinants of soil nematode community in paddy fields remains unclear. During a 3-year field study, rhizosphere soil samples of transgenic-Bt rice, its counterpart non-Bt parental rice and not-Bt rice with insecticides application were taken at four times in the rice developmental cycle using a random block design with three replications for each treatment. We hypothesized that the effects of pest management practice on soil nematode abundance and metabolic footprint change with trophic group and sampling time. We also predicted there were significant differences in structure and composition of soil nematode community across the three treatments examined and sampling times. In agreement with our expectation, the effects of pest management practice on nematode abundance and metabolic footprints depend on trophic group and sampling time. However, pest management practice exerted no apparent effect on nematode diversity and community composition. Soil nutrient availability and C:N molar ratio are the primary regulating factor of soil nematode community in rice paddy fields. In conclusion, our findings implied that changes in abundance, diversity, metabolic footprints associated with the crop growth stage overweighed the application of Bt rice and insecticides. The cultivation of Bt rice Huahui-1 exerted no measurable adverse effect on soil nematode community in rhizosphere soil over 3 years of rice cropping.

Effects of transgenic Bt rice lines with single Cry1Ab and fused Cry1Ab/Cry1Ac on the abundance dynamics and community diversity of soil mites

ABSTRACTRisk assessment and ecological effects are a concern of transgenic rice. In this study, the effects of three lines of Bt rice expressing single Cry1Ab protein (Kemingdao: cv. KMD) and fused Cry1Ab/Cry1Ac proteins (Huahui 1: cv. HH1; Bt Shanyou 63: cv. Bt-SY63) on soil mite community were investigated under field conditions. Transgenic treatment (cv. Bt-rice vs. non-Bt rice) significantly decreased the community index of Margalef’s richness (SR) of soil mite in KMD, and significantly increased the abundance and the community indexes of Shannon diversity (H’), Pielou’s evenness (J) and SR of soil mite in Bt-SY63 (p < 0.05). Transgene type (cv. KMD vs. HH1) did not significantly affect the composition, abundance and the community index (p > 0.05). Breeding type (cv. HH1 vs. Bt-SY63) significantly changed the composition and markedly improved the abundance and the J value in Bt-SY63 (p < 0.05). However, seasonal and inter-annual changes were apparent, and the Bt effects were not consistent at all for the different plant backgrounds over a 2-year period. These results suggested that the cultivation of Bt rice has a significant but transient effect on soil mite community.

Environmental impacts of transgenic Bt rice and non-Bt rice cultivars in northern Iran

Abstract In the future, rice production is likely to be impacted by climate change and associated risks including pest complexes and consumption of chemical inputs, thereby decreasing production at a regional scale and one of the major global concerns. In fact, among the biotic stresses, damage caused by insect pests, which can be categorized as either minor or major pests, can severely constrain the potential yield of rice. Hence, planting transgenic rice is considered a solution for reducing environmental and human health impacts. Therefore, in this research, life cycle assessment for environmental and human health impacts of transgenic and non-transgenic rice cultivars was considered. Hence, four transgenic lines (driven from back cross of Khazar cultivar with transgenic line of Tarom Molaii) along with conventional cultivars (non-transgenic parents) were cultivated under the standard of biosafety protocol in three isolated sites in north of Iran in 2016. In order to conducted life cycle assessment, first, the results of each site were analyzed separately, and since there were not differences among the impact categories and indices in different sites, the average for the results of the three sites are being presented. Results show that decreased insecticides application in transgenic cultivars lowers the need for labor, machineries, and fuel, thereby contributing to reduction in use of energy and greenhouse gases emission from construction, transportation and application of inputs during cultivation. Furthermore, most investigated impact categories were obtained high for Tarom Molaii and Khazar and less for three transgenic lines. In addition, the most important categories were non-renewable energy, global warming, aquatic eutrophication, aquatic acidification, terrestrial acid/nutri, land occupation, terrestrial ecotoxicity, ozone layer depletion, ionizing radiation, respiratory inorganics, respiratory organics, cumulative energy demand, ecological footprint, greenhouse gas protocol, water footprint, carcinogens and non-carcinogens. Therefore, according to the findings of this research, it was observed that the emission amount of environmental pollutants has a positive correlation with the consumption of inputs and field management practices.

Interactive Effects of [CO2] and Temperature on Plant Chemistry of Transgenic Bt Rice and Population Dynamics of a Non-Target Planthopper, Nilaparvata lugens (Stål) under Different Levels of Soil Nitrogen.

