Resistance induction in plants by a brassinosteroid-containing extract of Lychnis viscaria L.

Resistance inducing effects of an extract of Lychnis viscaria L. seeds, con taining different brassinosteroids (BR), were investigated. Application of aqueous solutions in concentrations from 0.5 to 10 mg/l (dry wt. of extract ) resulted in an enhanced resistance of tobacco, cucumber and tomato to vir al and fungal pathogens of up to 36% compared with water-treated control pl ants. No direct anti-fungal effects in mycelium growth assays with Phytopht hora infestans could be observed. After treatment and inoculation with powd ery mildew a stimulation of different PR-proteins (ca. + 20% for peroxidase , + 30% for chitinase and up to + 68% for beta-1,3-glucanase) in cucumber w as found. A chitinase in gel-electrophoresisassay showed a stronger inducti on of a distinct isoform under the same conditions. Time course of peroxidase induction and changes of apoplastic protein patte rns revealed by SDS-PAGE indicated an earlier triggering of defence respons es after plant-extract treatment and pathogen attack, probably being respon sible for the increased resistance. Involvement of the brassinosteroids in the plant extract is discussed to elicit or mediate the activation of defen ce-mechanisms.