Rapid detection of Fusarium wilt in basil (Ocimum sp.) leaves by desorption electrospray ionization mass spectrometry (DESI MS) imaging

Abstract

Basil (Ocimum sp.), a medicinal herb is used fresh and/or dry in various (culinary, cosmetic and pharmaceutical) preparations. Fusarium wilt caused by the fungus Fusarium oxysporum f. sp. basilici is limiting basil cultivation in many countries. Since the leaf is the edible part in basil, new approaches are required to identify, and to prevent the spread of Fusarium pathogens. Desorption electrospray ionization mass spectrometry (DESI MS) was used for imaging thin layer chromatography (TLC)imprints of leaves of three different species of basil (Ocimum basilicum L., O. tenuiflorum L., and O. gratissimum L.), and the molecular manifestations during Fusarium contamination are recorded. DESI MS images showed the chemotaxonomic differences of basil species and the changes in metabolite ion peaks during pathogen infection. Besides easy detection of reported toxic metabolite(s) of the pathogen(s), the results include molecular images showing spatial distribution of all coexisting surfacebound metabolites in plant leaves, their fragment ions, and the transient changes in their spatial distribution during Fusarium attack under natural conditions. Demonstration of the same protocol to image seedling, young/mature leaves, basil/other related plant (Patchouli -Pogostemon cablin (Blanco)Benth.), wilt/other disease symptoms shows that prior knowledge of the metabolite profile of the plant/ pathogen is not required. This rapid detection method can be tailored to large scale screening programs for plant diseases suggesting potential implications in agriculture and quarantine requirements.

Ambient Mass Spectrometry Imaging Using Direct Liquid Extraction Techniques

“…194 Similarly, Hemalatha et al imprinted basil leaves onto TLC plates to investigate metabolites originating from the fungal infection of Fusarium . 191 Several metabolites associated with fungal infection may be distinguished by comparing ion signals from diseased plants with those from healthy plants. That study found that fusaric acid was the main characteristic toxic metabolite.…”

“…The ability to detect VLCFAs not observed in plant imprints demonstrates the advantage of direct plant tissues analysis by DESI MSI . Alternatively, prior to analysis, plant tissues may be cryo-sectioned or imprinted ,, onto a substrate, such as a TLC plate, − tape, or porous Teflon . The latter approach has been extensively used for DESI MSI of lipids and metabolites in plant tissues.…”

“…As the infection progressed, glycoalkaloids were found to decrease in abundance, suggesting that the fungi Pythium ultimum can tolerate these glycotoxins . Similarly, Hemalatha et al imprinted basil leaves onto TLC plates to investigate metabolites originating from the fungal infection of Fusarium . Several metabolites associated with fungal infection may be distinguished by comparing ion signals from diseased plants with those from healthy plants.…”

Unveiling Dynamic Changes of Chemical Constituents in Raw and Processed Fuzi With Different Steaming Time Points Using Desorption Electrospray Ionization Mass Spectrometry Imaging Combined With Metabolomics

“…The extensive application of DESI-MSI to determine natural products (primary and secondary metabolites) demonstrated its power and good practicability ( Dill et al, 2009 ; Li et al, 2012 ; Hemalatha and Pradeep, 2013 ; Hemalatha et al, 2015 ; Liao et al, 2019 ; Mohana Kumara et al, 2019 ).…”

Assessing direct analysis in real‐time mass spectrometry for the identification and serotyping of Legionella pneumophila

“…More recently, matrix assisted laser desorption ionisation time‐of‐flight MS (MALDI‐TOF‐MS) was tested for the rapid identification of Legionella and was demonstrated to be a powerful tool to achieve identification at species level, although with some difficulty at individual serogroup level (Dilger et al, 2016; Gaia et al, 2011; He et al, 2011; Kyritsi et al, 2020; Moliner et al, 2010; Pascale et al, 2020). Ambient ionisation techniques, including direct analysis in real time mass spectrometry (DART‐MS) are innovative MS techniques that require minimal or no sample preparation and allow high‐throughput differentiation of microorganisms (Braga et al, 2013; Kailasa et al, 2019; Luzzatto‐Knaan et al, 2015) at species (Cody et al, 2015; Hamid et al, 2015; Song et al, 2009) and strain levels (Cody, 2020), as well as the characterisation of their metabolites (Hemalatha et al, 2015; Jackson et al, 2008; Pierce et al, 2007; Sica et al, 2014; Tata, Perez, Campos, et al, 2015; Tata, Perez, Ore, et al, 2015; Watrous et al, 2010). Avoiding lengthy and laborious extraction procedures, ambient MS allows the nontargeted interrogation of the microbial m / z profiles and their classification based on comparison with previously established m / z signatures under ambient conditions (room temperature and atmospheric pressure).…”