A Comprehensive Assessment of the Effects of Bt Cotton on Coleomegilla maculata Demonstrates No Detrimental Effects by Cry1Ac and Cry2Ab (original) (raw)
Related papers
Journal of Economic Entomology, 2008
Cry1Ac protoxin (the active insecticidal toxin in both Bollgard and Bollgard II cotton [Gossypium hirsutum L.]), and Cry2Ab2 toxin (the second insecticidal toxin in Bollgard II cotton) were bioassayed against Þve of the primary lepidopteran pests of cotton by using diet incorporation. Cry1Ac was the most toxic to Heliothis virescens (F.) and Pectinophora gossypiella (Saunders), demonstrated good activity against Helicoverpa zea (Boddie), and had negligible toxicity against Spodoptera exigua (Hü bner) and Spodoptera frugiperda (J. E. Smith). Cry2Ab2 was the most toxic to P. gossypiella and least toxic to S. frugiperda. Cry2Ab2 was more toxic to S. exigua and S. frugiperda than Cry1Ac. Of the three insect species most sensitive to both Bacillus thuringiensis (Bt) proteins (including H. zea), P. gossypiella was only three-fold less sensitive to Cry2Ab2 than Cry1Ac, whereas H. virescens was 40-fold less sensitive to Cry2Ab2 compared with Cry1Ac. Cotton plants expressing Cry1Ac only and both Cry1Ac and Cry2Ab2 proteins were characterized for toxicity against H. zea and S. frugiperda larvae in the laboratory and H. zea larvae in an environmental chamber. In no-choice assays on excised squares from plants of different ages, second instar H. zea larvae were controlled by Cry1Ac/Cry2Ab2 cotton with mortality levels of 90% and greater at 5 d compared with 30 Ð 80% mortality for Cry1Ac-only cotton, depending on plant age. Similarly, feeding on leaf discs from Cry1Ac/Cry2Ab2 cotton resulted in mortality of second instars of S. frugiperda ranging from 69 to 93%, whereas exposure to Cry1Ac-only cotton yielded 20 Ð 69% mortality, depending on plant age. When cotton blooms were infested in situ in an environmental chamber with neonate H. zea larvae previously fed on synthetic diet for 0, 24, or 48 h, 7-d ßower abortion levels for Cry1Ac-only cotton were 15, 41, and 63%, respectively, whereas for Cry1Ac/Cry2Ab2 cotton, ßower abortion levels were 0, 0, and 5%, respectively. Cry1Ac and Cry2Ab2 concentrations were measured within various cotton tissues of Cry1Ac-only and Cry1Ac/Cry2Ab2 plants, respectively, by using enzyme-linked immunosorbent assay. Terminal leaves signiÞcantly expressed the highest, and large leaves, calyx, and bracts expressed signiÞcantly the lowest concentrations of Cry1Ac, respectively. Ovules expressed signiÞcantly the highest, and terminal leaves, large leaves, bracts, and calyx expressed signiÞcantly (P Ͻ 0.05) the lowest concentrations of Cry2Ab2. These results help explain the observed differences between Bollgard and Bollgard II mortality against the primary lepidopteran cotton pests, and they may lead to improved scouting and resistance management practices, and to more effective control of these pests with Bt transgenic crops in the future.
Bioengineered, 2015
Insecticidal Cry proteins from Bacillus thuringiensis (Bt) have been exploited in the development of genetically modified (GM) crops for pest control. However, several pests are still difficult to control such as the coleopteran boll weevil Anthonomus grandis. By applying in vitro molecular evolution to the cry8Ka1 gene sequence, variants were generated with improved activity against A. grandis. Among them, Cry8Ka5 mutant protein showed coleoptericidal activity three-fold higher (LC50 2.83 μg/mL) than that of the original protein (Cry8Ka1). Cry8Ka5 has been used in breeding programs in order to obtain coleopteran-resistant cotton plants. Nevertheless, there is some concern in relation to the food safety of transgenic crops, especially to the heterologously expressed proteins. In this context, our research group has performed risk assessment studies on Cry8Ka5, using the tests recommended by Codex as well as tests that we proposed as alternative and/or complementary approaches. Our r...
Journal of Economic Entomology, 2000
In Australia, transgenic cotton plants expressing the cry1Ac gene from Bacillus thuringiensis Berliner variety kurstaki are less toxic to Þrst-instar Helicoverpa armigera (Hü bner) after the plant is producing fruit. We developed two bioassay methods (leaf mush, leaf disk) to test if the physiological state of the plants explained changes in toxicity and a third method (diet incorporation) was developed to quantify the toxicity of Bt leaves when mixed in chickpea diet. Cry1Ac protein was less toxic to H. armigera larvae when the protein was mixed with leaves from fruiting versus presquare conventional cotton. Differences in LC 50 varied from 2.4-to 726-fold, depending on the source of toxin and conventional plant material. These results suggest that plant-toxin interactions in fruiting cotton are reducing the toxicity of the Cry1Ac protein. The possible role of tannins in these changes is discussed.
