Isolation and detailed characterisation of the first sterigmatocystin hyperproducer mould strain in Hungary

Cs Dobolyi,D Sárkány,I Bata-Vidács,A Szekeres,B Tóth,J Kukolya,O Csernus,S Kocsubé,K Inotai

doi:10.1556/066.2020.00326

Abstract

AbstractAspergillus strains were isolated from Hungarian mills in order to get information on the appearance of sterigmatocystin (ST) producing moulds, whose presence has never been demonstrated in Hungary. Fungal isolates were classified into nine morphotypes, sections Nigri, Nidulantes, Versicolores (two morphotypes), Circumdati, Flavi (two morphotypes), Clavati and Terrei by classical mycological assays. ST producing strains could be classified into section Versicolores. ST production of the isolates was assessed by liquid and solid phase growth experiments and compared to ST producing reference strains: Aspergillus pepii SzMC 22332, Aspergillus versicolor SzMC 22333, Aspergillus griseoaurantiacus SzMC 22334 and Aspergillus nidulans RDIT9.32. Four of our isolates marked as Km11, Km14, Km26 and Km31 showed ST production in liquid medium. ST production on solid phase corn grit substrate was measured after three weeks of incubation, and Km26 isolate proved to be the most prominent with a toxin concentration of 277.1 μg g−1, surpassing all reference strains. The toxin-producing ability of Km26 isolate was also tested in a field experiment, where corn was infected. By the end of the experiment, ST level of 19.56 μg kg−1 was measured in infected corn.Molecular taxonomic identification of the Km26 strain was performed using internal transcribed spacer (ITS), calmodulin and tubulin sequence analyses. Based on these studies, strain Km26 was identified as Aspergillus creber.Here we report that an ST-producing A. creber strain has appeared in Hungary, and the Km26 strain is the first known extreme ST-producing mould in this country. As a result of climate change, aflatoxin B1 producing Aspergillus flavus strains have appeared in Hungary in the last decade. As strain Km26 is the only A. creber isolate in Hungary so far, there is no sign of mass prevalence, and due to the lower temperature optimum of the species compared to A. flavus, its appearance is probably not related to climate change.

Highlights

Fungi are the major cause of spoilage in stored grain
Aspergillus strains were isolated from Hungarian mills in order to get information on the appearance of sterigmatocystin (ST) producing moulds, whose presence has never been demonstrated in Hungary
In the course of our work, Aspergillus strains were isolated from Hungarian mills

Summary

Introduction

Fungi are the major cause of spoilage in stored grain. The Food and Agriculture Association estimates that 25% of the world’s food crops are affected by mycotoxins during growth and storage. The damage of fungi is second only to that caused by insects in stored grain products. Many of the fungi cause damage to the crops themselves with little or no toxic effects on humans and animals (Scott, 1994). Mould growth can occur either before harvest or after harvest, during storage, on/in the food itself often under warm, damp, and humid conditions (Neme and Mohammed, 2017; WHO, 2018). The most frequently found mycotoxins are aflatoxin, deoxynivalenol, zearalenone, fumonisin and T-2 as far as grain crops are concerned (USDA, 2006)

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