Syngenta boss Davor Pisk has backed forecasts of huge yield gains from genetically modified foods that US officials believe may undermine commodity prices.

"There are companies talking of taking corn yields from 150 bushels per acre to 300 bushels per acre in 20 years time," Mr Pisk, the head of the Swiss giant's seeds division, told the World Agri Invest Congress in London.

"I think that is entirely feasible."

The comments follow a warning from Joseph Glauber to the same conference that the yield claims being made by some seed groups threatened long-term forecasts of robust crop prices.

Regulatory 'bottleneck'

However, Mr Pisk added that wheat was being left out of the loop for genetically modified "improvement", noting the reluctance of Europe, a huge growing area for the crop, to embrace the technology.

It was beholden to all seed groups to assess what scope genetically modified seeds had for giving a satisfactory return on their large development costs.

But politics was "getting in the way" of getting seeds onto the market in Europe, causing a regulatory "bottleneck" of GM applications waiting for clearance.

"Everyone knows that this (GM technology) a controversial issue," he added.