beta-Aminobutyric Acid-induced Resistance in Cucumber against Biotrophic and Necrotrophic Pathogens

The non-protein amino acid beta-aminobutyric acid (BABA) protects plants against a wide range of pathogens. Protection of cucumber plants by BABA depends on the potentiation of pathogen specific defence responses. To contribute to the analyses of the mode of action of BABA, we established a protocol for a fast and reproducible leaf disc assay to evaluate the effect of this chemical compound on cucumbers infected with either the biotrophic downy mildew fungus Pseudoperonospora cubensis, or the necrotrophic microbial pathogen Colletotrichum lagenarium. Accumulation of callose could be found in interactions with both pathogens after BABA-treatment. Furthermore, a localized rapid cell death and the production of reactive oxygen intermediates were detected after downy mildew attack. In contrast to this, degenerated primary hyphae were found in BABA induced tissue after inoculation with C. lagenarium.