Species identification of Aspergillus section Flavi isolates from Portuguese almonds using phenotypic, including MALDI-TOF ICMS, and molecular approaches
Section Flavi is one of the most significant Sections in the genus Aspergillus. Taxonomy of this section currently depends on multivariate approaches, entailing phenotypic and molecular traits. This work aimed to identify isolates from section Flavi by combining various classic phenotypic and genotypic methods as well as the novel approach based on spectral analysis by MALDI-TOF ICMS, and to evaluate the discriminatory power of the various approaches in species identification.
Methods and Results Aspergillus section Flavi isolates obtained from Portuguese almonds were characterised in terms of macro- and micromorphology, mycotoxin pattern, calmodulin gene sequence and MALDI-TOF protein fingerprint spectra. For each approach, dendrograms were created and results were compared. All data sets divided the isolates into 3 groups, corresponding to taxa closely related to A. flavus, A. parasiticus and A. tamarii. In the A. flavus clade, molecular and spectral analyses were not able to resolve between aflatoxigenic and non-aflatoxigenic isolates. In the A. parasiticus cluster, two well-resolved clades corresponded to unidentified taxa, corresponding to those isolates with mycotoxin profile different from that expected for A. parasiticus.
Conclusions Good agreement was obtained between methods on species level identification. The incongruences detected in classic phenotypic analysis were generally well resolved with the molecular and/or spectral analyses. MALDI–TOF ICMS demonstrated to be sensitive and accurate in species discrimination.
Significance and Impact of Study MALDI–TOF ICMS when compared with other identification methods currently used can be regarded as an objective and fast analytical methodology suitable for applications which have particular needs in high-throughput and highly accurate identification.
