scholarly journals Bacterial Microbiota of Field-Collected Helicoverpa zea (Lepidoptera: Noctuidae) from Transgenic Bt and Non-Bt Cotton

2021 ◽  
Vol 9 (4) ◽  
pp. 878
Author(s):  
Jean M. Deguenon ◽  
Anirudh Dhammi ◽  
Loganathan Ponnusamy ◽  
Nicholas V. Travanty ◽  
Grayson Cave ◽  
...  

The bollworm, Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae), is an important agricultural pest in U.S. cotton and is managed using transgenic hybrids that produce insecticidal proteins from the bacterium, Bacillus thuringiensis (Bt). The reduced efficacy against H. zea caterpillars of Bt plants expressing Cry toxins is increasing in the field. In a first step towards understanding Bt cotton–bollworm–microbiota interactions, we investigated the internal bacterial microbiota of second–third stadium H. zea collected in the field from non-Bt versus Bt (WideStrike) cotton in close proximity (in North Carolina, USA). The bacterial populations were analyzed using culture-dependent and -independent molecular approaches. We found that WideStrike samples had a higher bacterial density and diversity per larva than insects collected from non-Bt cotton over two field seasons: 8.42 ± 0.23 and 5.36 ± 0.75 (log10 colony forming units per insect) for WideStrike compared to 6.82 ± 0.20 and 4.30 ± 0.56 for non-Bt cotton for seasons 1 and 2, respectively. Fifteen phyla, 103 families, and 229 genera were identified after performing Illumina sequencing of the 16S rRNA. At the family level, Enterobacteriaceae and Enterococcaceae were the most abundant taxa. The Enterococcaceae family was comprised mostly of Enterococcus species (E. casseliflavus and another Enterococcus sp.). Members of the Enterococcus genus can acidify their environment and can potentially reduce the alkaline activation of some Bt toxins. These findings argue for more research to better understand the role of cotton–bollworm–bacteria interactions and the impact on Bt toxin caterpillar susceptibility.

2020 ◽  
Author(s):  
Wenhui Wang ◽  
Feng Xu ◽  
Yunxin Huang ◽  
Hongqiang Feng ◽  
Peng Wan

Abstract Background Transgenic maize expressing toxins derived from the bacterium Bacillus thuringiensis (Bt) may be commercially planted in northern China where Bt cotton has been planted for more than two decades. While Bt maize brings additional benefits for insect control, it complicates the resistance management of cotton bollworm (CBW), Helicoverpa armigera (Lepidoptera, Noctuidae), a common target of Bt cotton and Bt maize. Results We used a two-locus population genetic model to assess the risk of resistance in CBW when Bt cotton and Bt maize are planted concurrently. Results of model simulations showed that planting Bt maize together with Bt cotton significantly increases the risk of resistance if Bt cotton and Bt maize share a similar Bt toxin. The risk of resistance is higher in the case of one-toxin Bt maize than in the case of two-toxin Bt maize. Parameters associated with the preexisting resistance in CBW all could impact on the risk of resistance but with different extents. Among them, the most notable ones are the dominance of resistance and fitness cost, which can dramatically affect the risk of resistance, especially when the proportion of natural refuges is reduced. Conclusions We concluded that the preexisting resistance in CBW to Bt cotton can significantly increase the risk of resistance when Bt maize and Bt cotton are planted concurrently and that using two-toxin Bt cotton and maize instead of one-toxin ones are needed in order to reduce the risk of resistance.


