THE environment could be under threat from an unexpected source. If the
inedible parts of new breeds of crop plants contain abnormal levels of
substances such as sugars, they could attract different insects and upset the
local ecology, says a plant biotechnologist from Illinois.
Such changes are not currently monitored in either genetically modified or
conventionally bred plants. Regulators look primarily for potential alterations
in the produce of the plant, such as tomatoes or potatoes. It鈥檚 even less likely
that these changes would be picked up in conventionally bred plants, as they do
not have to be checked as thoroughly as GM produce.
David Lightfoot of Southern Illinois University at Carbondale outlined his
concerns last week during a conference on crop plants at the University of Wales
in Aberystwyth. He urges plant breeders to apply the same 鈥渟ubstantial
equivalence鈥� tests to inedible tissue as to the edible parts.
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The principle of substantial equivalence is applied mainly to GM produce.
Plant breeders must convince the regulators that a new GM tomato, for example,
is virtually indistinguishable in composition from its conventionally bred
counterpart.
Lightfoot鈥檚 concerns about inedible tissues arose after he equipped tobacco
and maize plants with a bacterial gene to increase the uptake of nitrogen from
the soil.
When he looked at the leaves and roots, he found the expected doubling in
concentrations of amino acids. But to his surprise, he also found a doubling of
sugar levels elsewhere in the plant. 鈥淚f you鈥檙e making more amino acids, they
draw on the sugars so concentrations should have gone down, not up,鈥� he
says.
鈥淭he changes only occurred in the leaves and roots, but not in the tobacco
seeds or the edible maize seeds, which were normal in composition,鈥� he adds. So
while maize seeds would have passed the substantial equivalence test, the
abnormal leaves and roots would have been missed.
Lightfoot stresses that his nitrogen-guzzling plants could bring major
environmental benefits. They increased yields by 5 to 10 per cent and were less
susceptible to drought. But the altered leaves and roots deserve scrutiny too,
he says.
He suggests using DNA analysis to compare the activities of thousands of
genes in new and parent plant varieties. But he admits such tools are still
experimental. For now, he says that breeders should only test inedible parts of
plants if they suspect dramatic changes.
Bill Timberlake, the chief technical officer of Monsanto in St Louis,
Missouri, disagrees. 鈥淚t wouldn鈥檛 be worth the effort because the data would be
uninterpretable, and it would be very expensive,鈥� he says.
But Sue Mayer of GeneWatch UK, an environmental lobby group based in Buxton,
Derbyshire, says that such analyses could prevent costly environmental problems.