Transgenic Cotton Varieties Research Articles

Low temperature exposure influences nitrogen metabolism resulting in decreased Cry1Ac insecticidal endotoxin content in cotton seeds

BackgroundSudden temperature drops, resulting from extreme weather events, often occur during the boll-setting period of cotton in Xinjiang, China, causing decreased expression of Bacillus thuringiensis (Bt) insecticidal proteins in cotton bolls. The precise threshold temperatures and durations that lead to significant changes in Cry1Ac endotoxin levels under low temperatures remain unclear. To address this, we investigated the effects of different temperatures and stress durations on Cry1Ac endotoxin levels in cotton bolls. In 2020–2021, two Bt transgenic cotton varieties, conventional Sikang1 and hybrid Sikang3, were selected as experimental materials. Various low temperatures (ranging from 16 to 20 °C) with different durations (12 h, 24 h and 48 h) were applied during the peak boll-setting period.ResultsAs the temperature decreased, the Cry1Ac endotoxin content in the boll shell, fiber, and seed exhibited a declining trend. Moreover, the threshold temperature which caused a significant reduction in Cry1Ac endotoxin content increased with the prolonged duration of low-temperature stress. Among the components of cotton bolls, seeds were most affected by low-temperature stress, with the threshold temperature for a significant reduction in Cry1Ac endotoxin content ranging from 17 °C to 19 °C. Correlation analysis indicated that low temperatures led to a decrease in protein synthesis capacity and an increase in degradation ability, resulting in reduced Cry1Ac endotoxin content. Pathway analysis revealed that both free amino acid and peptidase had significant negative effects on Cry1Ac endotoxin content.ConclusionIn summary, when the daily average temperature was ≤ 19 °C, implementing cultural practices to reduce free amino acid content and peptidase activity could serve as effective cold defense strategies for Bt cotton production.

Impact Analysis of Biorational Insecticides under Weeded and Non Weeded Habitat on Whitefly, Bemisia tabaci Management in Cotton Agroecosystem

Transgenic Bt cotton is effective to a high degree of, with respect to target lepidoptran bollworms, however sucking pests especially whitefly posed a serious issues in absence of bollworm in genetically modified (GM) crops. Therefore, to understand the efficacy of various biorational compounds against whitefly under non-weedy as well as weedy field conditions, studies on whitefly carried out during kharif 2018, to know the changes in number of whitefly adults as well as nymphs. Transgenic hybrid cotton variety RCH 650 was sown with a spacing of 100×45 cm and replicated four times in both non-weedy and weedy habitat. Although, standard check Dimethoate 30 EC proved it’s efficacy after first and second spray in cotton crop against whitefly. Not with standing, after the application of biorational first time as spray in 29th Standard Meteoroloical Week (SMW), Nimbecidine 300 ppm was admitted as most effective in non-weedy (66.76 and 60.65% mean mortality in whitefly adult and nymph, respectively) as well as in weedy habitat that caused 56.77 and 55.54% mean mortality in adult and nymph, respectively over a period of seven days after application. Entomopathogenic fungi Verticillium lecanii found better to control whitefly adults (42.06 and 40.63%), while Metarhizium anisopliae (42.39 and 36.01%) found more effective for nymphal mortality in non-weedy as well as in weedy habitat. One and same pattern of efficacy of biorational was reconstructed against whitefly again after second application of biorational in all the treatment selected to test against whitefly.

Susceptibility of Fall Armyworm Field Populations to Vip3Aa/Cry Bt Maize in a Tropical Agricultural Region

