New research has shown that genetically modified (GM) subterranean clover is unlikely to be more of a weed threat than conventional subterranean clover.

As part of a wider CSIRO study into genetically modified organisms (GMOs), CSIRO Plant Industry studied the environmental risk of GM subterranean clover (sub-clover) as a potential weed in remnant native grasslands.

"Our field and glasshouse trials provided no evidence that the invasiveness and competitiveness of GM sub-clover was any greater than conventional sub-clover, indeed at higher densities GM sub-clover performs less well," Dr Bob Godfree of CSIRO Plant Industry says.

Conventional sub-clover is a common pasture plant that can occur in native grasslands. To improve its nutritional quality researchers have added a sunflower gene to increase its protein.

Weediness was determined by comparing seed germination rates, plant growth, seed production, seed weight and seed dormancy between a GM and non-GM sub-clover.

"We found that GM sub-clover seed tended to be 'softer' so slightly less dormant meaning more seed was 'released' from the seed bank and could germinate every year," Dr Godfree says.

"In a good year 'soft' seed is an advantage as the largest number of seed can grow in the favourable conditions but in a poor year it's a disadvantage as much of the seed is wasted that year leaving a limited amount for the following season."

"Overall it was clear that in native grassland situations GM sub-clover populations would decline over time and in pastures both GM and non-GM sub-clover might persist."

There are no plans to generally release the GM sub-clover. This study helps improve the understanding of the ecology of GM plants and how they may differ from their conventional counterparts.

All gene technology research at CSIRO is approved by the Office of the Gene Technology Regulator. This research is done in collaboration with the Centre for Plant Biodiversity Research.