London (19.2.08)
– One of the consequences of insect attacks on crop plants is a secondary
invasion by the fungi which gain access though the wounds left by the insects.
Some fungi produce very toxic compounds which may have devastating effects
of humans and animals eating the contaminated products.
Mycotoxins (1) are widely regarded as amongst the most serious of naturally
occurring toxins that can contaminate our food supply. With the potential
to affect both primary and processed foodstuffs, it is essential that a broad
approach is taken at all stages of the food chain with regard to risk assessment,
detection, prevention and control. Maize is one of the crops so affected.
The problem of controlling the insects is exacerbated by the rapidity with
which they gain access. Farmers need to be on the alert for insect presence
as soon as they hatch in order to spray with insecticide; once they enter
into the plant tissues, the insects are protected and it may be too late;
the fungi are then able to infect through the insect entry holes.
One of the expected benefits of using Bt-crops, in which the plants themselves
contain an insecticide derived from a soil bacterium and harmless to higher
animals, was to minimise insect attack with fungal colonisation. This is indeed
confirmed by experience.
A new study, surveying the incidenece of a range of myctoxins in North America
and Europe, offers overwheming evidence that Bt maize contains lower levels
of fumonisin, deoxynivalenol and zearlenone than non-Bt maize with a similar
genetic constitution (isolines) (2). The more extensive work on aflatoxin
reduction yielded mixed results but new varieties of Bt-maize that may be
commercialised soon are likely to have a more significant impact on aflaotxin
levels.
Sources:
1. See Selected Recent IUPAC Mycotoxin References and Publications.
US Food and Drug Administration (last update 4.12.07) (http://www.cfsan.fda.gov/~frf/iuprefs.html)
2. Felicia Wu (Feb. 2008). Field evidence: Bt corn and mycotoxin reduction.
ISB News Report (http://www.isb.vt.edu/news/2008/news08.feb.htm#feb0803)
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