Fall armyworm (FAW, Spodoptera frugiperda) is a polyphagous and migratory lepidopteran pest insect in field crops and is notoriously invasive worldwide. In large portions of the Americas, its populations are managed using transgenic maize or cotton varieties producing insecticidal proteins from Bacillus thuringiensis (Bt), primarily Vip3Aa pyramided with Cry Bt proteins. We determined the susceptibility of FAW field populations from locations pressured with such maize hybrids for over five years. We used time–mortality bioassays with F1 third-instar larvae of six geographically distinct populations collected in maize fields of a tropical agricultural region encompassing four Brazilian states. We maintained the neonate progeny from the field populations on an artificial diet until the third instar, and then determined their survival curves on the foliage of three Vip3Aa/Cry-producing Bt maize hybrids. Death of the mid-size, third-instar FAWs occurred relatively rapidly, with larval mortality rates reaching 98–100% in less than five days regardless of Bt maize hybrid. However, median survival time (ST50) for the larvae differed among the populations, with the lowest and highest ST50 values occurring for PI-Cr (42 h, 1.75 d) and PI-Ur populations (66–90 h, 2.75–3.75 h), respectively. Therefore, the F1 third-instar larvae of FAW populations were largely susceptible to Vip3Aa/Cry-producing maize foliage, and the most contrasting susceptibility occurred in the insects from Piauí state, Brazil. These results indicate that progeny of FAWs from areas highly pressured with Vip3Aa/Cry Bt maize hybrids are killed on maize foliage producing Vip3Aa and Cry Bt proteins despite field reports of increased leaf damage by the larvae in some locations. This research informs decision making for Bt-crop resistance management by producers, technicians, and researchers in local, regional, and world agriculture.

From genes to fields: Environmental compatibility of herbicide tolerant transgenic cotton

IntroductionThere are several enticing reasons to use genetic engineering to develop transgenic cotton plants with economically relevant new traits. The use of transgenic cotton to protect crops from biotic stressors like weeds may prove to be a cost-effective solution. ObjectivesThe development of herbicide-resistant cotton variants is the primary motivation for gene transfer in this crop. In the current study, we conducted a battery of experiments on the herbicide-tolerant cotton variety MNH-786 to investigate its expression patterns and environmental adaptation. Material and methodsThe 35S promoter controls the expression of the codon-optimized Cp4-EPSPS gene that is present in this variety. Several different molecular approaches, such as polymerase chain reaction (PCR), Florescent In-Situ Hybridization analysis, and enzyme-linked immunosorbent assay (ELISA), are used to confirm the presence of transgenic cotton plants. The glyphosate spray assay was performed using molecular analysis, employing a dosage of 2000 ml per acre. The suitability of transgenic and non-transgenic cotton plants in four unique environments—the Multan, Vehari, Bahawalpur, and Faisalabad Districts of Punjab province, Pakistan was assessed using a comparative comparison. A gene x environment interaction (GEI) biplot was used to analyze the correlation between genes and their environments. ResultsTransgenic cotton plants screened using PCR to target 1.467 kb regions showed effective integration into cotton genomes. Results showed that Cp4-EPSPS proteins fluctuated and associated with environmental variables across all three generations (T0, T1, and T2). In the herbicide spray assay, all transgenic cotton plants survived, but non-transgenic cotton and all weeds died. According to the "which-won-where" polygon, transgenic cotton plant Events 3, 4, 5, 6, and 7 performed better in three settings, except Faisalabad. According to correlation and heat-map yield research, transgenic cotton variety MNH-786 Events 4, 5 and 6 have a higher consistency and influence in Vehari district's natural habitats. Multan and Bahawalpur also show encouraging results. In Faisalabad, no transgenic events perform well. ConclusionWe conclude that Events 4 and 5 show a substantial abundance of genetic potential that is robust over a wide range of environments thanks to our thorough study of the outcomes obtained under these conditions. SignificanceOur study emphasises the importance of transgenic cotton, its performance, and its exposure to appropriate agroecological zones. This knowledge can be advantageous for farmers in attaining optimal conditions to maximize productivity.

Differentiation of the Pathotypes in Race 29 of cotton Bacterial Leaf Blight Pathogen Xanthomonas axonopodis pv. malvacearum (Xam) and the reaction of some transgenic ( Bt ) and non-transgenic cotton varieties grown in Vidharbha region to the prevalent Xam races and pathotypes.

Differentiation of the Pathotypes in Race 29 of cotton Bacterial Leaf Blight Pathogen Xanthomonas axonopodis pv. malvacearum (Xam) and the reaction of some transgenic ( Bt ) and non-transgenic cotton varieties grown in Vidharbha region to the prevalent Xam races and pathotypes.

