A controversial outdoor experiment with genetically modified (GM) wheat has been hailed a success, says the Federal Institute of Technology in Zurich.
But a lengthy legal battle and extra security needed to protect the site from protesters caused the project to burst its original budget threefold.
The test, conducted at Lindau near Zurich, confirmed laboratory results that the KP4 gene improved wheat's resistance to fungi by 10 per cent.
Safety tests on pollen distribution and soil analysis also showed that the GM wheat posed no increased risk to humans or the environment, according to project leader Christof Sautter.
Sautter told swissinfo that it was vital to carry out the tests in the open air and predicted that similar trials may take place in Switzerland in the future.
"You can simulate temperature, humidity and light conditions indoors, but you can never simulate the complex interaction with other organisms and the soil," he said. "There really is no alternative.
"Sooner or later there will be someone in Switzerland asking to conduct a similar field test, but nothing is known at the moment. It will not be me as I cannot afford another experience like that – it was too stressful."
The environmental organisation Greenpeace, which opposed the trial both in the courts and with a demonstration at the site, warned that it has set a dangerous precedent.
"Dr Sautter has said there will probably be more trials to follow this one," said spokesman Yves Zenger. "We will continue to oppose these risky experiments.
"We are disappointed that our opposition was not taken seriously this time. No one knows how GM crops will influence the environment in the long term."
Residents around the experiment zone remain worried about the effects of the trial for local farmers.
"Our farming community is at risk," said Kurt Schweizer of the group "Lindau against GM Wheat". "Even if there is just a rumour of contamination, they will not be able to sell their products.
"We just hope that [the institute] is right and they have kept the foreign genes within the experiment field."
Ulrich Suter, vice-director of research at the institute, said the project's budget had mushroomed from SFr350,000 ($280,000) to SFr950,000 to pay for legal costs, delays, policing and a private security firm to patrol the site.
But he denied the institute had ignored protestors, insisting that all the relevant information had been made available.
"We were aware of the opposition, but the researchers had proved that the experiment was of a scientifically high value, complied with the laws and had obtained all the necessary approval from the government," Suter told swissinfo.
"Political opposition is not a sufficient reason to stop an important experiment."
Sautter added that he could not understand the protests. "I would appreciate plants that need less chemicals," he said. "From a scientific point of view there is no need for this opposition to gene technology."
swissinfo, Matthew Allen in Zurich
The field experiment on genetically modified wheat was carried out by the Federal Institute of Technology in Zurich between 18 March and 14 July, 2004.
The wheat's resistance was tested against smut fungi (Ustilaginales).
Sixteen safety tests were carried out to ensure the trial complied with the Swiss law on genetic engineering.