Effects of Soil Salinity on the Expression of Bt Toxin (Cry1Ac) and the Control Efficiency of Helicoverpa armigera in Field-Grown Transgenic Bt Cotton

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.

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The influence of pesticide applications on Helicoverpa armigera Hübner and sucking pests in transgenic Bt cotton and non-transgenic cotton in China

Crop Protection ◽

10.1016/j.cropro.2004.08.006 ◽

2005 ◽

Vol 24 (4) ◽

pp. 319-324 ◽

Cited By ~ 34

Author(s):

Xingyuan Men ◽

Feng Ge ◽

Clive A. Edwards ◽

Erdal N. Yardim

Keyword(s):

Helicoverpa Armigera ◽

Transgenic Cotton ◽

Bt Cotton ◽

Transgenic Bt Cotton ◽

Helicoverpa Armígera ◽

Helicoverpa Armigera Hubner

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Effects of transgenic Bt cotton on overwintering characteristics and survival of Helicoverpa armigera

Journal of Insect Physiology ◽

10.1016/j.jinsphys.2010.10.007 ◽

2011 ◽

Vol 57 (1) ◽

pp. 153-160 ◽

Cited By ~ 19

Author(s):

Fang Ouyang ◽

Zhudong Liu ◽

Jin Yin ◽

Jianwei Su ◽

Chenzhu Wang ◽

...

Keyword(s):

Helicoverpa Armigera ◽

Bt Cotton ◽

Transgenic Bt Cotton ◽

Helicoverpa Armígera

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Oviposition site selection and survival of susceptible and resistant larvae of Helicoverpa armigera (Lepidoptera: Noctuidae) on Bt and non-Bt cotton

Bulletin of Entomological Research ◽

10.1017/s0007485316000328 ◽

2016 ◽

Vol 106 (6) ◽

pp. 710-717 ◽

Cited By ~ 11

Author(s):

T.T.A. Luong ◽

S.J. Downes ◽

B. Cribb ◽

L.E. Perkins ◽

M.P. Zalucki

Keyword(s):

Helicoverpa Armigera ◽

Site Selection ◽

Oviposition Preference ◽

Resistance Management ◽

Oviposition Site ◽

Bt Cotton ◽

Oviposition Site Selection ◽

Bt Toxin ◽

Cotton Plants ◽

Helicoverpa Armígera

AbstractIn Australia Bt cotton has been planted since 1996, and has greatly improved the control of its key target Helicoverpa armigera (Hübner). There is no strong evidence that genetically modified cotton has been selected for significant physiological resistance to Bt toxin in field populations. There are many possible explanations for the lack of apparent selection that range from high compliance with the resistance management strategy for this technology to a lack of behavioral preference in key traits such as oviposition that could favor survival. To date most experiments that test oviposition of H. armigera on Bt cotton vs. conventional cotton have been done with susceptible moths. We determine the oviposition preference of a field isolated Bt resistant line of H. armigera and a susceptible counterpart when given a choice of non-Bt cotton and Bt-cotton with the same genetic background, and test whether there is any relationship between oviposition site selection (different plant structures) and the survival of the first instar larvae. Within cotton plants, our experiments consistently showed that both resistant and susceptible moths did not choose plants or plant parts that were less toxic in terms of Bt toxin on which to lay eggs. There was one exception in that susceptible moths were more likely to lay eggs on squares of Bt cotton plants than squares of non-Bt cotton. As expected, the mortality of susceptible H. armigera neonates was significantly higher on structures of Bt cotton plants than on those structures of conventional cotton, and survival was greater on flowers than on other structures of Bt cotton. This confirms opportunities for selection for resistance, and demonstrates no advantage in this respect to carrying resistance genes that might overcome the Bt toxins.

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Mutated Cadherin Alleles from a Field Population of Helicoverpa armigera Confer Resistance to Bacillus thuringiensis Toxin Cry1Ac

Applied and Environmental Microbiology ◽

10.1128/aem.01703-07 ◽

2007 ◽

Vol 73 (21) ◽

pp. 6939-6944 ◽

Cited By ~ 68

Author(s):

Yajun Yang ◽

Haiyan Chen ◽

Yidong Wu ◽

Yihua Yang ◽

Shuwen Wu

Keyword(s):

Bacillus Thuringiensis ◽

Helicoverpa Armigera ◽

Yellow River ◽

Insect Pest ◽

Genetically Engineered ◽

Field Population ◽

Bt Cotton ◽

Transgenic Bt Cotton ◽

Helicoverpa Armígera ◽

First Time

ABSTRACT The cotton bollworm Helicoverpa armigera is the major insect pest targeted by cotton genetically engineered to produce the Bacillus thuringiensis toxin (transgenic Bt cotton) in the Old World. The evolution of this pest's resistance to B. thuringiensis toxins is the main threat to the long-term effectiveness of transgenic Bt cotton. A deletion mutation allele (r 1 ) of a cadherin gene (Ha_BtR) was previously identified as genetically linked with Cry1Ac resistance in a laboratory-selected strain of H. armigera. Using a biphasic screen strategy, we successfully trapped two new cadherin alleles (r 2 and r 3 ) associated with Cry1Ac resistance from a field population of H. armigera collected from the Yellow River cotton area of China in 2005. The r 2 and r 3 alleles, respectively, were created by inserting the long terminal repeat of a retrotransposon (designated HaRT1) and the intact HaRT1 retrotransposon at the same position in exon 8 of Ha_BtR, which results in a truncated cadherin containing only two ectodomain repeats in the N terminus of Ha_BtR. This is the first time that the B. thuringiensis resistance alleles of a target insect of Bt crops have been successfully detected in the open field. This study also demonstrated that bollworm larvae carrying two resistance alleles can complete development on Bt cotton. The cadherin locus should be an important target for intensive DNA-based screening of field populations of H. armigera.

