Transgenic Insect-resistant Cotton Research Articles

Deletion of the 3′ End of the Introduced cry1Ac Gene Retains the Insecticidal Activity in Transgenic Cotton

The structure and expression of exogenous genes in transgenic crops are critical for the target traits. R7569 has the same exogenous insertion structure as the transgenic insect-resistant cotton MON531 but with a deletion in the 3′ end of the cry1Ac gene and the terminator region. Thus, in the present study, transcription, expression, and insecticidal activity assays were conducted to determine the function of the truncated cry1Ac gene. R7569 has a truncated cry1Ac gene with a length of 2554 bp encoding 881 amino acids, and the transcription termination site was mainly concentrated downstream of the truncated position and extended 160–270 bp from the truncated position using rapid amplification of cDNA ends (RACE). The transcript levels of the cry1Ac gene in R7569 were significantly higher than those of MON531 implants, except for during the boll stage. The content of the Cry1Ac protein in R7569 was higher than that of MON531 in the cotton leaf in all three periods. The corrected mortality rates of R7569 and MON531 against bollworms were 93.09% and 88.83%, respectively. The LC50 value of R7569 was 0.732 ng/g (dw), indicating a high level of resistance to bollworm. In this study, for the first time, we found a partial deletion of the target gene in commercially applied transgenic crops, and the partial deletion of the 3′ end of the cry1Ac gene retained a better transcription, expression level, and insecticidal activity, which can provide a specific case for the safety evaluation of transgenic crops.

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

Effects of transgenic insect-resistant Bt cotton Zhongkangza 5 and Lumianyan 23 and Bt + CpTI cotton sGK958 and Zhongmiansuo 45 on Tetranychus cinnabarinus growth and reproduction were compared with those of nontransgenic cotton (K836) under laboratory conditions. Developmental times of different T. cinnabarinus stages fed on transgenic Bt and Bt + CpTI cotton differed significantly from those fed on K836. Pre-oviposition (1.44 d) and oviposition (12.71 d) periods and female life span (14.11 d) were longer on K836 than on transgenic cotton. Maximum fecundity was 75.61 eggs per female on K836, while minimum fecundity was 54.68 eggs per female on sGK958. Net reproductive rate was highest with 55.00 female offspring on K836, whereas the lowest was 37.219 female offspring on Zhongkangza 5. The highest intrinsic rate of increase was 0.454 day−1 on K836, whereas the lowest was 0.246 day−1 on Zhongkangza 5. The highest finite rate of increase was 1.575 day−1 on K836, whereas the lowest was 1.278 day−1 on Zhongkangza 5. The shortest population doubling time was 1.526 d on K836, while the longest was 2.823 d on Zhongkangza 5. Thus, transgenic cotton inhibited T. cinnabarinus development and reproduction, indicating transgenic cotton could prevent damage by T. cinnabarinus or other pests.

Molecular profiling of resistance alleles in Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae) collected from different locations

BackgroundAfter the commercialization of insect-resistant transgenic Bt cotton Bollgard I & II, India ranks first in the world in cotton production. Cotton insecticide consumption was drastically reduced as nearly 95% of the cotton area was replaced with Bollgard II. However, the benefits of transgenic cotton appear to have been diminished as the pink bollworm, Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae) developed field resistance to Cry1Ac expressing Bt cotton in India in 2008. In 2015, there was an unusual survival of P. gossypiella on Bollgard II cotton in some parts of Gujarat and Maharashtra, which is a cause for concern.ResultsIn the present study, PCR analysis and gel visualization of BGII resistant field population of P. gossypiella showed that the presence of r1, r2, r3, r1s, r2s, r3s, and ss mutated cadherin alleles, which produced amplicon sizes of 750 bp, 700 bp, 730 bp, 12,700 bp, 750 bp, 980 bp, 600 bp and 1600 bp, respectively, when seven different types of cadherin allele(s) specific primers were used. The r1 mutant allele was detected in Amaravati, Wardha, Yavatmal, and Nagpur, but not in Akola and Buldhana, using primers r1disfor and Int-540. The r2 mutant allele was detected in Akola, Wardha, and Nagpur, but not in Buldhana, Amaravati, and Yavatmal, using primers r2disback and Cad2366. The r3 mutant allele was detected in all locations using primers r3disback and Cad3221. Amplicons of sizes 750 bp, 700 bp and 730 bp were obtained for r1, r2, and r3 mutant alleles, respectively. The sizes of the amplicons were 1270 bp for r1s, 750 bp for r2s, and 980 bp for r3s.The absence of bands for r1, r2, and r3 cadherin alleles in individuals indicated the possibility of having the ss allele, which was confirmed using primers Cad3324 and Int-651. The presence of ss mutant allele was observed in field-collected P. gossypiella populations from BG II cotton in various locations, with a 600 bp and 1600 bp size amplicons produced using the same primers.ConclusionsPCR analysis revealed the presence of r1, r2, r3, r1s, r2s, r3s, and ss mutated cadherin alleles in field-collected populations of Vidarbha which provide evidence to field-evolved resistance of P. gossypiella to BGII cotton.

