Dehydrocostus lactone is exuded from sunflower roots and stimulates germination of the root parasite Orobanche cumana

► Dehydrocostus lactone is exuded by sunflower roots. ► This guaianolide sesquiterpene lactone acts as interspecific chemical signal. ► Like strigolactones, it stimulates germination of root parasitic weeds. ► Its biosynthesis is inhibited by mevastatin and not by fluridone. ► Phosphate starvation reduces its production.