September 2, 2009

Garlic mustard plants can lose toxicity

U.S. scientists have discovered the invasive garlic mustard plant, over time, loses its primary weapon -- a fungus-killing toxin it injects into the soil.

University of Illinois scientists said their study is one of the first to show evolutionary forces can alter the very attributes that give an invasive plant its advantage.

Garlic mustard plants are part of the family that includes cabbage and horseradish -- plants that rely on soil fungi for phosphorous, nitrogen and water.

For whatever reason (garlic mustard) plants just don't hook up with the soil fungus, said postdoctoral researcher Richard Lankau, who led the study with plant ecologist Greg Spyreas.

Instead, garlic mustard produces glucosinolates -- pungent compounds that leach into the soil and kill soil fungi, thereby weakening native plants, Lankau said. As a result, garlic mustard now grows in dense patches in many North American woodlands, its preferred habitat.

Lankau and his team discovered the levels of glucosinolates in the plant begin to diminish once the garlic mustard vanquishes most of its competitors.

Spyreas said genetic studies suggest the diminished glucosinolates production is the result of natural selection -- plants producing less of the toxin are more likely to survive and reproduce in older populations.

The research that also included Adam Davis of the U.S. Department of Agricultural is reported in the Proceedings of the National Academy of Sciences.