Bt cotton : A boon against insect resistance
2019
The cultivation of transgenic cotton is increased in a large scale since from its introduction globally. Bacillus thuringiensis is produced crystalline proteins, these proteins were used in transgenic cotton to control insect pest. Resistance in insects is a major problem in transgenic cotton growing regions in all over the world especially, pink boll worm developed resistance in all major cotton regions in India. It was noticed in our studies that the expression levels of Cry1Ac in different plant parts such as upper leaves, lower leaves, sepals and boll bracts was increased while increasing refuge percentage. Planting refuge with alternatively with Bt cotton also increase the Cry1Ac expression levels compare with border refuge. An optimized unique combination of refuge crop viz., 75% Bt with 25% nBt showed higher expression level of Cry1Ac and highest yield was also achieved. This combination is useful to counter insect resistance and the staking of two toxin Cry proteins in same ...
Transgenic Research, 2008
A number of cotton varieties have been genetically transformed with genes from Bacillus thuringiensis (Bt) to continuously produce Bt endotoxins, offering whole plant and season-long protection against many lepidopteran larvae. Constant whole-plant toxin expression creates a significant opportunity for non-target herbivores to acquire and bio-accumulate the toxin for higher trophic levels. In the present study we investigated movement of Cry1Ac toxin from the transgenic cotton plant through specific predator-prey pairings, using omnivorous predators with common cotton pests as prey: (1) the beet armyworm, Spodoptera exigua (Lepidoptera: Noctuidae), with the predator Podisus maculiventris (Heteroptera: Pentatomidae); (2) the two-spotted spider mite, Tetranychus urticae (Acarina: Tetranychidae), with the predatory big-eyed bug Geocoris punctipes (Heteroptera: Geocoridae) and (3) with the predatory damsel bug Nabis roseipennis (Heteropera: Nabidae); and (4) the thrips Frankliniella occidentalis (Thysanoptera: Thripidae) with the predatory pirate bug Orius insidiosus (Heteroptera: Anthocoridae). We quantified Cry1Ac toxin in the cotton plants, and in the pests and predators, and the effects of continuous feeding on S. exigua larvae fed either Bt or non-Bt cotton on life history traits of P. maculiventris. All three herbivores were able to convey Cry1Ac toxin to their respective predators. Among the herbivores, T. urticae exhibited 16.8 times more toxin in their bodies than that expressed in Bt-cotton plant, followed by S. exigua (1.05 times), and F. occidentalis immatures and adults (0.63 and 0.73 times, respectively). Of the toxin in the respective herbivorous prey, 4, 40, 17 and 14% of that amount was measured in the predators G. punctipes, P. maculiventris, O. insidiosus, and N. roseipennis, respectively. The predator P. maculiventris exhibited similar life history characteristics (developmental time, survival, longevity, and fecundity) regardless of the prey’s food source. Thus, Cry1Ac toxin is conveyed through non-target herbivores to natural enemies at different levels depending on the herbivore species, but continuous lifetime contact with the toxin by the predator P. maculiventris through its prey had no effect on the predator’s life history. The results found here, supplemented with others already published, suggest that feeding on Cry1Ac contaminated non-target herbivores does not harm predatory heteropterans and, therefore, cultivation of Bt cotton may provide an opportunity for conservation of these predators in cotton ecosystems by reducing insecticide use.
Biological Control, 2006
The continuous expression of the Bt ( D Bacillus thuringiensis) toxin in plants during the growing season may bring Bt toxin into contact with the omnivorous big-eyed bug Geocoris punctipes (Say) (Hemiptera: Geocoridae), an important predator in cotton Welds, through prey fed Bt-cotton or through plant feeding. Therefore, an experiment was set up during two seasons (2003 and 2004) in the Weld to assess host plant-and prey-mediated eVects on development and reproduction of the predator. We used a combination of Bt and non-Bt cotton plants, and of prey, with one treatment conveying Bt Cry1Ac toxin to the upper trophic level [Spodoptera exigua (Hübner) larvae (BAW)] and the other prey item free of toxin [Helicoverpa zea (Boddie) eggs (CEW)]. This design allowed us to diVerentiate direct and indirect eVects of the toxin in the host plant from eVects attributable to prey quality under Weld conditions. The experiment began with newly hatched big-eyed bug nymphs and ending when the last female died. The combination of prey and Bt-cotton plants did not exert interactive eVects on development and reproduction of the omnivorous predator. The prey eVect was independent of either host plant type. Nymphs fed BAW larvae developed slower and produced smaller adults with no diVerence between cotton genotypes. Reproductive output and longevity were similar between cottons for both prey types, and were consistently lower for predators fed BAW larvae. Cry1Ac was detected in Bt-cotton and in BAW larvae fed Bt-cotton and oVered to the predators, but not in the predators' bodies. The results do not indicate any lethal or sublethal eVect of transgenic Bt-cotton or of Cry1Ac conveyed through prey on development and reproduction of G. punctipes in our Weld experiments.
