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Differential Effects of Phenylalanine Ammonia Lyase, Cinnamyl Alcohol Dehydrogenase, and Energetic Metabolism Inhibition on Resistance of Appropriate Host and Nonhost Cereal--Rust Interactions

December 2007 , Volume 97 , Number  12
Pages  1,578 - 1,583

E. Prats, F. Martínez, M. M. Rojas-Molina, and D. Rubiales

First, third, and fourth authors: CSIC, Institute of Sustainable Agriculture, Apdo. 4084, E-14080 Córdoba, Spain; and second author: Departamento de Ingeniería Agroforestal, Universidad de Sevilla, Carretera de Utrera km1, Sevilla, Spain.

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Accepted for publication 26 July 2007.

Effects of phenylpropanoid and energetic metabolism inhibition on resistance were studied during appropriate host and nonhost cereal-rust interactions. In the appropriate barley--Puccinia hordei interaction, phenylalanine ammonia lyase (PAL) and cinnamyl alcohol dehydrogenase (CAD) inhibition reduced penetration resistance in two genotypes, suggesting a role for phenolics and lignins in resistance. Interestingly, penetration resistance of the barley genotype 17.5.16 was not affected by phenylpropanoid biosynthesis but penetration resistance was almost completely inhibited by D-mannose, which reduces the energy available in plant host cells. This suggests a parallel in the cellular basis of penetration resistance between 17.5.16 rust and mlo barleys powdery mildew interaction. Results revealed differing patterns of programmed cell death (PCD) in appropriate versus nonhost rust interactions. PAL and CAD inhibitors reduced PCD (hypersensitivity) in appropriate interactions. Conversely, they had no effect in PCD of wheat to P. hordei; whereas D-mannose dramatically reduced nonhost resistance and allowed colony establishment. The differential effects of inhibitors in the expression of the different resistances and the commonalities with the cereal-powdery mildew interaction is analyzed and discussed.

© 2007 The American Phytopathological Society