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Amado Ramirez has had a great business idea. He lives in Oaxaca, where Mexicans have grown maize for thousands of years.

The potential of maize

People here in Oaxaca, in the rest of Mexico, and increasingly in the southern USA, eat tortillas, round maize pancakes, with every meal.

Maize is more than a food in Mexico - it is a way of life Amado Ramirez

"Maize is more than a food in Mexico, it's a way of life," Amado says in his spruce new tortilla shop Itanoni in Oaxaca city. "So I thought, why not make it a gourmet product, putting as much care and attention into making tortillas as chefs do into other delicacies."

To make his tortillas as authentic as possible, Amado has his own suppliers of maize grown on the mountainous slopes that surround the city. Then he grinds it and bakes it under strict supervision in his shop.

But now his business is facing disaster.

Discovering the GM link

Just as Amado is setting up his new shop, genetically modified ears of maize have been found in those same mountains he is hoping to use for his "pure" product.

Dr Chapela discovered the GM threat to maize in Oaxaca

The scientist who made the discovery is Ignacio Chapela. Originally from Mexico City, like many thousands of other Mexicans Dr Chapela has made a life for himself in the north, and is now a professor at the University of Berkeley in California.

He has been working with the campesinos or peasant farmers in the mountains of Oaxaca for more than 15 years. He has been helping them develop their communally held forests, and the small plots of land where they grow their maize and other crops to eat.

We had been planning to tell the farmers about a future threat - but found ourselves with a crisis situation already Dr Chapela

"It was late in 2000," Dr Chapela explains.

"I had planned to do a workshop in the Sierra de Juarez about GM crops. My assistant brought some GM maize from California, with the idea of contrasting it with the un-modified 'landraces' grown in Oaxaca."

"But he phoned me in California at about six in the morning, very excited. He had discovered that in the ears of maize grown in Oaxaca, more than 75 per cent had transgenic material. We had been planning to tell the farmers about a future threat, but found ourselves with a crisis situation already."

Publishing the results

Dr Chapela published his findings in Nature, the highly-respected worldwide scientific magazine in November 2001.

Maize - at the centre of this GM controversy

He claimed the maize found in Oaxaca contained the transgenic material p-35S, and genes from an insecticide bacterium to kill pests that are common in the US, but completely alien to the Mexican situation.

Since then, his results have been the source of dispute and controversy.

Controversy reigns

The first element of this controversy is how the GM maize got there. Since 1998, the Mexican government has banned the planting of GM maize, though, crucially, not the import of it. The country imports about two million tons of GM maize from the US each year. This is supposed to be eaten, not planted.

Olga is afraid her children will get cancer from eating maize

But this ban is impossible to police. When I visited the Sierra de Juarez, the local government store was selling ears of maize both for food and for planting. One local farmer, Olga Toro Maldonado, did what many of her neighbours did.

"The ears of maize for sale looked good. I was curious, so I planted a few in my milpa (maizefield). They produced a good crop, so I planted more of them the next year."

It is here the experts disagree with Dr. Chapela's version of the threat from transgenic maize.

Julien Berthaud is a maize expert with the International Centre for the Improvement of Maize and Wheat, based outside Mexico City.

Julien Berthaud needs further research before he believes there is a threat

"First, we have to do more extensive and independent tests to see if Dr. Chapela was right," he says. "But even so, we think that this genetically modified material does not pose a threat, because it performs no function as a pesticide in Mexico, the introduced gene sequence will have no effect, and will probably disappear."

The scientific arguments swirl to and fro. But back at the Itanoni tortilla shop in Oaxaca city, the customers are definitely worried.

Future is threatened

"Yes, I do like this local maize," Maria Dolores tells me. "But there are rumours that it has been contaminated, that it could give you cancer, and I'm not so sure about eating too much of it."

And while his customers see this kind of threat even in his products, Amado Ramirez's dreams of a new Mexican empire based on its most famous staple food could come to nothing.

Also in this week's Crossing Continents:

Women in Juchitan "rule the roost"

A report on the town where women rule the roost and most gay men are transvestites.

Mexico: Thursday 14 March 2002 at 1100 GMT on BBC Radio Four

Reporter: Nick Caistor
Producer: Arlene Gregorius
Editor: Sue Ellis