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Environment & Energy
Related: About this forumTrouble on the Horizon for GM Crops?
http://uanews.org/node/47788[font face=Serif][font size=5]Trouble on the Horizon for GM Crops?[/font]
By Daniel Stolte, University Communications, June 19, 2012
[font size=4]Pests are adapting to genetically modified crops in unexpected ways, researchers have discovered. The findings underscore the importance of closely monitoring and countering pest resistance to biotech crops.[/font]
[font size=3]Resistance of cotton bollworm to insect-killing cotton plants involves more diverse genetic changes than expected, an international research team reports in the journal Proceedings of the National Academy of Sciences.
To decrease sprays of broad-spectrum insecticides, which can harm animals other than the target pests, cotton and corn have been genetically engineered to produce toxins derived from the bacterium Bacillus thuringiensis, or Bt.
A major surprise came when the team identified two unrelated, dominant mutations in the field populations. "Dominant" means that one copy of the genetic variant is enough to confer resistance to Bt toxin. In contrast, resistance mutations characterized before from lab selection are recessive meaning it takes two copies of the mutation, one provided by each parent, to make an insect resistant to Bt toxin.
"Dominant resistance is more difficult to manage and cannot be readily slowed with refuges, which are especially useful when resistance is recessive," Tabashnik said.
[/font][/font]
By Daniel Stolte, University Communications, June 19, 2012
[font size=4]Pests are adapting to genetically modified crops in unexpected ways, researchers have discovered. The findings underscore the importance of closely monitoring and countering pest resistance to biotech crops.[/font]
[font size=3]Resistance of cotton bollworm to insect-killing cotton plants involves more diverse genetic changes than expected, an international research team reports in the journal Proceedings of the National Academy of Sciences.
To decrease sprays of broad-spectrum insecticides, which can harm animals other than the target pests, cotton and corn have been genetically engineered to produce toxins derived from the bacterium Bacillus thuringiensis, or Bt.
A major surprise came when the team identified two unrelated, dominant mutations in the field populations. "Dominant" means that one copy of the genetic variant is enough to confer resistance to Bt toxin. In contrast, resistance mutations characterized before from lab selection are recessive meaning it takes two copies of the mutation, one provided by each parent, to make an insect resistant to Bt toxin.
"Dominant resistance is more difficult to manage and cannot be readily slowed with refuges, which are especially useful when resistance is recessive," Tabashnik said.
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Trouble on the Horizon for GM Crops? (Original Post)
OKIsItJustMe
Jun 2012
OP
snot
(10,530 posts)1. Since pests have a much shorter life-cycle than humans,
they'll evolve tolerance of the built-in poisons long before we do.
OKIsItJustMe
(19,938 posts)2. Or… put another way…
They have evolved tolerance much faster than we will.
Nihil
(13,508 posts)4. Worryingly accurate comment there OK. (n/t)
FogerRox
(13,211 posts)3. Resistance to Monsantos BT corn
Took about 8 years to show. And only seems to effect that particular strain of Bt in corn. This study seems to find bad news Re: Bt genetic modded products- cause of Dominant resistance.
OKIsItJustMe
(19,938 posts)5. From the study…
http://dx.doi.org/10.1073/pnas.1200156109
[font face=Serif][font size=5]Diverse genetic basis of field-evolved resistance to Bt cotton in cotton bollworm from China[/font]
[font size=4]Abstract[/font]
[font size=3]Evolution of pest resistance reduces the efficacy of insecticidal proteins from Bacillus thuringiensis (Bt) used in sprays or in transgenic crops. Although several pests have evolved resistance to Bt crops in the field, information about the genetic basis of field-evolved resistance to Bt crops has been limited. In particular, laboratory-selected resistance to Bt toxin Cry1Ac based on recessive mutations in a gene encoding a toxin-binding cadherin protein has been identified in three major cotton pests, but previous work has not determined if such mutations are associated with field-selected resistance to Bt cotton. Here we show that the most common resistance alleles in field populations of cotton bollworm, Helicoverpa armigera, selected with Bt cotton in northern China, had recessive cadherin mutations, including the deletion mutation identified via laboratory selection. However, unlike all previously studied cadherin resistance alleles, one field-selected cadherin resistance allele conferred nonrecessive resistance. We also detected nonrecessive resistance that was not genetically linked with the cadherin locus. In field-selected populations, recessive cadherin alleles accounted for 7584% of resistance alleles detected. However, most resistance alleles occurred in heterozygotes and 5994% of resistant individuals carried at least one nonrecessive resistance allele. The results suggest that resistance management strategies must account for diverse resistance alleles in field-selected populations, including nonrecessive alleles.
Conflict of interest statement: B.E.T. has received support for research that is not related to this publication from the following sources: Cotton Foundation, Cotton Inc., National Cotton Council, Monsanto, and Dow AgroSciences. B.E.T. is also a coauthor of a patent on engineering modified Bt toxins to counter pest resistance, which is related to research described by Tabashnik et al. (2011) Nature Biotechnology 29:11281131.
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[font size=4]Abstract[/font]
[font size=3]Evolution of pest resistance reduces the efficacy of insecticidal proteins from Bacillus thuringiensis (Bt) used in sprays or in transgenic crops. Although several pests have evolved resistance to Bt crops in the field, information about the genetic basis of field-evolved resistance to Bt crops has been limited. In particular, laboratory-selected resistance to Bt toxin Cry1Ac based on recessive mutations in a gene encoding a toxin-binding cadherin protein has been identified in three major cotton pests, but previous work has not determined if such mutations are associated with field-selected resistance to Bt cotton. Here we show that the most common resistance alleles in field populations of cotton bollworm, Helicoverpa armigera, selected with Bt cotton in northern China, had recessive cadherin mutations, including the deletion mutation identified via laboratory selection. However, unlike all previously studied cadherin resistance alleles, one field-selected cadherin resistance allele conferred nonrecessive resistance. We also detected nonrecessive resistance that was not genetically linked with the cadherin locus. In field-selected populations, recessive cadherin alleles accounted for 7584% of resistance alleles detected. However, most resistance alleles occurred in heterozygotes and 5994% of resistant individuals carried at least one nonrecessive resistance allele. The results suggest that resistance management strategies must account for diverse resistance alleles in field-selected populations, including nonrecessive alleles.
Conflict of interest statement: B.E.T. has received support for research that is not related to this publication from the following sources: Cotton Foundation, Cotton Inc., National Cotton Council, Monsanto, and Dow AgroSciences. B.E.T. is also a coauthor of a patent on engineering modified Bt toxins to counter pest resistance, which is related to research described by Tabashnik et al. (2011) Nature Biotechnology 29:11281131.
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