Recent Achievements in the Bio-control of Orobanche Infesting Important Crops in the Mediterranean Basin

Orobanche spp. (broomrapes) are holoparasitic plants distributed predominantly in the Northern Hemisphere parasitizing the roots of a range of plant species mainly in wild ecosystems. Orobanche species cause severe yield reduction of many important crops. There are only very few herbicides which are able to selectively control broomrapes and different approaches have been put forward to develop natural product based pesticides to control Orobanche. Several phytopathogenic fungi were evaluated for their use as potential mycoherbicide and for ability to produce toxic metabolites which could be applied as herbicides. Using the alternative approach "suicidal germination", interesting results were obtained by testing two microbial metabolites (fusicoccins and ophiobolin A) especially with Orobanche species whose germination is not induced by the synthetic strigolactone GR24. From pea root exudates, peagol and peagoldione, close related to strigolactones, and three polyphenols, named peapolyphenols A-C, together with already well known polyphenol and a chalcone, were isolated. They showed a selective stimulation of Orobanche seed germination with the last two and peapolyphenol A showing a specific stimulatory activity on O. foetida. This review describes the most recent results achieved on Orobanche bio-control, mainly focusing on those regarding O. ramosa, O. crenata and O. foetida.