Each year, thousands of acres（英亩） of crops are planted throughout Africa, Asia and Australia only to be laid to waste by a parasitic¹（寄生的） plant called Striga（独脚金） , also known as witchweed. It is one of the largest challenges to food security in Africa, and a team of scientists led by researchers from the University of Toronto have discovered chemicals and genes² that may break Striga's stranglehold（束缚） . When crops grow, their roots release a plant hormone³ called strigolactone. If the soil contains Striga seed, it will use the released strigolactone as a cue to germinate⁴（发芽，生长） and infect the crop plants. Once connected to the crop, the Striga plant kills the crop by sucking out its nutrients⁵. "In sub-Saharan Africa alone, Striga has infected up to two-thirds of the arable⁶ land（耕地） ," says U of T cell and systems biologist Peter McCourt, principle investigator⁷ of a study published this week in Nature Chemical Biology. "With chemicals and genes in hand that influence strigolactone production in plants, we should be able to manipulate the level of this compound by chemical application or plant breeding which would break the Striga-crop interaction.

The scientists used a model genetic⁸ plant system called Arabidopsis to screen 10,000 compounds and identify a set of five chemicals, designated cotylimides, which increase the accumulation of strigolactone in plants. They also found related chemicals that decrease strigolactone levels. From there, they screened for mutants of Arabidopsis that were resistant⁹ to cotylimides and identified mutants that made less strigolactone. These mutants identified genes that regulate strigolactone levels in plants.