In brief, this study proved that three different chitosan derivatives
induced b-1,3-glucanase, PAL and POD activities in tobacco
leaves, as local or systemic responses, on non-pathogen-inoculated
plants. Tobacco protection against P. nicotianae infection by induced
resistance was also shown. According to experimental results,
plant resistance to this pathogen could be related to the
degradation of the pathogen cell wall and to the damage caused
by defenses produced in the phenylpropanoid pathway. In addition
to the basic importance of understanding the differential activation
of defense enzymes with different types of chitosans and modes of
application, these results could also have importance in the development
of future practical means to protect tobacco plantlets
against P. nicotianae, the main soil-borne pathogen in tobacco
seedbeds.