Corn, soy yields gain little from genetic engineering

The use of genetically engineered corn and soybeans in the US for more than a decade has had little impact on crop yields despite claims that they could ease looming food shortages, according to a study.

"A hard-nosed assessment of this expensive technology's achievements to date gives little confidence that it will play a major role in helping the world feed itself in the foreseeable future," said the report by the Union of Concerned Scientists.

The study evaluated the effect on corn and soybean crop yields of genetically engineered varieties commercialised in the US over the past 13 years, examining peer-reviewed academic studies that date back to the early 1990s.

"Based on that record, we conclude that GE (genetic engineering) has done little to increase overall crop yields," it said.

The report said genetically engineered soybeans account for 90 per cent of soybeans grown in the US, while genetically engineered corn accounts for 63 per cent of the US corn crop.

"Overall, corn and soybean yields have risen substantially over the last 15 years, but largely not as a result of the GE traits," the report said. "Most of the gains are due to traditional breeding or improvement of other agricultural practices."

It found that corn and soybeans that were genetically modified to increase their tolerance to herbicides "have not increased operational yields, whether on a per-acre or national basis, compared to conventional methods that rely on other available herbicides".

Corn modified with genes from Bt, or Bacillus thuringienisis, bacteria for resistance to several kinds of insects, did provide higher yields, but the study estimated the increase at between 0.2 and 0.3 per cent a year on average over the past 13 years.