2016 ◽  
Vol 107 (2) ◽  
pp. 188-199 ◽  
Author(s):  
G.H. Baker ◽  
C.R. Tann

AbstractThe cotton bollworm, Helicoverpa armigera, is a major pest of many agricultural crops in several countries, including Australia. Transgenic cotton, expressing a single Bt toxin, was first used in the 1990s to control H. armigera and other lepidopteran pests. Landscape scale or greater pest suppression has been reported in some countries using this technology. However, a long-term, broad-scale pheromone trapping program for H. armigera in a mixed cropping region in eastern Australia caught more moths during the deployment of single Bt toxin cotton (Ingard®) (1996–2004) than in previous years. This response can be attributed, at least in part, to (1) a precautionary cap (30% of total cotton grown, by area) being applied to Ingard® to restrict the development of Bt resistance in the pest, and (2) during the Ingard® era, cotton production greatly increased (as did that of another host plant, sorghum) and H. armigera (in particular the 3rd and older generations) responded in concert with this increase in host plant availability. However, with the replacement of Ingard® with Bollgard II® cotton (containing two different Bt toxins) in 2005, and recovery of the cotton industry from prevailing drought, H. armigera failed to track increased host-plant supply and moth numbers decreased. Greater toxicity of the two gene product, introduction of no cap on Bt cotton proportion, and an increase in natural enemy abundance are suggested as the most likely mechanisms responsible for the suppression observed.


2019 ◽  
Vol 112 (4) ◽  
pp. 1741-1751
Author(s):  
Lewis R Braswell ◽  
Dominic D Reisig ◽  
Clyde E Sorenson ◽  
Guy D Collins

Abstract 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.


2015 ◽  
Vol 154 (1) ◽  
pp. 109-117 ◽  
Author(s):  
H. M. N. CHEEMA ◽  
A. A. KHAN ◽  
M. I. KHAN ◽  
U. ASLAM ◽  
I. A. RANA ◽  
...  

SUMMARYGenetically modified (GM) plants expressing Bt toxin provide protection against lepidopteran pests. The only GM crop in Pakistan is Bt cotton, which was illegally imported and adopted rapidly by cotton producers. Farmers gained access to the seed of many unapproved Bt genotypes before the matter was picked up and formal approval granted by the relevant governmental agencies. The present study was conducted to evaluate the samples of Bt cotton, collected from farmers and seed dealer, for transgene integration and expression. Seeds of 52 cotton genotypes, labelled as Bt, were collected from various farmers and seed dealers. An immunoblot strip test was carried out, which showed that only 0·86 of the samples collected were synthesizing Cry1Ac toxin. According to multiplexed polymerase chain reaction (PCR) results, 0·86 of the genotypes tested were positive for the Mon531 event (an ‘event’ is a specific genetic modification in a specific species) and 0·14 were negative for any transgene. Transcript analysis of transgenes in positive genotypes by real-time Rt-PCR confirmed the synthesis of mRNA in all genotypes but with significant variation. The concentration of Bt toxin revealed by enzyme linked immunosorbent assay (ELISA) showed that only 0·02 genotypes had the reported optimum level. The real-time PCR and ELISA results further confirmed the attenuation of transgene expression at transcriptional and translational level by various internal and external factors. The same type of event was found in all genotypes, with significant variation in toxin level, revealing the impact of genetic background on transgene expression. The findings support the recommendation to improve the existing quality criteria for transgenic cotton variety approval and certification in Pakistan, with the inclusion of toxin concentration in the list of parameters to be considered.


2021 ◽  
Author(s):  
Wenhui Wang ◽  
Feng Xu ◽  
Yunxin Huang ◽  
Hongqiang Feng ◽  
Peng Wan

