Induction of Phytoalexin Accumulation in Broad Bean (Vicia faba L.) Cotyledons Following Treatments with Biotic and Abiotic Elicitors

Authors: SONER SOYLU, MARK H. BENNETT, JOHN W. MANSFIELD

Abstract: Broad bean (Vicia faba) cotyledons that were inoculated artificially with fungal pathogens or exposed to various abiotic agents were analysed for phytoalexin production. Biotic elicitors, such as Botrytis cinerea and B. allii, and abiotic elicitors, such as ultraviolet (UV) radiation (254 nm) and freezing-thawing, were used to induce phytoalexin accumulation. Wyerone and other wyerone derivatives were the major phytoalexins responding in broad bean cotyledons. The quantities of wyerone within elicitor-treated tissues were examined by thin layer chromatography. The highest amount of wyerone was induced by B. cinerea (943 \mug/g fresh weight). Treatment of cotyledons with UV radiation (452 \mug/g f.wt), B. alli (325 \mug/g f.wt) and freezing-thawing (288 \mug/g f.wt) also caused considerable activation of the phytoalexin synthesis. Cell necrosis and wyerone accumulation were closely associated, and the highest concentration of wyerone was in tissue bearing brown lesions. Only very low concentrations of wyerone accumulated at sites of mechanical damage. The results indicate that the presence of both damaged and healthy tissues is necessary for phytoalexin production.

Keywords: Broad bean, Vicia faba, phytoalexin, induced resistance, abiotic elicitors

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