Low-Cost Heating Modalities Allow the Detection of Biomarkers for Plant Infection Using Rapid Evaporative Ionization Mass Spectrometry (REIMS) That Are Pathogen Specific

Agricultural pathogens reduce annual crop yields by up to 40% and present a barrier to improving crop production to a level by which it will be able to support a global population of 9 billion by 2050. Current diagnostic methods are slow and lack specificity and typically rely on visual signs of infection, which appear late in the infection cycle. In this work, we explored whether the ambient ionization method rapid evaporative ionization mass spectrometry (REIMS) could be used to detect pathogen-specific biomarkers of infection against two important pathogens: the nematode Meloidogyne incognita and bacteria Pseudomonas syringae in the tomato plant (Solanum lycopersicum). Unlike previous implementations of REIMS for human clinical diagnostics, we explored the use of low-cost heating modalities in the form of a 450 nm laser and soldering iron (both below $200). After optimization, we found that the 450 nm laser provided the highest level of diagnostic classification accuracy and, importantly, could distinguish between infection causes with pathogen-specific biomarkers. This shows both the novel utility of REIMS for analysis of plant material, which would allow in situ and high-throughput analysis by the community for a broad range of plant metabolome applications, and also the potential of low-cost 450 nm lasers for use beyond this.