WASHINGTON (AP) – Concerned that genetically modified plants will spread their genes to related crops in nearby fields, researchers have developed a system aimed at preventing such crossbreeding.

It’s a method they hope, with further refinement, will allow farmers to reseed crops yearly without worry about affecting nonmodified crops.

Biotech crops are a growing proportion of American agriculture. The Agriculture Department estimates 38 percent of the corn planted this year will be genetically engineered and 80 percent of soybeans will be a biotech variety.

While American consumers generally seem to accept biotech foods, Europeans doubt their safety. A European Union moratorium on U.S. biotech imports has been in place for four years, costing the United States $300 million annually in corn exports.

And that ban raises concerns about biotech crops cross-pollinating related plants in nearby fields, rendering those crops also unsuitable for export.

The new system for preventing crossbreeding, developed by a team of researchers led by Johann P. Schernthaner at Canada’s Eastern Cereal and Oilseed Research Center in Ottawa, is reported in the online edition of Proceedings of the National Academy of Sciences.

While the system was developed using tobacco, Schernthaner said he believes it would work for most crops, although “the genetic components involved would have to be assessed for suitability on a case by case basis.”

The findings do show, he said, “that the containment of transgenes is possible in an agricultural setting and that environmental concerns … can be addressed in a simple fashion.”

Doug Gurian-Sherman, science director for biotechnology at the Center for Science in the Public Interest, said there “are pros and cons to this from our perspective” but it is technology that should be explored.

“The big question is how it’s applied,” he said.

Agronomy professor T. Wayne Pfeiffer of the University of Kentucky said that while the system worked to some degree, the process used seems “impractical in a seed production system for a seed reproduced crop.”

“The paper doesn’t explain how the system would be maintained in 100 percent of the seeds in subsequent generations,” he added, “so I do not see this as a magic system to prevent the spread of transgenes in all crops.”

In the Canadian research, the team first inserted a “seed lethality” gene that prevents seeds of the plant from germinating, although the plants had normal growth and seed production.

They then crossed this plant with another that had an added gene that represses the seed lethality gene.

The offspring of the two produced a plant with viable seeds that could continue to propagate indefinitely through self-pollination. But when these plants were crossed with normal tobacco plants the seed lethality gene and the suppressor gene were separated and the resulting seeds would not grow.

While the system has been demonstrated in the laboratory, Schernthaner and Steven Fabijanski, one of his co-authors, said it needs to be refined and tested thoroughly for actual field use.

“In particular, the repression of the (seed-lethality) component would have to be made watertight,” they said.

In addition, they said a second genetic component probably is needed to be sure of containing the repressor gene.