The use of synthetic analogues of natural inhibitors as a sustainable strategy to reduce trichothecene contamination of cereals

ISMAEL MALBRÁN

Ciudad Autónoma de Buenos Aires

Congreso; Colloquium of the Alexander von Humboldt Foundation; 2018

Alexander von Humboldt Foundation

The cereal pathogen Fusarium graminearum is the predominant incitant of Fusarium head blight (FHB) worldwide. The disease reduces cereal yield and grain quality and contaminates the grain with mycotoxins, secondary fungal metabolites toxic to humans and animals. The type B trichothecenes deoxinivalenol (DON), their acetylated derivatives (3-ADON and 15-ADON), and nivalenol (NIV) are the most common mycotoxins produced by F. graminearum. Trichothecenes induce apoptosis and play an important role in the aggressiveness towards plant hosts. Strictly enforced limits to the concentrations of trichothecenes permitted in unprocessed grain and processed foods and animal feed have been stablished both in the USA and in Europe.Fungicides, resistant cultivars, cultural practices, and biological control are among the methods used to manage FHB. However, none of them is fully effective at reducing the severity of the disease. Furthermore, prolonged use of fungicides that share the same action mechanism (e.g., sterol biosynthesis inhibitors) induces a selective pressure on the pathogenic fungal populations, enabling the selection of resistance, and may increase mycotoxin contamination of the grain when fungicides that differ in activity against different FHB pathogens are applied or doses lower than the recommended are used. Therefore, there is an urgent need to develop new compounds able to counteract the pathogenic and mycotoxigenic potential of F. graminearum.Our project, which started on August 2017 and involves researchers from the Italian Consiglio Nazionale di Ricerca (CNR) and the Argentinian Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), aims at identifying, designing, formulating, and characterizing a series of molecules based on the structure of natural/natural-like inhibitors, able to counteract the pathogenic and mycotoxigenic potential of natural populations of Fusarium.A preliminary in silico study based on the best interaction between the enzymes involved in the biosynthesis of trichothecenes and a collection of molecules was developed by the CNR counterpart of the project. Once a group of compounds, mainly phenols and polyphenols, with potential for trichothecene inhibition were selected, we developed in vitro tests aimed at evaluating their efficacy. In vivo inhibition of trichothecene production is being evaluated on field tests. To do so, a headspace solid-phase microextraction-capillary gas chromatography and mass spectrometry (HS-SPME-CGC-MS) technique, developed by the CONICET counterpart of the project, is being used to detect the production of trichodiene, the first common precursor of trichothecenes, in wheat spikes inoculated with F. graminearum and treated with the selected inhibitors.