INDUCTION OF SYSTEMIC ACQUIRED RESISTANCE BY SALICYLIC ACID AGAINST FIRE BLIGHT IN APPLE AND PEAR

This research was conducted to evaluate and compare responses to Erwinia amylovora infection by two host species, apple (Malus  domestica Borkh.) and pear (Pyrus communis L.), activated by salicylic acid (SA). Apple rootstocks, ‘MM-111’ (tolerant) and ‘MM-106’ (susceptible), and pear cultivars, ‘Harrow Sweet’ (tolerant) and ‘Spadona’ (susceptible) were inoculated under in vitro conditions from basal parts with E. amylovora Ea273. The pathogen activity was traced by adding bromocresol green, and evaluating the pH variation in the media; measuring necrosis progression rate and counting the number of necrosed internodes in a 240 h period.
SA treatments on the in vitro shootlets were categorized by concentration (0.05, 0.1, 0.5, 1, 2, 5, 10 and 0 mg/L as control) and days of shootlets exposure to SA before infection (1, 3, 5, 7 days and 0, as control). SA did not cause similar effects on disease progress in the two tested species.
SA failed to reduce symptom progression in apple rootstocks and increased pathogenicity of bacteria.
In pear, SA presence in all treatments successfully decreased symptom progression rate in both cultivars.
Longer exposure of pear shoots to SA resulted in more effective disease control.
In both species, symptoms progression rates significantly corresponded to the pattern and severity of H2O2 generation in host tissues.
It appears that apple and pear respond differently to the SAR activation by SA. These dissimilar responses of hosts could be derived from contrasting behavior of reactive oxygen radical scavenging enzymes in the two species.

XII International Workshop on Fire Blight

Z. Ghahremani, H. Abdollahi

fire blight, systemic acquired resistance, apple, pear, salicylic acid

https://doi.org/10.17660/ActaHortic.2011.896.20