Background: Brown rot of stone and pome fruit is a serious fungal disease that is mainly caused by four species in
the genus Monilinia. Of these four species, Monilinia fructicola is the most devastating pathogen and of particular
concern because it undergoes sexual recombination and has recently been introduced to Europe. So far, Monilinia
diagnosis required a multiplex PCR analysis and gel electrophoresis. In contrast, intact-protein biotyping by mass
spectrometry is considerably faster and cheaper. However, it usually requires an in vitro cultivation step prior to the
MALDI analysis. It was thus attempted to establish a method for the identification of Monilinia species by MALDI biotyping
with fungal material derived directly from infected fruits; without an in vitro cultivation step.
Results: To simplify and render MALDI biotyping of fungi more reliable, an improved protocol for the preparation of
crude protein extracts and for collecting MALDI-TOF MS data for biotyping was developed. We generated reference
spectra for all four Monilinia brown rot fungi and were able to reliably identify Monilinia species based on fungal material
that was collected directly from infected fruits. This method allowed the correct, fast and economic identification
of M. fructicola and M. laxa, while M. fructigena and M. polystroma could not be distinguished reliably.
Conclusions: MALDI biotyping may be used as an economical tool for the routine diagnosis of Monilinia brown rot
fungi on infected fruits.