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Effects of Phenylpropanoid and Energetic Metabolism Inhibition on Faba Bean Resistance Mechanisms to Rust

First author: ETSIAM, Departamento de Genética, Universidad de Córdoba, Apdo 3048, E-14080, Córdoba, Spain; second and third authors: CSIC, Instituto de Agricultura Sostenible. Apdo. 4084, E-14080 Córdoba, Spain; and fourth author: CIFA-IFAPA, área de Mejora y Biotecnología, Apdo. 3092, E-14080 Córdoba, Spain

Effects on penetration and hypersensitive resistance of the cinnamyl acid dehydrogenase (CAD) suicide inhibitor ([(2-hydroxyphenyl) amino] sulphinyl) acetic acid, 1.1 dimethyl ester, which suppresses phenylpro-panoid biosynthesis, and of D-mannose, which sequesters phosphate and reduces energy available in host cells, were studied in faba bean (Vicia faba) genotypes with differing resistance mechanisms to faba bean rust (Uromyces viciae-fabae). Inhibition of CAD reduced penetration resistance in lines 2N-34, 2N-52, V-1271, and V-1272, revealing an important role for phenylpropanoid biosynthesis in the resistance of these lines. Inhibition of CAD also inhibited hypersensitive cell death in these lines. D-mannose had little or no effect on resistance. By contrast, CAD inhibition did not affect penetration resistance of line BPL-261, which has a high degree of penetration resistance not associated with hypersensitive cell death. In BPL-261, D-mannose inhibited penetration resistance. The parallelism between the faba bean genotype responses to rust observed here and the response of barley genotypes with differing resistance mechanisms to powdery mildew after similar inhibitor treatments is analyzed and discussed.

Additional keywords: hypersensitive cell death response, lignin.