Gaining a better understanding of the interactive effect of projected atmospheric CO2 level increase and the Earth’s rising temperature on plant chemistry (nutritional and defensive characteristics) of transgenic crops is essential when attempting to forecast the responses of target and non-target insects to climate change. In this study, effects of carbon dioxide (CO2; elevated versus ambient), temperature (T; high versus low), and their interactions on leaf nitrogen content (N%) and C:N ratio of transgenic Bt rice and its non-Bt isoline grown under low- and high-N fertilizer were systematically analyzed together with the resulting insect population dynamics of a non-target planthopper Nilaparvata lugens (Stâl) in open-top-chamber experiments. The results indicated that under low-N treatment, elevated CO2 at low T (i.e., eCO2) (compared to ambient CO2 at low T, i.e., CK) significantly decreased N% and Bt-toxin content and significantly increased C:N ratio in leaf sheath and leaf of Bt rice, especially during the tillering stage, whereas inverse effects of high T were shown on the plant chemistry of Bt rice, especially during heading stage. The combination of elevated CO2 and high T (i.e., Combined) (in contrast to CK) significantly increased N% and decreased C:N ratio in leaf sheath of Bt rice during the heading stage under low-N fertilizer, while significantly decreased N% and increased C:N ratio in leaf of Bt rice during the tillering stage, regardless of fertilizer-N level, and significantly increased Bt-toxin content in leaf sheath and leaf during the tillering stage under both low- and high-N. Moreover, no discernable relationships between Bt-toxin content and N% or leaf C:N ratio were observed at any CO2 or N levels evaluated. Furthermore, transgenic treatment, temperature and fertilizer-N level interactions, and CO2 and fertilizer-N level interactions all significantly affected the population dynamics of N. lugens. Specifically, high-N significantly enhanced the population dynamics of N. lugens fed on non-Bt rice grown under eTemp and Bt cultivar significantly reduced the population dynamics of N. lugens under eCO2 regardless of N fertilizer levels. The study demonstrates that the planting of transgenic Bt rice would not increase the risk of increased N. lugens severity under the combined condition of elevated CO2 and increased temperature, particularly under moderate level of N fertility.

Carbon and nitrogen partitioning of transgenic rice T2A-1 (Cry2A*) with different nitrogen treatments

Nitrogen (N) and carbon(C) metabolisms in plants were investigated to assess different responses of Bt and non-Bt rice to different N treatments. T2A-1 (Bt rice variety) inserted with Cry2A* protein to resist Lepidoptera and its parental line MH63 was adopted in this study. The total N accumulation presented no statistical difference. But nitrogen contents in different parts of rice plant were significantly different between the two lines, especially on leaf and spike part. This study revealed that the nitrogen in leaf of T2A-1 was far more than that of MH63; however, the nitrogen in spike of T2A-1 was less than that of MH63. In addition, MH63 assimilated more carbon than T2A-1. However, the distribution proportion of carbon in leaf, stem and spike of T2A-1 and MH63 were both 1:1:1. What’s more, our study of the difference in metabolism pathway based on proteomics analysis provided more insights on the responses of two lines of Bt and non-Bt rice to different N treatments. And amino acid metabolism, energy metabolism, and carbohydrate metabolism presented significant difference between two lines. In addition, the number of differentially expressed proteins with N deficiency treatment was almost twice as many as that with normal N treatment. It could be inferred that the insertion of Cry2A* in T2A-1 may bring about effects on carbon and nitrogen allocation and related metabolisms, especially under N deficiency environment.

No Effect of Bt-transgenic Rice on the Tritrophic Interaction of the Stored Rice, the Maize Weevil Sitophilus Zeamais and the Parasitoid Wasp Theocolax elegans

During Bt transgenic rice storage, Bt Cry1Ab/Cry1Ac fused protein is exposed to the maize weevil Sitophilus zeamais and the parasitoid wasp Theocolax elegans. We have carried out a long-term risk assessment for Bt rice to these non-target organisms in the storehouse. Effects of Bt rice on S. zeamais and T. elegans have been carefully detected in a laboratory experiment of over 5 years. The survival, development, fecundity, and longevity of the maize weevil were compared between Bt rice and non-Bt rice treatments for every 5 generations from generation 1 to 25. Moreover, the development, adult body size and sex ratio of T. elegans were compared between them parasitizing S. zeamais feeding on Bt rice or non-Bt rice. We found that although Bt Cry1Ab/Cry1Ac fused protein exists in the Bt rice grains and S. zeamais digestive tracts, Bt rice is not harmful to the maize weevil S. zeamais and its parasitoid T. elegans.

