An early oxidative burst in apple rootstocks treated with DL-β-amino butyric acid (BABA) against fire blight (Erwinia amylovora)

Systemic acquired resistance (SAR) was induced by pre-treatment with the chemical inducer DL-ß- amino butyric acid against fire blight disease caused by Erwinia amylovora (Ea 7/74). The plants were inoculated with 108 cfu/ml bacterial suspension, and disease development was evaluated up to 14 days post inoculation. Although in vitro growth of bacteria was not affected by DL-ß-amino butyric acid treatment, its pre-inoculation application (500 µg/ml) significantly reduced disease severity and bacterial population. DL-ß-amino butyric acid treated plants showed significantly higher H2O2 generation, compared to untreated plants. The findings indicate that pre-treatment with the chemical inducer DL-ß- amino butyric acid activated H2O2 generation in planta more strongly when the plants were challenged with the pathogen; this may be associated with induction of plant resistance to bacterial pathogens and an effect of BABA in modulation of pathogen defence pathways.