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Plant-Toxin Interactions in Transgenic Bt Cotton and their Effect on Mortality of Helicoverpa armigera (Lepidoptera: Noctuidae)

Journal of Economic Entomology ◽

10.1603/0022-0493-93.4.1293 ◽

2000 ◽

Vol 93 (4) ◽

pp. 1293-1299 ◽

Cited By ~ 55

Author(s):

K. M. Olsen ◽

J. C. Daly

Keyword(s):

Helicoverpa Armigera ◽

Bt Cotton ◽

Plant Toxin ◽

Transgenic Bt Cotton ◽

Helicoverpa Armígera ◽

Lepidoptera Noctuidae

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Evaluating Cross-Resistance to Cry and Vip Toxins in Four Strains of Helicoverpa armigera With Different Genetic Mechanisms of Resistance to Bt Toxin Cry1Ac

Frontiers in Microbiology ◽

10.3389/fmicb.2021.670402 ◽

2021 ◽

Vol 12 ◽

Author(s):

Liangxuan Qi ◽

Hanyang Dai ◽

Zeng Jin ◽

Huiwen Shen ◽

Fang Guan ◽

...

Keyword(s):

Helicoverpa Armigera ◽

Genetic Basis ◽

Cross Resistance ◽

Bt Cotton ◽

Bt Toxin ◽

Field Control ◽

Helicoverpa Armígera ◽

Genetic Mechanisms ◽

Evolution Of Resistance ◽

Control Failures

Evolution of resistance by pests has diminished the efficacy of transgenic crops producing insecticidal proteins from Bacillus thuringiensis (Bt). In China, where transgenic cotton producing Bt toxin Cry1Ac has been planted since 1997, field control failures have not been reported but the frequency of resistance to Cry1Ac has increased in the cotton bollworm, Helicoverpa armigera. This provides incentive to switch to multi-toxin Bt cotton, which is grown in many other countries. Previous work created four laboratory strains of H. armigera with >100-fold resistance to Cry1Ac, with the genetic basis of resistance known in all but the LF256 strain. Here, we analyzed the genetic basis of resistance in Cry1Ac in LF256 and evaluated cross-resistance of all four strains to three toxins produced by widely planted multi-toxin Bt cotton: Cry1Fa, Cry2Ab, and Vip3Aa. DNA sequencing revealed that LF256 lacked the mutations in three genes (HaTSPAN1, HaABCC2, and HaABCC3) that confer resistance to Cry1Ac in two other strains of H. armigera we analyzed. Together with previous results, the data reported here show that each of the four strains examined has a different genetic basis of resistance to Cry1Ac. Significant positive cross-resistance occurred to Cry1Fa in three of the four strains tested but not to Cry2Ab or Vip3Aa in any strain. Thus, Cry2Ab and Vip3Aa are likely to be especially valuable for increasing the efficacy and durability of Bt cotton against H. armigera populations that have some resistance to Cry1Ac.

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Need for growing non-Bt cotton refugia to overcome Bt resistance problem in targeted larvae of the cotton bollworms, Helicoverpa armigera and Pectinophora gossypiella

Egyptian Journal of Biological Pest Control ◽

10.1186/s41938-021-00384-8 ◽

2021 ◽

Vol 31 (1) ◽

Author(s):

Muhammad Rafiq Shahid ◽

Muhammad Farooq ◽

Muhammad Shakeel ◽

Misbah Ashraf ◽

Zia Ullah Zia ◽

...

Keyword(s):

Helicoverpa Armigera ◽

Larval Mortality ◽

Pectinophora Gossypiella ◽

Bt Cotton ◽

Insect Larvae ◽

Plant Parts ◽

Arthropod Species ◽

Bt Resistance ◽

American Bollworm ◽

Helicoverpa Armígera

Abstract Background The effectiveness of Bacillus thuringiensis (Bt) cotton against target arthropod larvae is decreasing day by day. The comparative effect of Bt expression among Bt cotton varieties and different plant parts was observed against the cotton bollworms: Helicoverpa armigera and Pectinophora gossypiella larvae. Results In the present study, larval mortality of H. armigera was higher than P. gossypiella among selected Bt cultivars. Median lethal concentration (LC50) values were 8.91, 13.4, 14.0, and 36.4 for P. gossypiella, while 5.91, 4.04, 2.37, and 8.26 for H. armigera of FH-142, MNH-886, IR-3701, and FH-Lalazar, respectively. These values depicted that P. gossypiella had more Bt resistance problem than H. armigera larvae. The host range of both targeted insect larvae was different from each other due to the polyphagous feeding nature of the larvae of H. armigera that feed on different host plants, but P. gossypiella attacked only cotton with monophagous feeding habit. It was also notable from results that Bt expression in reproductive parts where the attacked pink bollworm was lower than the American bollworm, so the former had the maximum chance of resistance due to repeated exposure to Bt. Conclusions It was concluded that farmers be advised to follow the practice of growing non-Bt as a refuge crop to reduce the problem of Bt resistance in the target arthropod species.

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