Identification of Alternaria, Aspergillus, Fusarium and Penicillium spp. on Onion Plant (Allium cepa L.) Growing in Hatay, Amasya and Tokat Provinces Using MALDI-TOF Mass Spectrometry

Plant fungal disease pathogens cause significant yield and quality losses in onion growing areas. In addition to yield losses, they cause negative effects that reduce the quality and export potential of the product, resulting in significant economic losses during harvest, post-harvest, processing and marketing stages. In recent years, Matrix-Assisted Laser Desorption/Ionization-Time of Flight Mass Spectrometry (MALDI-TOF MS) has emerged as a rapid, cost-effective, reproducible, and powerful technique for identifying microorganisms, and its impact on microbiological diagnosis has transformed workflow in equipped laboratories. In this study, proteomic analyzes were performed on Alternaria, Aspergillus, Fusarium and Penicillium species isolated from onion growing areas in Hatay, Amasya, and Tokat provinces. After extraction of mycelium from single spore cultures of the isolates with ethanol-formic acid, the spectra of the individual fungal isolates were determined using the Flex control software program. These spectra were compared with Maldi Biotyper Real-Time Classification (RTC) and identification was performed. Of 519 different fungal isolates, 435 representative fungal isolates (83.8%)  were identified by MALDI TOF MS. Eighty-four fungal isolates could not be identified because they were not in a satisfactory range of purity and identification. Of the 435 isolates, 269 (61.8%) were identified as Fusarium spp., 80 isolates (18.4%) were identified as Alternaria spp., 60 isolates (13.8%) as Aspergillus spp., and 26 isolates (6.0%) as Penicillium spp. Among the fungal isolates, 72.5% of the Fusarium isolates, 78.8% of the Alternaria isolates, 90.0% of the Aspergillus isolates and 84.6% of the Penicillium isolates were identified as “highly probable” species with score values between 2.000-3.000 (green color). These species are Alternaria alternata, Alternaria infectoria, Aspergillus flavus, Aspergillus niger, Fusarium culmorum, Fusarium moniliforme, Fusarium oxysporum, Fusarium proliferatum, Fusarium solani, Fusarium verticillioides, Penicillium commune and Penicillium glabrum. The results clearly demonstrate that MALDI TOF MS biotyping may be used as a highly reliable and economical diagnostic method for routine diagnosis of diseases caused by Alternaria, Aspergillus, Fusarium and Penicillium species.