Impact of two neonicotinoid insecticides on the parasitoids of Apolygus lucorum: Peristenus spretus and Peristenus relictus

With the widespread planting of transgenic Bt insect-resistant cotton, non-target mirid bug Apolygus lucorum (Meyer-Dür) has been transformed from a secondary problem to a major pest. The parasitoids Peristenus spretus (Chen et van Achterberg) and Peristenus relictus (Ruthe) can provide effective control of A. lucorum and potential for broad application. In this study, we determined the effects of imidacloprid and acetamiprid on adults of these parasitoids using the dry film residual contact method. The effects of different concentrations of both insecticides on the survival and reproduction of the adult parasitoids and lethal concentrations (LC50) were also determined. We found that the two neonicotinoid insecticides had negative effects on the parasitoid adults, and P. spretus was more sensitive to the insecticides. Higher concentrations of these insecticides had greater negative effects on the survival and reproduction of the adult parasitoids. The insecticides reduced the level of detoxification enzyme activity in P. spretus (except MFO, for which there was no significant change), but induced higher levels of detoxification enzyme activity in P. relictus. These findings suggest that chemical control using imidacloprid and acetamiprid is not compatible with biological control from these parasitoids, especially P. spretus. This study provides a theoretical basis for improvement of integrated management of A. lucorum.

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.

Determining Pollen-Mediated Gene Flow in Transgenic Cotton.

Gene flow is one of the major concerns associated with the release of transgenic plants into the environment. Unrestricted gene flow can results in super weeds, reduction in species fitness and genetic diversity, and contamination of traditional plants and foods. Thus, it is important and also necessary to evaluate the extent of gene flow in the field for transgenic plants already released or being considered for a release. Transgenic cotton is among the first transgenic crops for commercialization, which are widely cultivated around the world. In this chapter, we use transgenic insect-resistant cotton and herbicide-tolerant cotton as two examples to present a field practice method for determining transgene flow in cotton. The procedure includes three major sections: (1) field design, (2) seed collection, and (3) field and lab bioassay.

Development of Insect-Resistant Transgenic Cotton with Chimeric TVip3A* Accumulating in Chloroplasts.

An optimized vip3A gene, designated as vip3A*, was chemically synthesized, and a chloroplast transit peptide sequence of thi1 gene was attached to its 5' end to produce the tvip3A*. vip3A* and tvip3A* genes were transformed into Gossypium hirsutum cv. Zhongmiansuo35 mediated by Agrobacterium tumefaciens. Four independent transgenic T1 lines with single-copy insertions and comparable phenotypes (CTV1 and CTV2 for tvip3A*, and CV1 and CV2 for vip3A*) were selected by polymerase chain reaction (PCR), reverse transcription (RT)-PCR, Southern blotting, enzyme-linked immunosorbent assay (ELISA), and insect bioassay. As expected, the Vip3A* protein of CTV1 and CTV2 were transported to the chloroplasts, where they accumulated. Our results suggest that the two tvip3A* transgenic lines, CTV1 and CTV2, can directly develop insect-resistant cultivars and could be used as a resource for raising multi-toxin-expressing transgenic cotton.