Journal of economic …, 2001
We evaluated the effects of Bacillus thuringiensis (Bt) toxin Cry1Ac on survival and development of a susceptible strain and laboratory-selected resistant strains of pink bollworm, Pectinophora gossypiella (Saunders). For susceptible and resistant strains tested on artiÞcial diet, increases in Cry1Ac concentration reduced developmental rate and pupal weight. In greenhouse tests, survival of resistant larvae on transgenic cotton that produces Cry1Ac (Bt cotton) was 46% relative to their survival on non-Bt cotton. In contrast, Bt cotton killed all susceptible larvae tested. F 1 hybrid progeny of resistant and susceptible adults did not survive on Bt cotton, which indicates recessive inheritance of resistance. Compared with resistant or susceptible larvae reared on non-Bt cotton, resistant larvae reared on Bt cotton had lower survival and slower development, and achieved lower pupal weight and fecundity. Recessive resistance to Bt cotton is consistent with one of the basic assumptions of the refuge strategy for delaying resistance to Bt cotton. Whereas slower development of resistant insects on Bt cotton could increase the probability of mating between resistant adults and accelerate resistance, negative effects of Bt cotton on the survival and development of resistant larvae could delay evolution of resistance.
Crop Protection, 2017
Fall armyworm, Spodoptera frugiperda (J.E. Smith), is a major target species of Bt maize and Bt cotton in the United States. Field resistance to Cry1F maize in S. frugiperda has occurred in Puerto Rico, Brazil, and the southeast region of the United States. There is a great concern that the Cry1F-maize resistant S. frugiperda may move to the cotton fields and cause control problems to Bt cotton where both crops are planted. In this study, larval mortality and growth inhibition of Cry1F maize-susceptible (SS),-heterozygous (RS), and-resistant (RR) genotypes of S. frugiperda were evaluated using diet-incorporated bioassays with six Bt proteins that have been used in commercialized and future Bt cotton plants: Cry1F, Cry1Ab, Cry1Ac, Cry2Ab2, Cry2Ae, and Vip3A. Compared to the mortality data, the measuring of growth inhibition was more sensitive in determining Bt susceptibility of the insect to all six Bt proteins. Overall, RS had a similar performance as SS for the six Bt proteins with a resistance ratio of < 5.5-fold. The resistance ratio of RR calculated based on larval growth inhibition was 930-fold for Cry1F, 50.5fold for Cry1Ab, and >172-fold for Cry1Ac. In contrast, all three insect genotypes were susceptible to Cry2Ab2, Cry2Ae, or Vip3A. The results showed that the Cry1F-maize resistant S. frugiperda was cross-resistant to Cry1Ab or Cry1Ac, but not cross-resistant to Cry2Ab2, Cry2Ae, or Vip3A. The strong cross-resistance among Cry1 proteins suggest that it is necessary to plant pyramided cotton traits that contain at least two active Bt genes for Cry1F-resistant S. frugiperda to ensure the continued success of the Bt cotton technology, especially in the areas where Bt resistance has already occurred.
Advance generations of different transgenic lines of locally approved cotton cultivar CIM-482 expressing two insecticidal genes (Cry1Ac and Cry2A) were confirmed for the integration and expression of insectidal genes, evaluated for the resistance against cotton boll worms especially american boll worm (Heliothis armerigera) under field condition for three consecutive years. Homozygous lines showing high insect resistance, morphological and agronomic characteristics were selected, risk assessment studies of these transgenic lines were also undertaken. Laboratory biotoxicity assays were performed to calculate the mortality %age of Heliothis larvae as a result of expression of insecticidal genes. Most of the transgenic lines showed up to 70-100% resistance against targeted insect pests. After artificial infestation of targeted insects, transgenic lines showed significant resistance levels. Data were recorded in terms of boll damage percentage. Morphological and yield data analysis were recorded. All the characters were stably inherited in advance generations. Experiments conducted to evaluated potential risk of transgenic lines on non target insects and soil organisms showed that these lines have no significant effect on non target insects (insects belonging to orders other than Lepidoptera). No any evidence of transgene flow was found from crop to soil organisms.
International Journal of Agriculture and Biology
Current study focused on expression profiling of locally bred Bt-cotton varieties through ELISA and were tested for their efficacy against survival of Helicoverpa armigera in control environment. The population dynamics of five sucking arthropods; whitefly, jassid, aphid, thrips and mites, along the growing season was also monitored and correlated with different meteorological factors. Expression levels of insecticidal protein Cry1Ab/c were found to vary significantly (P<0.05) among varieties and across different sampling dates. The highest mean expression was recorded in GN-31 and Sitara-008 and the lowest in FH-113 and MG-6 while across sampling dates the highest mean expression was recorded at 30 days after emergence (DAE) which decreased along the season with lowest mean at 120 DAE. A critical expression level of Cry1Ab/c in leaves was found at 770 ± 25 ngg-1, for 95% control of the target insect pests. Sucking pest population was found to be variable among both the cultivars...