27 February 1998



GM crops promise both

husbandry and marketing

benefits. But could they

cause contamination

problems on the farm?

Edward Long reports

GENETICALLY modified crops targeted at high volume and high value, food and non-food markets are set to have a huge impact on arable farming.

But can growers manage these "new" crops so there are no adverse effects on other crops in the rotation?

According to Frank Oldfield, who chairs the HGCAs oilseeds R&D committee and manages the 2200ha (5434-acre) Raynham Farm Company at East Raynham, Fakenham, Norfolk, they certainly can.

"There is absolutely no doubt that GM crops will have a huge impact on farming. New technology has been developed that will persuade existing crops to produce the specific raw materials needed by industry, as well as allowing the insertion of characters to make them easier, cheaper, and more reliable to grow."

Huge new markets could open up if crops can be converted into raw materials for industry.

The first wave of GM crops will include rape transformed to produce stearic acid for food manufacturers and lauric acid for soap and detergent makers, says Mr Oldfield. Such crops are already being grown on European farms.

Second wave

The second wave of "new" crops will include herbicide-tolerant types. Further off are rapes which produce the raw materials for biodegradable plastics, high temperature plastics, cosmetics, shampoos and pharmaceuticals.

Sugar beet and potatoes modified to produce a range of industrial raw materials are also due.

"The biggest problem with GM crops, particularly rape but possibly the others as well, is the risk of a seed bank building-up in the soil due to seed dormancy," says Mr Oldfield.

That could lead to volunteers to contaminate other crops and may reduce weed control options.

With that in mind it is vital to prevent dormant seed getting into the soil at harvest. "Shed seed must not be buried."

HGCA-funded research by Dr Peter Lutman at IACR Rothamsted shows the best approach is to leave seed on the surface until it chits before cultivating or ploughing stubbles.

Once the subsequent cereal crop has emerged, any further unwanted rape weeds must be removed at the seedling stage using a low dose of hormone weedkiller such as CMPP.

A follow-up treatment in the spring using new CMPP when the crop reaches growth stage 32 will provide a final sweep-up of late germinators, advises Mr Oldfield.

Contamination of adjacent rape crops and related weeds by GM rape pollen is also a concern.

The French oilseeds organisation CETIOM is checking that in France, as well as the rotational implications of introducing GM rape, sugar beet, potatoes, maize and soya. All effects within 0.6 miles (1km ) of the site are being measured.

The French trials should show up any new measures needed to avoid trouble in the field, and after harvest, says Mr Oldfield. "A similar in-depth project should be conducted in the UK.

"Cross pollination is a worry, but so far there is no concrete evidence that GM crops have ever contaminated non-modified plants or wild species," he says.

"Until detailed research has been done we must rely on isolation to prevent any potential trouble, however small the risk. Modified rape must not be grown within 400m of other brassicas."

Policy has precedent

That type of approach is not unprecedented. When double-low rapes replaced high erucic types in the 1970s there was concern about the risk of cross-contamination. But good hygiene prevented problems, Mr Oldfield notes.

This time the possible contaminant is reversed, coming from the introduced GM crop and not the superseded conventional crop.

If GM crops are to succeed those transformed to produce industrial raw materials must be kept separate our of food crops, Mr Oldfield says. "Even the slightest hint of a mix-up is likely to lead to rejection, possibly rendering the crop unsaleable.

"The new technology could open up vast new markets for farm produce, so it is vital that GM crops are managed properly and nothing is done to compromise their potential, or to reduce efficient food production," Mr Oldfield concludes. &#42

Genetically engineered oilseed rape varieties offer much potential. But how easy is it to avoid cross-contamination and volunteer problems?

GM crop care will be worth it, says Frank Oldfield, chairman of the HGCAs R&D commitee.


&#8226 Novel properties offer scope for improved profits.

&#8226 BUT risk of contamination of conventional crops.

&#8226 Soil seed-bank biggest threat.

&#8226 After harvest chit shed seed before cultivating and remove volunteers with autumn and spring herbicides.

&#8226 Keep GM rape crops 400m clear of other brassicas.

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