Liebig review: The role of mineral nutrients in the development of Pseudomonas syringae diseases—Lessons learned and implications for disease control in woody plants

Background: The plant pathogen Pseudomonas syringae (Ps) causes diseases in a broad range of hosts including important cash crops from several climate zones. In particular for woody crops, effective and environmentally friendly disease control strategies are not available. Although there is increasing evidence of a link between plant nutritional status and disease susceptibility, optimization of plant nutrition is often neglected in efforts to control Ps diseases. This review brings current knowledge on this topic together with the aim of facilitating the development of treatment recommendations in specific contexts. Literature review: The article consists of three parts. First, we compiled data on the impact of mineral nutrients on Ps disease severity in woody and herbaceous species. Next, we discuss how nutrients may be related to plant defense and/or Ps virulence. Last, we consider these findings in the context of woody hosts and give suggestions for future research. Conclusions: We encourage a research focus on typical nutrient imbalances (deficiencies and surpluses) in specific orchard regions; testing the role of foliar fertilizers in spring (the period of highest infection risk); analyses of the interaction between nutrient supply and the microbiome in the phyllosphere; investigating the interaction between nutrient supply and other control measures, and the impact of nutrient supply on Ps diseases in the presence of other stress factors.