Expression of GNA and biting site-restricted cry1Ac in cotton; an efficient attribution to insect pest management strategies

Insect-resistant transgenic cotton has been commercialized for two decades. Most of the introduced cultivars express Bt gene(s) constitutively under the control of 35S promoter in whole-plant tissues. However, there have been other promoters considered by researchers to confine the toxin expression to targeted organ and tissues. We developed a triple-gene construct including GNA, cry1Ac and cp4 epsps genes. We attempted to confine cry1Ac expression to insect biting sites by cloning it to downstream of a wound-inducible promoter isolated from Asparagus officinalis (AoPR1). Moreover, to broaden the range of resistance, GNA was driven by the 35S promoter to target the sap-sucking insects like aphids which impose large losses in cotton production. To select the transformants in selection medium and for glyphosate tolerance, GNA and cry1Ac genes were accompanied with cp4 epsps gene. Two binary vectors harboring desired genes were constructed and utilized in the study (pGTGNAoC1AC and pGTGN35C1AC). Transformation of cultivar GSN-12 was carried out by employing Agrobacterium tumefaciens strain EHA105. Plantlets were primarily screened under glyphosate (N-phosphonomethyl glycine) selection pressure and subsequently subjected to molecular and biotoxicity assays. Introduction of cry1Ac and GNA to cotton plant conferred resistance to Spodoptera littoralis and Aphis gossypii Glover. Restriction of cry1Ac toxin protein to insect biting sites along with a plant lectin attributes significantly to insect pest management strategies.

Inhibition of Fusarium solani in transgenic insect-resistant cotton plants treated with silver nanoparticles from Prosopis glandulosa and Pluchea sericea

The phytosynthesis of nanoparticles is a green chemistry approach that combines nanotechnology and bioactive compounds of plants. The aim of this study was to evaluate the effect of silver nanoparticles (AgNPs) from Prosopis glandulosa and Pluchea sericea, respectively, on the control of Fusarium solani previously inoculated in the rhizosphere of transgenic insect-resistant cotton plants. The results showed that the weekly application of AgNPs from P. glandulosa and P. sericea caused a diminution of fungal propagules in the soil after 30 days of treatment. In this sense, the AgNPs from P. glandulosa were more efficient in the reduction of infection points in the roots of the plants infected with F. solani compared with AgNPs from P. sericea. Additionally, the application of AgNPs from both plants showed a significant increase of optimum quantum yield (Fv/Fm), stomata conductance (gs), and the number of lateral roots in transgenic insect-resistant cotton plants after 30 days of exposure when compared to the control. Based on our results, AgNPs from P. glandulosa and P. sericea could inhibit growth of Fusarium solani. However, more extensive and elaborate studies are needed to explain the different mechanisms that participate in the inhibition of growth of fungus using nanoparticles from these plants.

Developing Bisexual Attract-and-Kill for Polyphagous Insects: Ecological Rationale versus Pragmatics.

We discuss the principles of bisexual attract-and-kill, in which females as well as males are targeted with an attractant, such as a blend of plant volatiles, combined with a toxicant. While the advantages of this strategy have been apparent for over a century, there are few products available to farmers for inclusion in integrated pest management schemes. We describe the development, registration, and commercialization of one such product, Magnet(®), which was targeted against Helicoverpa armigera and H. punctigera in Australian cotton. We advocate an empirical rather than theoretical approach to selecting and blending plant volatiles for such products, and emphasise the importance of field studies on ecologically realistic scales of time and space. The properties required of insecticide partners also are discussed. We describe the studies that were necessary to provide data for registration of the Magnet(®) product. These included evidence of efficacy, including local and area-wide impacts on the target pest, non-target impacts, and safety for consumers and applicators. In the decade required for commercial development, the target market for Magnet(®) has been greatly reduced by the widespread adoption of transgenic insect-resistant cotton in Australia. We discuss potential applications in resistance management for transgenic cotton, and for other pests in cotton and other crops.

