Plant Protect. Sci., 2002, 38(10):S139-S140 | DOI: 10.17221/10339-PPS

Molecular defense responses of apple genotypes in compatible and incompatible interactions with Erwinia amylovoraOriginal Paper

M.N. Brisset, J.S. Venisse, J.P. Paulin

¹ UMR Pathologie Végétale INRA/INH/UA and

² Unité d'Amélioration des Plantes INRA, Centre d'Angers, 49071 Beaucouzé Cedex, France Tel.: +33 2 4122 5700, Fax: +33 2 4122 5705, E-mail: brisset@angers.inra.fr

Erwinia amylovora is the causal agent of fire blight, a bacterial disease of apple and pear. Pathogenicity determinants of the bacteria are identified (hrp-dsp cluster, capsule, siderophore) but molecular mechanisms leading to susceptibility or resistance of the plant are not yet understood. To address this question, we challenged two genotypes of apple, known for their contrasting susceptibility to fire blight, with a wild-type strain of E. amylovora (Ea wt), an avirulent hrp mutant of this bacteria (Ea hrp) or a wild-type strain of the incompatible pathogen Pseudomonas syringae pv. tabaci (Pst wt). Mechanisms usually related to resistance responses were investigated i.e. oxidative stress, accumulation of PR-proteins and induction of genes encoding various enzymes of the phenylpropanoid pathway. Results showed two kinds of responses (i) some mechanisms were elicited in both susceptible and resistant genotypes by Ea wt and Pst wt with similar kinetics and not induced by Ea hrp, (ii) others were specifically repressed by Ea wt in its susceptible host, when induced by Pst wt and Ea hrp. These results suggest several hypothesis about the cross-talk between E. amylovora and its host plants.

Keywords: Erwinia amylovora; defense; compatibility; incompatibility; hrp mutant

Published: June 30, 2002  Show citation