In a laboratory at Monsanto's headquarters in St Louis, Missouri, US, a robot arm works its way through hundreds of DNA samples, adding chemicals, shaking, analysing results and churning out computer data.

Each tiny well contains a chunk of DNA, incubated with plant tissue, and an insect in some stage of development that normally feeds on the plant.

The robot shuttles back and forth, performing systematic tests. At the end of the day, it prints out a ream of data for the scientists to look at.

Eventually, after innumerable tests, one of these biological production lines might come up with what Monsanto is looking for - say, a gene that shows promise in controlling insects on a given plant, or, perhaps, in another research lab, a gene that might alter the fat profile of corn making it better for the heart.

Biological goldrush

Gene traits, Monsanto believes, will form the bulk of its biotechnology business in coming years. Its $1bn research centre is dedicated to this biological goldrush, identifying and isolating genes that confer a beneficial trait, then inserting the gene into a given plant.

It takes tens of millions of dollars and at least 10 years' work to turn basic science - inserting a desired gene into a plant - into a marketable product: seed containing the new genetic characteristic.

Click here to see how a plant is given a new genetic characteristic

Once a desired gene has been selected, the gene is transferred into the plant in the laboratory using one of two different techniques. One way is introduce the DNA into the plant using a common bacterium known as Agrobacterium.

The other method is to literally blast DNA, coated on tiny particles of gold dust, into plant cells growing in the laboratory using a so-called "gene gun".

Click here to see the next stage of plant genetic engineering

Once the new gene has been inserted, using either technique, the modified plant cells undergo tissue culture. They reproduce, and grow into new plantlets. Eventually, the plantlets can be transferred into soil.

So far this technology has been used to produce commercial crops aimed at the farmer.

One main approach has been to engineer the likes of potato, corn and cotton to produce their own insecticides via a toxin-producing gene from the soil bacterium Bacillus thuringiensis (Bt).

The other main approach has been to develop crops that are resistant to herbicides, allowing farmers to apply chemical sprays that kill weeds not crops.

The GM loaf

The next product of the biotech revolution, at least in the US, is likely to be genetically modified wheat. Monsanto's spring-sown variety has been engineered to confer resistance to Monsanto's Roundup weedkiller. Field trials are now underway in North and South Dakota, Montana and Minnesota.

"We are hopeful that there will be a commercial launch between 2003 and 2005 of RoundUp Ready spring wheat in North America only," says Monsanto's Mark Buckingham.