Effects of Cry1Ab-expressing Bt rice straw return on juvenile and adult Eisenia fetida

A 90 day experiment was conducted in the laboratory to investigate the potential effects of transgenic Cry1Ab-expressing rice (Bacillus thuringiensis (Bt) rice: T775 and its F1 hybrid) straw return on earthworm Eisenia fetida, compared to non-Bt rice (TYHZ) straw. Juvenile E. fetida could survive, grow up, mature and reproduce offspring well in a Bt rice treated test during the whole experiment. The significantly higher relative growth rate (RGR) was found in earthworms from Bt rice treatment than from non-Bt rice treatment on the 7th day. The period of sexual maturity for earthworms from Bt rice treatments was shortened significantly, compared to non-Bt rice treatments. Adult E. fetida survived with weight loss under Bt rice treatments. On the 7th and 15th day, earthworm RGR decreased and glutathione peroxidase (GSH-PX) activity increased under Bt rice straw treatments. Significantly fewer offspring were produced by earthworms from Bt rice than non-Bt rice treatments on the 60th and 75th day. Enzyme-linked immunosorbent assay (ELISA) determined a sharp decrease of Cry1Ab in straw mixed soil along with the experimental time, regardless of juvenile or adult earthworm treatments. Cry1Ab concentration in the earthworms from the juvenile group was significantly higher than those from the adult group. Bt rice straw return had significant effects on soil nutrients, especially on the content of total and available phosphorus. In view of two bioassays, Bt rice (T775 and its F1 hybrid) straw return presented different effects on E. fetida from the juvenile (no deleterious effect) and adult (a little negative effect) groups, that were not directly related to Cry1Ab presence and nutrient differences among the three rice variety treatments.

Resistance of transgenic rice events (rbcS:cry1Ac) against three lepidopteran rice pests

The transgenic rice expressing cry1Ac gene, which is linked to the rice rbcS promoter and its transit peptide sequence (tp), was highly resistant against all instars of Cnaphalocrocis medinalis (Guenetée) (Lepidoptera: Crambidae). In this study, we evaluated the larval mortality, behavior change, and field occurrence of three main rice pests, C. medinalis, Naranga aenescens (Moore) (Lepidoptera: Noctuidae), and Parnara guttata (Bremer & Grey) (Lepidoptera: Hesperiidae) in T4 generations of three Bt rice events (rbcS3:cry1Ac; 608102, 608104 and 608107) and non-Bt rice. All of the three Bt rice events were resistant to C. medinalis which showed significantly higher mortality for all instars compared to non-Bt rice. The resistance of Bt rice events against the larvae decreased gradually as the larvae developed. However, the survived larvae which ingested Bt rice events died eventually without further development. The resistance of three Bt rice events was investigated in the pot test, which was conducted with 3rd instars of C. medinalis, N. aenescens, and P. guttata, showed mortalities of over 70%. In behavioral assay, C. medinalis fed on the Bt rice events showed feeding avoidance and less leaf rolling behavior compared to that of the larvae fed on non-Bt rice. A 2-yr field survey conducted with larvae of C. medinalis and P. guttata also showed that the three Bt rice events significantly had lower damaged on leaves compared to that of non-Bt rice. Overall, the three Bt rice events were highly resistant to the larvae of lepidopteran target rice pests.

Toxicological and Biochemical Analyses Demonstrate the Absence of Lethal or Sublethal Effects of cry1C- or cry2A-Expressing Bt Rice on the Collembolan Folsomia candida.

Assessing the potential effects of insect-resistant genetically engineered (GE) plants on collembolans is important because these common soil arthropods may be exposed to insecticidal proteins produced in GE plants by ingestion of plant residues, crop pollen, or root exudates. Laboratory studies were conducted to evaluate the potential effects of two Bacillus thuringiensis (Bt)-rice lines expressing Cry1C and Cry2A in pollen and leaves and of their non-Bt conventional isolines on the fitness of the collembolan Folsomia candida and on the activities of its antioxidant-related enzymes, superoxide dismutase and peroxidase, and of its detoxification-related enzymes, glutathione reductase and glutathione S-transferase. Survival, development, reproduction, and the intrinsic rate of increase (rm) were not significantly reduced when F. candida fed on the Bt rice pollen or leaf powder than on the non-Bt rice materials; these parameters, however, were significantly reduced when F. candida fed on non-Bt rice pollen or non-Bt leaf-based diets containing the protease inhibitor E-64 at 75 μg/g. The activities of the antioxidant-related and detoxification-related enzymes in F. candida were not significantly affected when F. candida fed on the Bt rice materials, but were significantly increased when F. candida fed on the non-Bt rice materials containing E-64. The results demonstrate that Cry1C and Cry2A are not toxic to F. candida, and also indicate the absence of unintended effects on the collembolan caused by any change in plant tissue nutritional composition due to foreign gene transformation.