Response of pink bollworm Pectinophora gossypiella (Saunders) to Cry1Ac and Cry2Ab toxin

BackgroundDuring field surveillance in Gujarat, India, in 2009, scientists found that pink bollworm was surviving in the first generation of Bollgard cotton, which contains a single protein. This survival was observed in four districts of Gujarat. From 2012 to 2014, surveys revealed that pink bollworm larvae had higher survival rates on Bollgard II cotton in Amreli and Bhavnagar districts. In 2016, a pink bollworm outbreak in Maharashtra caused significant losses in cotton production, leading to damage, yield losses, and increased management costs in several regions. The objective of the present study was to determine the reaction of Pectinophora gossypiella to Cry1Ac and Cry2Ab toxins.ResultsNeonates of P. gossypiella collected from six distinct locations in Vidarbha were subjected to seven different concentrations of Cry1Ac. The highest LC50 value was recorded in the population collection of Yavatmal (1.362 μg/ml diet) but the lowest LC50 value of 0.600 μg/ml diet in Buldana population. The highest MIC50 value was recorded in the population collected from Yavatmal (0.743 μg/ml diet) and the lowest MIC50 value of 0.413 μg/ml diet in the Buldana population (0.431 μg/ml diet). The highest IC50 value was recorded in the population collected from Yavatmal (0.303 μg/ml diet) but the lowest IC50 value of 0.127 μg/ml diet in the Buldana population. Neonates of P. gossypiella collected from six different locations in Vidarbha were exposed to seven different concentrations (9.0, 3.0, 1.0, 0.333, 0.111, 0.037 and 0.012 for Cry1Ac and 27.0, 9.0, 3.0, 1.0, 0.333, 0.111 and 0.037 μg/ml for Cry2Ab) which revealed that the Yavatmal population had the highest LC50 value of 94.294 μg/ml diet and the lowest LC50 value was recorded in the Amravati population (42.144 μg/ml diet). The highest MIC50 value of 27.258 μg/ml diet was recorded in Buldana population, but the lowest MIC50 value was recorded in the Amravati population (12.881 μg/ml diet). The highest IC50 value of 3.209 μg/ml diet was observed in Yavatmal population, and the lowest one was recorded in the Amravati population (1.574 μg/ml diet).ConclusionsAccording to the LC50 values, all of the P. gossypiella populations in Vidarbha were extremely insensitive and had field-evolved resistance to the Bt proteins found in the transgenic cotton varieties of Bollgard II.

Resistance of Cabbage Loopers to Bacillus thuringiensis (Bt) Toxin Cry1F and to Dual-Bt Toxin WideStrike Cotton Plants.

The Cry proteins from Bacillus thuringiensis (Bt) are major insecticidal toxins in formulated Bt sprays and are expressed in genetically engineered Bt crops for insect pest control. However, the widespread application of Bt toxins in the field imposes strong selection pressure on target insects, leading to the evolution of insect resistance to the Bt toxins. Identification and understanding of mechanisms of insect resistance to Bt toxins are an important approach for dissecting the modes of action of Bt toxins and providing knowledge necessary for the development of resistance management technologies. In this study, cabbage looper (Trichoplusia ni) strains resistant to the transgenic dual-Bt toxin WideStrike cotton plants, which express Bt toxins Cry1Ac and Cry1F, were selected from T. ni strains resistant to the Bt formulation Bt-DiPel. The WideStrike-resistant T. ni larvae were confirmed to be resistant to both Bt toxins Cry1Ac and Cry1F. From the WideStrike-resistant T. ni, the Cry1F resistance trait was further isolated to establish a T. ni strain resistant to Cry1F only. The levels of Cry1F resistance in the WideStrike-resistant and the Cry1F-resistant strains were determined, and the inheritance of the Cry1F-resistant trait in the two strains was characterized. Genetic association analysis of the Cry1F resistance trait indicated that the Cry1F resistance in T. ni isolated in this study is not shared with the Cry1Ac resistance mechanism nor is it associated with a mutation in the ABCC2 gene, as has so far been reported in Cry1F-resistant insects. IMPORTANCE Insecticidal toxins from Bacillus thuringiensis (Bt) are highly effective for insect control in agriculture. However, the widespread application of Bt toxins exerts strong selection for Bt resistance in insect populations. The continuing success of Bt biotechnology for pest control requires the identification of resistance and understanding of the mechanisms of resistance to Bt toxins. Cry1F is an important Bt toxin used in transgenic cotton, maize, and soybean varieties adopted widely for insect control. To understand the mode of action of Cry1F and mechanisms of Cry1F resistance in insects, it is important to identify Cry1F-specific resistance and the resistance mechanisms. In this study, Trichoplusia ni strains resistant to commercial "WideStrike" cotton plants that express Bt toxins Cry1Ac and Cry1F were selected, and a Cry1F-specific resistant strain was isolated. The isolation of the novel Cry1F-specific resistance in the T. ni provided an invaluable biological system to discover a Cry1F-specific novel resistance mechanism.

