Black Aspergilli and fumonisin contamination in onions purchased in Hungary

Abstract

Black mold rot caused by black Aspergilli is an important post-harvest disease of onion worldwide. Usually Aspergillus niger is cited as the causative agent based on morphological criteria. In this study, the mycobiota and fumonisin contamination of mouldy onion bulbs purchased in Hungary were examined. All except one of the examined mouldy samples were found to be contaminated with black Aspergilli, which could be isolated both from the outer dry and the inner fleshy scales of onion bulbs. Species assignment of the isolates was carried out using sequence analysis of part of the calmodulin gene. Sequence data revealed that all 35 black Aspergilli isolated from onions belong to the Aspergillus awamori species. The range of fumonisin isomers present in the onion samples was also examined using reversed-phase high-performance liquid chromatography/electrospray ionization -ion trap mass spectrometry.Two of the examined onion samples were found to be contaminated with fumonisins at a rate of about 0.3 mg kg -1 . This is the first report on fumonisin contamination of onion bulbs. The fumonisin isomers observed include fumonisins B 2-4 , 3-epi-FB 4 , iso-FB 1 (FB 6 ) and an iso-FB 2,3 form. The range of fumonisin isomers detected in the onion bulbs indicates that probably A. awamori is responsible both for mold rot and fumonisin contamination of onions in Hungary.

Aspergillus Luchuensis, an Industrially Important Black Aspergillus in East Asia

“…Isolates of A. welwitschiae have been reported on various substrates as mycotoxin producers or plant pathogens including grapes [15], onions as causative agents of black mold rot and fumonisin contamination [33] and Welwitschia mirabilis seeds causing seedling rot (van Diepeningen et al unpublished data). In addition, this species was also identified in various otomycosis cases both in Iran and Hungary [34], [35].…”

“…Although the name A. awamori was used taxonomically correctly by Perrone et al [15], this currently used name is misleading, as this species is rarely identified in awamori fermentation processes, where mostly A. niger and A. luchuensis could be isolated [11]. It should also be mentioned that isolates of A. awamori sensu Perrone are able to produce ochratoxins and/or fumonisins [15]; [33], making the application of the name of an oriental fermentation process as the basis of the name of this fungus is inadequate.…”

Exposure, Occurrence, and Chemistry of Fumonisins and their Cryptic Derivatives

“…Varga et al. () detected FB2, FB3, FB4, and FB6 at about 325 to 330 μg/kg in 29% of the onions exhibiting signs of rot disease, but not in heathy controls ( n = 7). Toxin contamination was attributed to Aspergillus awamori (Varga et al., ).…”

First report of Penicillium georgiense as a fungal pathogen of onion (Allium cepa L.)

“…Further, we observed other minor Penicillium spp., among which a specific species (identified as P. georgiense in this study) (4.3% of total fungi isolated) was frequently (70% of total P. georgiense isolates) isolated along with A. awamori. A. awamori was reported as a fungal pathogen on onion bulbs Varga et al, 2012) and has been difficult to differentiate from Aspergillus niger, which is recognized as the fungal pathogen causing black mold on onion bulbs (Pozzo-Ardizzi et al, 2012;Schwartz and Mohan, 2008). In our previous study , P. georgiense (which was proven to be pathogenic against onion bulbs in this study) was frequently co-isolated with A. awamori from onion bulbs; thus, it may be possible that these two fungal species (P. georgiense and A. awamori or A. niger) act synergistically to cause postharvest diseases in onion.…”