Stuttgart, Germany
July 2009

Verticillium longisporum is a vascular fungal pathogen presently threatening oilseed rape production in Europe. Systemic spread of susceptible and resistant genotypes after dip-inoculation of the roots followed by quantitative polymerase chain reaction revealed similarities only in the initial stages of root penetration and colonization of the hypocotyl, while a substantial invasion of the shoot was only recorded in susc eptible cultivar.

It is concluded that the type of resistance does not prevent the plant base from being invaded as it is internally expressed well after root penetration and colonization of the plant base. Histochemical studies revealed the build-up of vascular occlusions and the reinforcement of tracheary elements through the deposition of cell wall-bound phenolics and lignin. Furthermore, the accumulation of soluble phenolics was observed. Although these responses were found in vascular tissues of both genotypes, they occurred with a significantly higher intensity in the resistant genotype and corresponded with the disease phenotype. In the resistant genotype phenols were differentially expressed in a time-dependent manner with preformed soluble and cell wall-bound phenolics at earlier time points and de novo formation of lignin and lignin-like polymers at later stages of infection. This is the first study identifying a crucial role of phenol metabolism in internal defense of B. napus against V. longisporum and locating the crucial defense responses in the plant hypocotyl (Eynck and coworkers (2009), published in Phytopathology 99 (7), 802-811).

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Published: July 15, 2009