Foliar application of mepiquat chloride and nitrogen improves yield and fiber quality traits of cotton (Gossypium hirsutum L.).

Cotton (Gossypium hirsutum L.) is one of the most important cash crops primarily grown for fiber. It is a perennial crop with indeterminate growth pattern. Nitrogen (N) is extremely important for vegetative growth as balanced N-nutrition improves photosynthesis, resulting in better vegetative growth. Excessive N-supply results in more vegetative growth, which increases the incidence of insect pest and diseases’ infestation, pollute surface and ground water, delays maturity and produces low crop yield with poor quality. The use of plant growth regulators (PGRs) is an emerging option to control excessive vegetative growth. The PGRs help in improving plant architecture, boll retention, boll opening, yield and quality by altering growth and physiological processes such as photosynthesis, assimilate partitioning and nutrients dynamic inside the plant body. Mepiquat chloride (1,1-dimethylpiperidinum chloride) is globally used PGR for canopy development and control of excessive vegetative growth in cotton. This study investigated the effect of mepiquat chloride (MC) and N application on yield and yield components of transgenic cotton variety ‘BT-FSH-326’. Two N rates (0, 198 kg ha-1) and five MC rates (0, 30,60, 90 and 120 g ha-1) were included in the study. Results revealed that MC and N application improved boll weight, number of bolls per plant, and seed cotton and lint yields. The highest seed cotton and lint yields (3595 kg ha-1 and 1701 kg ha-1, respectively) were observed under foliar application of 198 kg ha-1 N and 120 g ha-1 MC. Fiber length, fiber strength, micronaire and uniformity were significantly improved with foliar application of MC and N. In conclusion, foliar application of MC and N could be helpful in improving yield and fiber quality of cotton.

Engineered resistance and risk assessment associated with insecticidal and weeds resistant transgenic cotton using wister rat model

Stacking multiple genes into cotton crop to cop up multiple biotic stresses such as insects and weeds is a promising tool to save crop from losses. Transgenic cotton variety, VH-289, with double Bt and cp4EPSPS genes under the control of 35S promoter was used for the expression analyses and biosafety studies. The transgenic cotton plants were screened through PCR amplification of fragments, 1.7 kb for Cry1Ac, 582 bp for Cry2A and 250 bp for cp4EPSPS; which confirmed the presence of all genes transformed in transgenic cotton. The Cry1Ac + Cry2A and cp4EPSPS proteins were quantified through ELISA in transgenic cotton plants. The Glyphosate assay performed by spraying 1900 mL per acre of glyphosate Roundup further confirmed complete survival of transgenic cotton plants as compared to the non-transgenic cotton plants and all weeds. Similarly, insect infestation data determined that almost 99% insect mortality was observed in controlled field grown transgenic cotton plants as compared to the non-transgenic control plants. Evaluation of effect of temperature and soil nutrients availability on transgene expression in cotton plants was done at two different cotton growing regions, Multan and Lahore, Pakistan and results suggested that despite of higher temperature in Multan field, an increased level of Cry and cp4EPSPS proteins was recorded due to higher soil organic matter availability compared to Lahore field. Before commercialization of any transgenic variety its biosafety study is mandatory so, a 90 days biosafety study of the transgenic cotton plants with 40% transgenic cottonseeds in standard diet showed no harmful effect on wister rat model when studied for liver function, renal function and serum electrolyte.

Enhancing the resilience of transgenic cotton for insect resistance.

The efficacy of Bt crystal proteins has been compromised due to their extensive utilization in the field. The second-generation Bt vegetative insecticidal proteins could be the best-suited alternative to combat resistance build-up due to their broad range affinity with midgut receptors of insects. The codon-optimized synthetic vegetative insecticidal proteins (Vip3Aa) gene under the control of CaMV35S promoter was transformed into a locally developed transgenic cotton variety (CKC-01) expressing cry1Ac and cry2A genes. Transformation efficiency of 1.63% was recorded. The highest Vip3Aa expression (51.98-fold) was found in MS3 transgenic cotton plant. Maximum Vip3Aa protein concentration (4.23µg/mL) was calculated in transgenic cotton plant MS3 through ELISA. The transgenic cotton plant (MS3) showed one copy number on both chromatids in the homozygous form at chromosome 8 at the telophase stage. Almost 99% mortality of H. armigera was recorded in transgenic cotton plants expressing double crystal proteins pyramided with Vip3Aa gene as contrasted to transgenic cotton plant expressing only double crystal protein with 70% mortality. The results obtained during this study suggest that the combination of Bt cry1Ac, cry2A, and Vip3Aa toxins is the best possible alternative approach to combat chewing insects.

