P-395 - Abiotic stress primes tomato immunity against Alternaria alternata

Priming describes a state of immune readiness, which is induced in plants upon memory of a prior stress exposure. Upon priming, the plant immune system responds faster and stronger to a subsequent, secondary stress. A primed state can, for example, be induced upon recognition of different biotic (e.g. MAMPs or pathogen effectors) and abiotic (e.g. salinity, drought, or cold) stresses. In this study, we aimed to investigate if a primary, mild abiotic stress application provides cross-protection against subsequent biotic stress through priming. For this purpose, young tomato plants were subjected to NaCl stress with different intensities and durations to optimise the priming conditions. After a recovery period, fungal (Alternaria alternata) and bacterial (Pseudomonas syringae) pathogens were applied. Pathogen propagation was evaluated using lesion size (A. Alternaria) or bacterial titre (P. syringae) determinations. The results suggest that exposure of young tomato plants to salt enhances their defense against A. alternata but not against P. syringae. Associated gene expression changes in the salicylic acid and jasmonic acid pathways were investigated both in response to salt and after both challenge infections. Together, the data suggests the establishment of a primed defense response in salt-treated tomato plants against A. alternata, thus potentially providing a simple and cost-effective method of enhancing plant immunity in tomato seedlings against specific pathogens.