Aphids mount multiple defence strategies to resist insecticides
28 June 2010
The peach potato aphid, Myzus persicae is the most important aphid pest of crops in many regions of the world due to its large host range and the damage it causes through direct feeding and its ability to transmit more than 100 plant viruses. This species has developed resistance to most insecticides although a class of compounds called the neonicotinoids have remained an effective and popular control measure. However, recent cases of neonicotinoid resistance in M. persicae represent a threat to the long-term effectiveness of these insecticides as well.
Work on other insect species has shown that resistance can arise through increased production of metabolic enzymes called cytochrome P450s that detoxify the insecticide. A new study of neonicotinoid resistance in M. persicae, published in PLOS genetics by scientists at Rothamsted Research, an institute of BBSRC, and collaborators at University College London, is the first to find resistance associated with an increase in the number of copies of a P450 gene in a major agricultural pest.
The study made use of recent advances in genomics to investigate all genes encoding detoxification enzymes in a resistant strain of M. persicae. Dr Chris Bass, who led the genomics research said, 'This study builds on the work of Graham Moores and Despina Philippou at Rothamsted, who provided strong evidence of a role for P450-mediated detoxification in resistance*. Now we have demonstrated that resistance is associated with multiple duplications of a single P450 gene, with the resistant aphids carrying ~18 copies of the gene compared to the normal 2 copies found in susceptible aphids.' This may enable aphids to rapidly breakdown insecticides and so avoid death.
Genomic analyses also revealed that several genes encoding proteins that make up the insect cuticle are over-expressed in resistant aphids. The paper's lead author, Dr Mirel Puinean said, 'This suggests that an increase in the production of cuticular proteins in resistant aphids could reduce the amount of neonicotinoids that penetrate the insect's body and our biochemical assays supported this.' However, further work is needed to discover exactly how the increased production of cuticular proteins boosts the body armour of aphids that are resistant to insecticides.
Levels of neonicotinoid resistance currently being reported are insufficient to impair the field effectiveness of these insecticides. However, this work highlights the remarkable capacity of aphids to adapt and the need for continued research and informed management strategies to prevent resistance becoming more potent and widespread.
Notes to editors
This paper is published in PLOS genetics as "Amplification of a cytochrome P450 gene is associated with resistance to neonicotinoid insecticides in the aphid Myzus persicae" by Alin M. Puinean, Stephen P. Foster, Linda Oilphant, Ian Denholm, Linda M. Field, Neil S. Millar, Martin S. Williamson and Chris Bass (Please see http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1000999).
This work was funded as part of an Institute Career Path Fellowship award to Dr Chris Bass by BBSRC and a BBSRC Industrial Partnership Award to Dr Ian Denholm, Martin Williamson and Professor Lin Field at Rothamsted Research and Professor Neil Millar at UCL.
*See also: Philippou D, Field LM, Moores GD (2009) Metabolic enzyme(s) confer imidacloprid resistance in a clone of Myzus persicae (Sulzer) (Hemiptera: Aphididae) from Greece.
Pest Manag Sci 66: 390-395. (http://www3.interscience.wiley.com/journal/123193309/abstract)
Guidelines on managing resistance in M. Persicae have been published by the Insecticide Resistance Action Group (IRAG).
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