Effect of salt stress on secondary metabolites of cotton and biological characteristics and detoxification enzyme activity of cotton spider mites

Cotton spider mites (Tetranychus cinnabarinus Boisduvals and T. truncatus Ehara) are important pest of Bt cotton. Abiotic stress, such as salt stress will not only affect the growth and development, but also cause secondary metabolism changes in cotton plants, which may further influence the occurrence of cotton spider mites on the stressed plants. The objective of the present study was to determine the relationships of salt stress with secondary metabolism and cotton spider mite population dynamics. Two transgenic cotton varieties, SCRC28 and K836, currently grown in large areas in saline-alkali land and stressed with varying concentrations of NaCl, were used. The content of gossypol and tannin, two important secondary insect-resistant substances in cotton plants, were determined in cotton leaves stressed along a NaCl gradient. The development, reproduction and detoxification enzyme activity of cotton spider mites were also studied. The results indicated that the gossypol content in SCRC28 and K836 leaves increased by 34.63% and 30.91% with 200 m mol·L−1 of added NaCl, respectively. The tannin content increased by 40.63% and 34.87%. With the increase of salt concentration, the number of mites on salt-stressed cotton decreased compared to controls. The developmental period of cotton spider mites in salt-stressed plants was significantly extended, while the reproductive rate of cotton spider mites was significantly reduced compared to controls. The development duration of the immature stages under the 200 m mol·L−1 NaCl treatments of SCRC28 and K836 increased by 12.84% and 11.94%, relative to the control, respectively. The fecundity of single female feeding on salt-stressed (200 m mol·L−1 NaCl) SCRC28 and K836 reduced by 31.96% and 36.16%, respectively. The CarE activities of cotton spider mite feeding on SCRC28 and K836 with 200 m mol·L−1 NaCl treated were 3.76 and 2.05 fold of the control, respectively; the P450 activities were 2.55 and 5.48 fold of the control, respectively. Correlation analysis indicated that the gossypol and tannin contents in cotton leaves were positively correlated with the CarE activity or P450 activity. Thus, salt stress enhanced secondary metabolism and increased accumulation of secondary metabolites such as gossypol and tannin, which ultimately inhibited the population dynamics of cotton spider mites. Cotton spider mites metabolized gossypol and tannin by increasing the activity of CarE and P450.

Transgenic Cry1Ac/CpTI cotton assessment finds no detrimental effects on the insect predator Chrysoperla sinica

The widespread commercialization of genetically modified (GM) cotton makes it important to assess the potential impact of this recombinant crop on non-target organisms. As important natural enemies of cotton field predators, green lacewing Chrysoperla sinica larvae are exposed to Bt insecticidal proteins expressed by GM cotton by feeding on herbivorous pests, and adults are directly exposed to Bt proteins by cotton pollen consumption. However, potential impacts of transgenic Bt cotton on C. sinica remain unclear. In this study, we evaluated the effects of two transgenic cotton varieties, CCRI41 and CCRI45, which express Cry1Ac (Bt toxin) and CpTI (Cowpea Trypsin Inhibitor), on C. sinica larvae and adults. After being fed with cotton aphids Aphis gossypii reared on transgenic cotton, the survival rate, developmental duration, pupation rate, and emergence rate of larvae were not adversely affected. After being fed two types of transgenic cotton pollen, the 7-day weight of adults and the preoviposition period and the cumulative oviposition of females were not significantly different from control specimen. Taken together, these results indicate that the potential risks of the two tested GM cotton varieties for the predator C. sinica are negligible. CapsuleOur study indicated that GM cotton varieties CCRI41 and CCRI45 have no adverse effects on insect predator C. sinica.

Reduced Membrane-Bound Alkaline Phosphatase Does Not Affect Binding of Vip3Aa in a Heliothis virescens Resistant Colony.

