PROTECTIVE EFFECT OF HRP MUTANTS OF ERWINIA AMYLOVORA AGAINST A VIRULENT STRAIN OF THE PATHOGEN: EXPRESSION IN SEVERAL BIOLOGICAL SYSTEMS AND PRELIMINARY MECHANISTICS STUDIES

The protective effect of two Hrp mutants (a regulatory and a secretory mutant) was studied.
Unwounded apple seedlings and apple blossoms were used, in the glasshouse.
These two systems showed that highest level of protection was obtained with mutant in regulation gene when both bacteria in challenge were inoculated simultaneously.
A system of co-culture of apple cell suspension with avirulent and virulent bacteria was also used.
Under these conditions, all Hrp mutants tested prevented cell death with no difference between the location of the mutation.
The dynamic of bacterial growth in planta indicated that the protection was closely related to the inhibition of the multiplication of the virulent strain in the host tissues.
The activation of two enzymes, phenylalanine ammonia lyase and guaiacol peroxidase was observed with the regulatory mutant and suggested that this mutant could induce a host defense response.

VIII International Workshop on Fire Blight

M. Faize, M. Tharaud, M.N. Brisset, J.P. Paulin

hrp mutants, plant defense response, apple, Erwinia amylovora

https://doi.org/10.17660/ActaHortic.1999.489.113