Plant biosensor could help African farmers fight parasitic witchweed

Engineering and biology professors at the University of Toronto have developed a new strategy for helping African farmers fight a parasitic plant that devastates crops.

Plants in the genus Striga, also known as witchweed, act as parasites of other plants, tapping into their root systems and hijacking them for their own purposes. Though their purple flowers are pretty to look at, a field full of Striga plants is in fact a nightmare for a farmer who wants to grow corn, sorghum, rice or other subsistence crops. The problem affects more than 100 million people across 25 countries in sub-Saharan Africa.

U of T chemical engineering professor Alexei Savchenko, along with professor Peter McCourt in the Department of Cell and Systems Biology, have created a genetically engineered plant biosensor, a tool that will help them hunt for molecules that could prevent Striga infestations.

Savchenko and McCourt hope to outwit Striga by tricking its chemical senses. Their idea is to spray the ground with a chemical similar to the plant hormones that Striga is primed to detect. "You would spread this false signal and cause the Striga to germinate," says Savchenko. "Then you would destroy the Striga and plant the crops in a clean field."

Firstly, McCourt's group identified which receptors are most sensitive to the hormones and thus the most important ones to focus on.

The next step was to clone and introduce the most sensitive receptor into Arabidopsis thaliana, a small plant commonly used as a model organism in biology studies. Unlike Striga, Arabidopsis is not a parasite, so it's much easier to grow, yet the genetically engineered plant now reacts to crop hormones and their chemical cousins in the same way that Striga would.