The Vip3Aa insecticidal protein from Bacillus thuringiensis (Bt) is produced by specific transgenic corn and cotton varieties for efficient control of target lepidopteran pests. The main threat to this technology is the evolution of resistance in targeted insect pests and understanding the mechanistic basis of resistance is crucial to deploy the most appropriate strategies for resistance management. In this work, we tested whether alteration of membrane receptors in the insect midgut might explain the >2000-fold Vip3Aa resistance phenotype in a laboratory-selected colony of Heliothis virescens (Vip-Sel). Binding of 125I-labeled Vip3Aa to brush border membrane vesicles (BBMV) from 3rd instar larvae from Vip-Sel was not significantly different from binding in the reference susceptible colony. Interestingly, BBMV from Vip-Sel larvae showed dramatically reduced levels of membrane-bound alkaline phosphatase (mALP) activity, which was further confirmed by a strong downregulation of the membrane-bound alkaline phosphatase 1 (HvmALP1) gene. However, the involvement of HvmALP1 as a receptor for the Vip3Aa protein was not supported by results from ligand blotting and viability assays with insect cells expressing HvmALP1.

Effect of Farm Yard Manure and Compost Application on Transgenic BT Cotton Varieties

Effect of Farm Yard Manure and Compost Application on Transgenic BT Cotton Varieties

Helicoverpa zea (Lepidoptera: Noctuidae) Preference for Plant Structures, and Their Location, Within Bt Cotton Under Different Nitrogen and Irrigation Regimes

Helicoverpa zea Boddie is a common economic pest of cotton (Gossypium hirsutum L.), including transgenic cotton varieties that express Bacillus thuringiensis (Bt). Helicoverpa zea oviposition is similar in Bt and non-Bt cotton, but behavior of H. zea larvae can be different in the presence of Bt, with neonates moving away from terminals faster in single-toxin Bt than non-Bt cotton or avoiding Bt-treated diet in the lab. We quantified H. zea oviposition and larval distribution on structures within cotton plants in small plot experiments of Cry1Ac + Cry1F cotton for 2 yr under different irrigation and nitrogen treatments. More eggs were oviposited on plants receiving nitrogen application during 2016 and on leaves in the top section of irrigated plants during 2017, but other treatment effects on eggs or larvae were minimal. Helicoverpa zea eggs were most common on leaves in the top third of plants at position zero and middle section of cotton plants throughout the season, but some oviposition occurred on fruiting structures as well. First and second instars were more common on squares in the top section of plants during 2016 and bolls in the middle and lower sections during 2017 due to oviposition lower in the canopy during 2017. During both years, third through fifth instars were more common on bolls in the middle and lower section of plants closer to the main stem. These findings have resistance management implications as extended larval feeding on bolls could optimize nutrition, decrease Bt susceptibility, and potentially influence behavioral resistance.

Screening of salt tolerant transgenic and non-transgenic cotton varieties under various levels of NaCl induced salinity stress

Screening of salt tolerant transgenic and non-transgenic cotton varieties under various levels of NaCl induced salinity stress

First transgenic trait for control of plant bugs and thrips in cotton.

BACKGROUNDPlant bugs (Lygus spp.) and thrips (Thrips spp.) are two of the most economically important insect pest groups impacting cotton production in the USA today, but are not controlled by current transgenic cotton varieties. Thus, seed or foliar‐applied chemical insecticides are typically required to protect cotton from these pest groups. Currently, these pests are resistant to several insecticides, resulting in fewer options for economically viable management. Previous publications documented the efficacy of transgenic cotton event MON 88702 against plant bugs and thrips in limited laboratory and field studies. Here, we report results from multi‐location and multi‐year field studies demonstrating efficacy provided by MON 88702 against various levels of these pests.RESULTSMON 88702 provided a significant reduction in numbers of Lygus nymphs and subsequent yield advantage. MON 88702 also had fewer thrips and minimal injury. The level of control demonstrated by this transgenic trait was significantly better compared with its non‐transgenic near‐isoline, DP393, receiving insecticides at current commercial rates.CONCLUSIONThe level of efficacy demonstrated here suggests that MON 88702, when incorporated into existing IPM programs, could become a valuable additional tool for management of Lygus and thrips in cotton agroecosystems experiencing challenges of resistance to existing chemical control strategies. © 2018 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Efficiency of cotton bollworm (Helicoverpa armigera H\xfcbner) control of different Bt cotton varieties in North China