The Effects of Transgenic Bt Rice on Arthropod Community Structure During Storage

Effects of transgenic Bacillus thuringiensis (Bt) riceandnon-Bt riceonthe arthropodcommunity structure during storage were studied. Dried and cleaned grains (200 kg of F1 hybrid transgenic rice) from each rice variety were stored at unlidded ceramic pots (100 cm high, 80 cm diameter), and then stored in a 10-year-old barn. To investigate the species and number of arthropods using a needle-point sampler, each pot had 1 kg of grain sampled from both the upper layer (0–35 cm) and the lower layer (35–70 cm) every 15 days. The results showed 12 species of arthropods including Corrodentia, Acarina, Chelonethida, Lepidoptera, Coleoptera and Hymenoptera were found. No significant differences were observed in the community structure parameters of the arthropods between transgenic Bt rice and non-Bt rice. In both rice varieties, Liposcelis bostrychophilus exhibited the highest level of abundance of community structure, followed by Rhizopertha dominica and Tyrophagus putrescentiae. Overall, there was no significant ...

Assessing the effects of Cry1C rice and Cry2A rice to Pseudogonatopus flavifemur, a parasitoid of rice planthoppers

Transgenic rice producing insecticidal proteins from Bacillus thuringiensis (Bt) could help protect the plants from damage by lepidopteran pests. However, one concern is the potential of Bt rice to harm non-target natural enemies, which play a vital role in pest control. In the present study, the potential effects of Cry1C rice and Cry2A rice on different life-table parameters and population dynamics of Pseudogonatopus flavifemur, a parasitoid of rice planthoppers, were evaluated under laboratory and field condition. The exposure of P. flavifemur to plant-produced Bt proteins was also analyzed. Results indicated that direct feeding on rice plants was the main exposure pathway of P. flavifemur to the Cry1C and Cry2A proteins. No significant difference on the development, survival, longevity, fecundity, and prey consumption of P. flavifemur was detected over two generations between the Bt and non-Bt rice treatments. Furthermore, the population dynamics of P. flavifemur were not affected by Cry1C rice and Cry2A rice. In conclusion, the tested Cry1C rice and Cry2A rice do not appear to harm the parasitoid P. flavifemur.

Long-term cultivation of Bt rice expressing the Cry1Ab/1Ac gene reduced phytoparasitic nematode abundance but did not affect other nematode parameters in paddy fields

The uncertainty of ecological risks and the effects of growing transgenic Bt rice on the environment hamper its commercial production. Here, soil nematode communities were used as an indicator of soil health and soil food web structure to evaluate the potential effects of growing Bt rice without chemical insecticides for 3years in the paddy field. The nematodes and soil physicochemical properties of Bt rice fields were compared to the near-isogenic control, non-Bt rice fields. A total of 108,363 specimens belonging to 28 different genera were enumerated. The Hirschmanniella, Tobrilus, Dorylaimus and Filenchus were dominant genera. A three-year paddy rice cultivation of Bt rice (Huahui 1) negatively affected the abundance of phytoparasitic nematodes but did not affect the total number of nematodes, the abundance and relative abundance of free-living nematodes, genera richness, diversity indices, soil food web conditions, or community compositions. However, apparent seasonal and inter-annual changes in these variables were observed, indicating that the impact of environmental factors was more stronger than that of the Bt toxin. In conclusion, the potential ecological risks of Bt rice on soil health and sustainability warrant further research to disentangle the impacts from various confounding environmental factors.

Transcriptomic response of wolf spider, Pardosa pseudoannulata, to transgenic rice expressing Bacillus thuringiensis Cry1Ab protein

BackgroundBacillum thuringiensis (Bt) toxin produced in Cry1-expressing genetically modified rice (Bt rice) is highly effective to control lepidopteran pests, which reduces the needs for synthetic insecticides. Non-target organisms can be exposed to Bt toxins through direct feeding or trophic interactions in the field. The wolf spider Pardosa pseudoannulata, one of the dominant predators in South China, plays a crucial role in the rice agroecosystem. In this study, we investigated transcriptome responses of the 5th instar spiders fed on preys maintained on Bt- and non-Bt rice.ResultsComparative transcriptome analysis resulted in 136 differentially expressed genes (DEGs) between spiderlings preying upon N. lugens fed on Bt- and non-Bt rice (Bt- and non-Bt spiderlings). Functional analysis indicated a potential impact of Bt toxin on the formation of new cuticles during molting. GO and KEGG enrichment analyses suggested that GO terms associated with chitin or cuticle, including “chitin binding”, “chitin metabolic process”, “chitin synthase activity”, “cuticle chitin biosynthetic process”, “cuticle hydrocarbon biosynthetic process”, and “structural constituent of cuticle”, and an array of amino acid metabolic pathways, including “alanine, asparatate and glutamate metabolism”, “glycine, serine and theronine metabolism”, “cysteine and methionine metabolism”, “tyrosine metabolism”, “phenylalanine metabolism and phenylalanine”, and “tyrosine and tryptophan biosynthesis” were significantly influenced in response to Cry1Ab.ConclusionsThe Cry1Ab may have a negative impact on the formation of new cuticles during molting, which is contributed to the delayed development of spiderlings. To validate these transcriptomic responses, further examination at the translational level will be warranted.