Effects of insect-resistant transgenic cotton on ground-dwelling beetle assemblages (Coleoptera)

AbstractWe compared the ground-dwelling beetle assemblages under four scenarios in which transgenic Bt (Cry 1Ac) cotton (33B), transgenic Bt (Cry 1Ac)+CpTI cotton (SGK321), conventional cotton (33), conventional cotton (Shiyuan 321) in North China. During the survey in two years (2009–2010), 24 ground beetle species were captured with pitfall traps in 20 plots which included five replicates for each cotton type. No significant difference was observed in the number of ground beetle species captured, activity density, evenness and Shannon-Wiener diversity among the four cotton varieties. Chlaenius posticalis was less abundant in transgenic Bt+CpTI cotton (SGK321) fields than its conventional cotton (Shiyuan 321), but more abundant in transgenic Bt cotton (33B) fields compared with its conventional cotton (33). There was no significant difference for other abundant species between in transgenic cotton and in conventional cotton fields. Based on non-metric multidimensional scaling (NMDS) analysis, ground-dwelling beetle assemblages were similar in transgenic and conventional cotton over the two years, but the ground-dwelling beetle assemblages in transgenic cotton 33B significantly differed from that in the conventional cotton (strain 33) in 2010. No strong evidence that the transgenic cotton effect on ground-dwelling beetle assemblages was found in this study.

Productivity and profitability of cotton–wheat system as influenced by relay intercropping of insect resistant transgenic cotton in bed planted wheat

Abstract Cotton ( Gossypium hirsutum L.) is the leading cash crop being grown across the globe including Pakistan. By the inclusion of insect resistant transgenic cotton ( BT cotton), the cotton production has mounted many folds in Pakistan. BT cotton is mostly grown in Southern Punjab in cotton – wheat cropping system of Pakistan; however there exists a time conflict among wheat harvest and BT cotton sowing in this system. Wheat is harvested during late April but the ideal sowing time of BT cotton is early-mid March indicating a time conflict of 4 – 6 weeks which is becoming the main concern leading to wheat exclusion from this system. Intercropping of BT cotton in standing wheat is one of the possible options to manage this overlapping period. This two year field study was, therefore, conducted at two locations (Multan, Vehari) to evaluate the economic feasibility of relay intercropping of BT cotton through different sowing methods in BT cotton – wheat cropping system. BT cotton – wheat cropping systems included in the study were: conventionally tilled cotton (CTC) on fallow land during early and late March, CTC during late April after harvest of flat sown wheat (FSW), bed sown wheat (BSW) + intercropped cotton during early and late March, and ridge sown wheat (RSW) + intercropped cotton during early and late March. Planting cotton in fallow land with conventional tillage during early March had more seed cotton yield; whereas planting in the same way during April after wheat harvest had minimum seed cotton yield. Likewise, FSW had more yield than ridge and bed sown wheat with intercropped BT cotton during early or late March. However, the system productivity in terms of net income, benefit: cost ratio and marginal rate of return of BSW + intercropped BT cotton during early March was the highest during both years at both locations. However, the system with sole crop of BT cotton sown on fallow land during late or early March was the least economical even than the system with CTC during late April after harvest of FSW. In conclusion, BSW + intercropped cotton during early March may be opted to manage the time conflict and improve the economic productivity of BT cotton – wheat cropping system without wheat exclusion from the system.

A rapid loop-mediated isothermal amplification method for detection of the modified GM cry1A gene in transgenic insect-resistant cotton and rice

Among the commercial genetically modified (GM) crops, the insect-resistant GM crops are the major cultivars that cry gene is introduced into. A cry1Ab/1Ac GM fusion gene (GFM cry1A) and a GM truncated cry1Ac gene (cry1Ac-Mon) is the key foreign gene employed for construction of GM crops by China researchers and Monsanto Technology LLC respectively. Here these two genes are entitled “GM cry1A” gene and a rapid visual loop-mediated isothermal amplification (LAMP) assay method for detection of GM cry1A in transgenic insect-resistant crops was established. The LAMP assay was performed at an optimal temperature of 65 °C for 60 min in the presence of a set of four specific primers recognized six distinct sequences of the GM cry1A gene. The rough detection limit to the GM cry1A in samples is as low as 0.01% (a weight ratio of transgenic insect-resistant rice/cotton to non-transgenic rice/cotton). Comparatively, the sensitivity of this LAMP method is 10 times over that of the conventional PCR method. Fifteen cultivars/events and five Bt strains with or without cry1A gene were analyzed using the LAMP method as well as PCR method. The results demonstrate that this LAMP method shows a distinct specificity to the GM cry1A gene comparing with PCR analysis. Therefore, this LAMP method will be a potential effective tool for screening the GM cry1A gene in GM crops which are widely plant in China and other developing countries.