BackgroundThe cotton bollworm (Helicoverpa armigera) is one of cotton’s most destructive insect pests in terms of yield and quality. Since 1997, China has grown commercially available transgenic Bacillus thuringiensis (Bt) cotton. We aimed to investigate the variation in resistance of transgenic Bt cotton varieties to cotton bollworm in North China.MethodsPopulations of cotton bollworm were monitored from 2008 to 2015 in environments where Bt cotton was planted adjacent to other non-Bt crops. The study included 197 Bt cotton varieties planted in 42 counties/locations in three provinces (Hebei, Shandong and Henan) of North China, which were evaluated through field investigations, bioassays, and enzyme-linked immunosorbent assays (ELISA).ResultsThe average number of cotton bollworms never exceeded the action threshold (10 larvae per 100 cotton plants), however, their number reached 19.55 per 100 cotton plants in 2011. The ratios of damaged plants to total Bt cotton stem-tips, buds, and bolls was low except in 2010, when the ratios reached 1.82%, 2.09%, and 10.63%, respectively. The results of bioassay showed that the corrected mortality were higher at the second generation cotton bollworm stage than the third and fourth germination stages. Totally, Bt protein content declined sharply at the seedling stage from 2008 to 2015.ConclusionsThis study indicated that almost all Bt cotton varieties were capable to effectively control the populations of cotton bollworm in North China.

Seasonal population dynamics of dusky cotton bug (Oxycarenus spp.) in transgenic cotton varieties under field conditions.

Dusky cotton bug (Oxycarenus spp.) has become a major insect pest for cotton crop in Pakistan. Transgenic cotton varieties provided resistance to a variety of insects pests. But, these are not safe for this emerging potential threat. In present study, nine transgenic cotton varieties (IUB-222, MNH-886, FH-142, CIM-599, A-555, CIM-602, NIAB-777, MNH-786 and Bt-666) were assessed for seasonal population dynamics of dusky cotton bug (DCB) under field conditions. All transgenic varieties showed a differential DCB population over the months and no transgenic variety was free from DCB population throughout the crop duration. DCB population appeared during 3rd week of July and crossed the economic threshold level (10–15 nymph/ adults or both per plant) during August. A substantial increase in DCB population was noted during September-November with its peak population during October, 2014. Among all varieties, three varieties (CIM-599, CIM-602 & IUB-222) showed a significantly lower mean population per plant (37.76, 37.87, 43.84) and two varieties (FH-142, MNH-886) gave highest population (44.71, 46.81), respectively. Correlation matrix revealed that low temperature and high humidity were promoting the DCB population. Cluster analysis revealed interesting findings that IUB-222 with least population fall in a cluster where other two varieties (FH-142 & MNH-886) possessed highest population. Moreover, two varieties (CIM-599 & CIM-602) with least population fall in second cluster regarding DCB population. These findings would be helpful for the farmers to select the varieties that showed relatively higher resistance towards DCB population and to adopt proper management strategies keeping in view the trend of DCB population during the crop season.

The Effect of the Different Transgenic BT Cotton Technology on the Fiber Quality

Transgenic crops that contain Cry genes from B. thuringiensis (Bt) were commercialized in many countries and widely adopted by farmers over the last 17 years. The cultivation of transgenic crops expressing B. thuringiensis (Bt) toxins to control insect pests provides both economical and environmental benefits from reductions in chemical insecticide use, effective control of pests and minimal impact on non-target organisms. The objective of this research was to know the effect of different transgenic Bt cotton on the fiber quality of different Bt cotton varieties. Three transgenic Bt cotton varieties CCR141, CCRI79 and Bollgard II were planted in the field of Institute of Cotton Research Chinese Academy of Agricultural Sciences during 2012 and 2013. Randomly 50 bolls lint sample were collected from top, middle and bottom of the cotton plants. The fiber obtained from the boll samples was used to measure the cotton fiber staple length (mm), staple elongation (%), staple micronaire value, staple strength (cN/tex) and staple uniformity (%) by using HVI equipment at Supervision, Inspection and Testing Center of cotton Quality, China. The result shows that lint quality characters of transgenic cotton varieties were not significantly affected compared with conventional non Bt variety during 2012 and 2013 but fiber strength is significantly affected during 2013. In conclusion there was no effect of transgenic Bt cotton on the fiber quality of cotton during 2012 and 2013.