Abstract BackgroundTransgenic maize expressing toxins derived from the bacterium Bacillus thuringiensis (Bt) may be commercially planted in northern China where Bt cotton has been planted for more than two decades. While Bt maize brings additional benefits for insect control, it complicates the resistance management of cotton bollworm (CBW), Helicoverpa armigera (Lepidoptera, Noctuidae), a common target of Bt cotton and Bt maize.ResultsWe developed population genetic models to assess the risk of resistance in CBW when Bt cotton and Bt maize are planted concurrently. Model simulations showed that when natural refuges are absent, the time to resistance (TTR) is less than 10 generations in the case of one-toxin Bt cotton and one-toxin Bt maize, but is more than 30 generations in the case of two-toxin Bt cotton and two-toxin Bt maize. The differences in the TTR between the two cases become greater as the proportion of natural refuge increases. Among the parameters we investigated, the fitness cost has a relatively smaller effect on the TTR, while the dominance of resistance and the proportion of natural refuge have a much greater effect.ConclusionsWe concluded that planting the first generation Bt cotton with Bt maize could significantly increase the risk of CBW resistance to Bt toxins as compared to planting a pyramid two-toxin Bt cotton. The strategies for reducing the risk of CBW resistance include replacing the one-toxin Bt cotton with a pyramid two-toxin Bt cotton, adopting a pyramid two-toxin Bt maize, and maintaining a sufficient proportion of natural refuges.


1996 ◽  
Vol 31 (2) ◽  
pp. 209-217
Author(s):  
C. E. Rogers ◽  
O. G. Marti ◽  
L. D. Chandler ◽  
A. M. Simmons

The fall armyworm, Spodoptera frugiperda (J. E. Smith), is a perennial immigrant pest of several crops in south Georgia. Moths of S. frugiperda commonly are infested by an ectoparasitic nematode, Noctuidonema guyanense Remillet and Silvain in the Southeast. The seasonal chronology and natural association of these species are reported for Tift Co. from 1988 to 1994. Seasonal influxes of non-infested moths usually arrive in late April and dissipate in early November. Seasonal influxes of infested male moths follow the initial immigrants by 4 to 6 wks and disappear in the fall from 1 to 2 mos earlier than the general moth populations. Feral male moths that are moderately worn and infested by N. guyanense weigh less than moderately worn, non-infested males. Noctuidonema guyanense infests moths of several species of noctuids, but it has not been found on the cotton bollworm/corn earworm [Helicoverpa zea (Boddie)], tobacco budworm [Heliothis virescens (Fab.)], or beet armyworm [S. exigua (Hubner)].


2000 ◽  
Vol 35 (4) ◽  
pp. 360-372 ◽  
Author(s):  
Muhammad Ashfaq ◽  
S. Y. Young ◽  
R. W. McNew

The effects of transgenic Bacillus thuringiensis (Bt)-cotton on three instars of Spodoptera exigua (Hübner) and Helicoverpa zea (Boddie) were studied. First, third and fifth instars were fed field-collected Bt-cotton leaves for 1, 2, 3, 4 and 7 d or until pupation, and then transferred to artificial diet. Larval mortality at pupation, length of larval and pupal periods, pupal weights and survival time from hatch to adult were recorded for regular and Bt-cotton. Larval mortality at pupation in S. exigua fed Bt-cotton was low for all instars exposed and feeding periods on Bt-cotton. The mortality in H. zea was high for first and third instars and significantly increased with the increase in feeding period on Bt-cotton (P < 0.05). The length of larval period increased in both species when first and third instars but not fifth instars were fed Bt-cotton. In H. zea, the larval period increased when larvae were on Bt-cotton leaves for only 2 d. Pupal weight was reduced with an increase in feeding time on Bt-cotton in all three instars in both species. An increase in length of feeding time on Bt-cotton reduced survival to adults in both species on Bt-cotton in first and third instars but not in fifth instars. Survival to adults was much lower in H. zea than S. exigua for all instars exposed and feeding periods on Bt-cotton. These results demonstrate the large differences in effectiveness of Bt-cotton against lepidopteran cotton pests, as well as the adverse effects on larvae developing on Bt-cotton.


2009 ◽  
Vol 35 (7) ◽  
pp. 785-795 ◽  
Author(s):  
Konasale J. Anilkumar ◽  
Sakuntala Sivasupramaniam ◽  
Graham Head ◽  
Robert Orth ◽  
Edzard Van Santen ◽  
...  

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