Thursday, 31 July 2008

GM and insecticides reduce mycotoxins in crops

European Corn Borer hatchlings
Food crops can become infested with insects which will reduce the yield of the crop - bad enough news for the farmer but it gets worse. A heavily chewed plant such as maize becomes susceptible to infection by fungi including aspergillus and that fungus can start to synthesise mycotoxins:
"How severely a maize plant is infected with fungi and whether this leads to mycotoxins being produced depends on a large number of factors. Humidity and temperature during the growing season, soil cultivation and the susceptibility of the variety in question all play a role, as does the time chosen for harvesting. The complex process, which is not fully understood, makes it difficult to control mycotoxin formation in individual cases and to reduce contamination reliably. Studies in Germany, for instance, have shown that mycotoxin levels vary widely between individual maize plants, even on the same site. There are many indications that stress – both for the maize and for the fungus – results in higher mycotoxin production"
As the infestation gets worse so the levels of mycotoxin get worse:
"But it is also clear that a heavy infestation of chewing pests leads to higher mycotoxin contamination. In many maize-growing regions of Europe the European corn borer is the main maize pest: the larvae bore their way into the maize plants, leaving holes through which Fusarium and other fungi can enter."
Mycotoxins can be extremely toxic so their levels are strictly controlled in food for both animals and humans.

Prevention of insect infestation effectively reduces the levels of mycotoxin in the crop, introducing a greater level of control over toxin levels.
"The more effectively the corn borer is controlled, the fewer chewing sites there are that can be used by the fungal pathogens to colonize the maize plant, in addition to the stigma route."

Certain genetically manipulated crops (e.g. Bt Maize) are effective at controlling insects without the aid of chemical insecticides and it has been shown that these crops also suffer from far lower levels of mycotoxin contamination:
"On all sites, the Bt maize varieties used showed the best results: only isolated corn borers were found in the crops. On almost all the trial fields the mycotoxin values measured were lower in the Bt maize plants than in the conventionally grown control plants."
The GM crop therefore benefits from both increased yield and lower toxin levels - two benefits for the price of a single modification.

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