Effect of Fungal and Plant Metabolites on Broomrapes (Orobanche and Phelipanche spp.) Seed Germination and Radicle Growth

Orobanche and Phelipanche species (the broomrapes) are root parasitic plants, some of which cause heavy yield losses on important crops. The development of herbicides based on natural metabolites from microbial and plant origin, targeting early stages on parasitic plant development, might contribute to the reduction of broomrape seed bank in agricultural soils. Therefore, the effect of metabolites belonging to different classes of natural compounds on broomrape seed germination and radicle development was assayed in vitro. Among the metabolites tested, epi-sphaeropsidone, cyclopaldic acid, and those belonging to the sesquiterpene class induced broomrape germination in a species-specific manner. epi-Epoformin, sphaeropsidin A, and cytochalasans inhibited germination of GR24-treated broomrape seeds. The growth of broomrape radicle was strongly inhibited by sphaeropsidin A and compounds belonging to cyclohexene epoxide and cytochalasan classes. Broomrape radicles treated with epi-sphaeropsidone developed a layer of papillae while radicles treated with cytochalasans or with sphaeropsidin A turned necrotic. These findings allow new lead natural herbicides for the management of parasitic weeds to be identified.
The research was carried out in part in the frame of Programme STAR, financially supported by UniNA and Compagnia di San Paolo, and in part in the frame of project FP7-ARIMNetMEDILEG. This work was carried out within the COST ACTION FA1206 Strigolactones: biological roles and applications. Monica Fernandez-Aparicio has received support from the ́ European Union, in the framework of the Marie-Curie FP7 COFUND People Programme, through the award of an AgreenSkills’ fellowship (under grant agreement n° PCOFUNDGA-2010−267196). A. E. is associated with the Istituto di Chimica Biomolecolare del CNR, Pozzuoli, Italy.