Impacts of transgenic poplar-cotton agro-ecosystems upon target pests and non-target insects under field conditions.

Poplar-cotton agro-ecosystems are the main agricultural planting modes of cotton fields in China. With increasing acres devoted to transgenic insect-resistant poplar and transgenic insect-resistant cotton, studies examining the effects of transgenic plants on target and non-target insects become increasingly important. We systematically surveyed populations of both target pests and non-target insects for 4 different combinations of poplar-cotton eco-systems over 3 years. Transgenic Bt cotton strongly resisted the target insects Fall webworm moth [Hyphantria cunea (Drury)], Sylepta derogata Fabrieius, and American bollworm (Heliothis armigera), but no clear impact on non-target insect cotton aphids (Aphis gossypii). Importantly, intercrops containing transgenic Pb29 poplar significantly increased the inhibitory effects of Bt cotton on Fall webworm moth in ecosystem IV. Highly resistant Pb29 poplar reduced populations of the target pests Grnsonoma minutara Hubner and non-target insect poplar leaf aphid (Chaitophorus po-pulialbae), while Fall webworm moth populations were unaffected. We determined the effects of Bt toxin from transgenic poplar and cotton on target and non-target pests in different ecosystems of cotton-poplar intercrops and identified the synergistic effects of such combinations toward both target and non-target insects.

Molecular identification of Fusarium species isolated from transgenic insect-resistant cotton plants in Mexicali valley, Baja California.

Cotton production in the Mexicali valley is adversely affected by wilt and root rot disease associated with Fusarium species. In the present study, we sought to isolate and identify the Fusarium species in the rhizosphere of transgenic insect-resistant cotton plants grown in the Mexicali valley. Our analyses isolated four native fungi from the rhizosphere of cotton plants, namely, T-ICA01, T-ICA03, T-ICA04, and T-ICA08. These fungal isolates were categorized as belonging to Fusarium solani using their phenotypic characteristics and ITS region sequence data. Examination of the infection index showed that T-ICA03 and T-ICA04 caused systemic colonization (90%) of seeds followed by the occurrence of radicle and coleoptile decay. In contrast, T-ICA08 strain was less pathogenic against seed tissues (40%) in comparison to the other strains isolated. Our study showed that in transgenic insect-resistant cotton the disease "Fusarium wilt" is caused by the fungus, F. solani. Future studies are necessary to characterize the F. solani populations to determine whether phenological stages might influence the genetic diversity of the fungal populations present.

Crop dominance exerts specific effects on foliage-dwelling arthropods inBacillus thuringiensiscotton

Shifts in crop composition in an agro-ecosystem may have profound effects on plant-associated arthropods. The widespread adoption of transgenic insect-resistant cotton expressing insecticidal toxins Cry1A from Bacillus thuringiensis (Bt) has caused a dramatic shift in agricultural landscapes over the last 15 years, thus raising concerns about the potential impacts of Bt crops on nontarget organisms worldwide. The potential effect of crop composition shift as a result of the increasing acreage of Bt cotton on an arthropod community was assessed at three levels (0%, 75% and 100%) of Bt dominance in a 2-year field trial in northern China. Three findings confirmed that the arthropod assemblage of a certain field was influenced by crop composition and its developmental stage: (i) the proportion of Bt cotton in the crop mixture consistently affected the abundance of pests, natural enemies and total arthropods; (ii) bootstrap methods demonstrated significant effects of Bt cotton on species richness, diversity and evenness; and (iii) non-metric multidimensional scaling analysis showed that the arthropod community of a certain agricultural ecosystem varied with crop composition and plant developmental stage. The findings of the present study may have significant implications for cotton pest management with respect to transgenic Bt cotton, highlighting the potential of conservation biological control via the combination of an appropriate crop genetic ratio and timely chemical control.

