Discrimination of Tilletia controversa from the T. caries/T. laevis complex by MALDI-TOF MS analysis of teliospores

The fungal genus Tilletia includes a large number of plant pathogens of Poaceae. Only a few of those cause bunt of wheat, but these species can lead to significant yield losses in crop production worldwide. Due to quarantine regulations and specific disease control using appropriate seed treatments for the different disease agents, it is of high importance to distinguish Tilletia caries and Tilletia laevis as causal agents of common bunt accurately from Tilletia controversa, the causal agent of the dwarf bunt. Several studies have shown that matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS) is a useful tool to differentiate closely related fungal species. The aim of this study was to assess whether MALDI-TOF MS analysis is able to distinguish specimens of the three closely related pathogens T. caries, T. laevis, and T. controversa and whether it may constitute an alternative method to the morphology-based identification or germination tests. Spectral data are available via ProteomeXchange with identifier PXD030401. Spectra-based hierarchical cluster analysis (HCA) and discriminant analysis of principal components (DAPC) of the obtained mass spectra showed two main clusters. One cluster included specimens of T. controversa, whereas the second cluster comprised T. laevis and T. caries specimens. Even though main spectral profiles (MSPs) for species identification are missing, MALDI-TOF MS has proven to be a useful method for distinguishing between T. controversa and the two causal agents of common bunt, using direct analysis of teliospores, but was unable to separate T. caries and T. laevis species. KEY POINTS: • MALDI-TOF MS was developed to classify Tilletia species causing bunt of wheat. • Best results were achieved when combining HCA and DAPC analysis. • The method resulted in an accuracy of 98.51% testing 67 Tilletia specimens.