Impacts of the transgenic CrylAc and CpTI insect-resistant cotton SGK321 on selected soil enzyme activities in the rhizosphere

Transgenic CrylAc and CpTI insect-resistant cotton SGK321 is widely adopted for many years in several regions of China, however the understanding of its potential effects on soil enzyme activities is not studied. The impacts of transgenic cotton SGK321 on dehydrogenase, urease and phosphatase activities in rhizosphere soil were investigated in a two-year field study in Northern China. Rhizosphere soil enzyme activities between transgenic cotton SGK321 and its non-transgenic parental cotton Shiyuan 321 were found to differ at senescence. However compared to the plant growth stages and cotton cultivar, the impacts of the transgenic trait were minor or transient. The principal component analysis also showed no significant or minor difference in the activities of dehydrogenase, urease and phosphatase in the rhizosphere soil of transgenic cotton SGK321 and its counterpart. Our results indicated that the transgenic cotton SGK321 has no apparent impact on dehydrogenase, urease and phosphatase activities in rhizosphere soil.

Qualitative and Quantitative PCR-Based Detection Methods for Authorized Genetically Modified Cotton Events in India.

Qualitative diagnostics for all five commercialized genetically modified (GM) cotton events for insect resistance in India is being reported for the first time in this paper. The cost-effective and robust multiplex PCR (MPCR)-based detection assay, distinguishing the insect resistant transgenic Bt cotton events, viz., MON531, MON15985, Event 1, GFM-cry1A, and MLS-9124, has been developed. This decaplex PCR assay targets nine transgenic elements, viz., sequences of four transgenes, three transgene constructs, and two event-specific sequences along with one endogenous reference gene. The LOD of the qualitative MPCR assay was up to 0.1%. A quantitative detection method for four widely commercially cultivated GM cotton events, namely, MON531, MON15985, Event 1, and GFM-cry1A, covering 99.5% of the total area under GM cultivation in the country, is also reported. A construct-specific real-time PCR assay has been developed for quantification of these GM cotton events with LOQ <0.05% and LOD <0.025%. The developed assays will be of great use to screen for the presence/absence of authorized GM cotton events in unknown samples and to check the authenticity of GM cotton seed samples.

Effects of the transgenic CrylAc and CpTI insect-resistant cotton SGK321 on rhizosphere soil microorganism populations in northern China

Transgenic CrylAc and CpTI insect-resistant cotton SGK321 has been widely adopted for many years in several regions of China, however the understanding of its potential effects on soil microorganisms is limited. The impact of transgenic cotton SGK321 on microorganism populations in rhizosphere soil was investigated. The numbers of bacteria, fungi, and actinomycetes were measured by counting colony-forming units after incubation on appropriate medium in a two-year field study in the northern China. Rhizosphere soil microorganism populations between transgenic cotton SGK321 and its non-transgenic parental cotton or conventional cotton were different at some plant growth stages and/or in some years. However compared to the plant growth stage and cotton cultivar, the impacts of the transgenic trait were slight or transient. The principal component analysis also showed no significant or minor difference in the numbers of bacteria, fungi, and actinomycetes in rhizosphere soil between transgenic cotton SGK321 and its non-transgenic parental cotton. These results suggest that the transgenic cotton SGK321 has no apparent impact on microorganism populations in rhizosphere soil.

Impact of Single and Stacked Insect-Resistant Bt-Cotton on the Honey Bee and Silkworm

Transgenic insect-resistant cotton (Bt cotton) has been extensively planted in China, but its effects on non-targeted insect species such as the economically important honey bee (Apis mellifera) and silkworm (Bombyx mori) currently are unknown. In this study, pollen from two Bt cotton cultivars, one expressing Cry1Ac/EPSPS and the other expressing Cry1Ac/Cry2Ab, were used to evaluate the effects of Bt cotton on adult honey bees and silkworm larvae. Laboratory feeding studies showed no adverse effects on the survival, cumulative consumption, and total hemocyte count (THC) of A. mellifera fed with Bt pollen for 7 days. No effects on the survival or development of B. mori larvae were observed either. A marginally significant difference between Cry1Ac/Cry2Ab cotton and the conventional cotton on the THC of the 3rd day of 5th B. mori instar larvae was observed only at the two highest pollen densities (approximately 900 and 8000 grains/cm2), which are much higher than the pollen deposition that occurs under normal field conditions. The results of this study show that pollen of the tested Bt cotton varieties carried no lethal or sublethal risk for A. mellifera, and the risk for B. mori was negligible.