Innovative strategies with sustainable fungicides of new composition towards mycotoxin Fusarium control in cereals.

Project leaders

Giovannamaria Delogu, Ismael Malbrán

Agreement

ARGENTINA - CONICET - Consejo Nacional de Investigaciones Científicas y Técnicas

Call

CNR/CONICET biennio 2017-2018 2017-2018

Department

Chemical sciences and materials technology

Thematic area

Chemical sciences and materials technology

Status of the project

New

Research proposal

Several Fusarium species, including the cereal pathogens F. culmorum and F. graminearum, are the predominant incitants of Fusarium head blight (FHB) and crown and foot rot (CFR) worldwide. Yield and quality losses are caused by FHB, which develops from infection that occurs at anthesis and spreads until grain harvest, causing the grain to be contaminated with mycotoxins. These include trichothecenes, sesquiterpene epoxides able to inhibit eukaryotic protein synthesis and to cause toxicosis on humans and animals consuming contaminated food or feed (Sudakin 2003).
The type B trichothecenes deoxinivalenol (DON), their acetylated derivatives (3-ADON and 15-ADON), and nivalenol (NIV), produced mainly by F. graminearum and F. culmorum, are predominant both in Europe and Argentina. They induce apoptosis and, in some cases, play an important role in the aggressiveness towards plant hosts. In both the USA and Europe, there are strictly enforced limits to the concentrations of DON permitted in unprocessed grain as well as in processed foods and animal feed (European Commission Regulations Nos. 856/2005 and 1126/2007; advised by the US Food and Drug Administration; Jansen et al., 2005).
Fungicides, resistant cultivars, burial of infested debris, and biological control methods can all potentially decrease severity of FHB. Although the application of fungicides is the most common control method, it is not always effective. Prolonged use of different fungicides sharing the same mode of action (e.g., sterol biosynthesis inhibitors) induces a selective pressure on the pathogenic fungal populations, enabling the selection of resistance. Furthermore, increases in mycotoxins can occur when fungicides that differ in activity against different FHB pathogens are applied or doses lower than the recommended are used (Simpson et al 2001). Consequently, there is an urgent need to develop inhibitory compounds of new generation, able to counteract the pathogenic and mycotoxigenic potential of natural populations of Fusarium or to stimulate or strengthen natural resistance responses by the host plant.
The genes that control most of the trichothecenes biosynthesis were characterized and found to be located within in a single core cluster, named TRI. TRI5 encodes the enzyme trichodiene synthase which catalyzes the synthesis of trichodiene, the first common precursor of trichothecenes. TRI5 X-ray crystal structure provides useful insights on the possibility to use external ligands to interfere with the mycotoxin production. It shall provide an additional tool to discover new molecules with potential as fungicides or as trichothecene inhibitors. In this scenario, the search for alternative management approaches, including the development of natural fungicides or inhibitors of mycotoxin biosynthesis, appears particularly promising.
Natural inhibitory compounds and fungicides are mostly extracted from plants and are involved in host resistance response. The mechanisms by which these compounds interfere with the biosynthesis of trichothecenes are not yet completely understood, and numerous hypotheses have been proposed, including transcriptional control of TRI genes, modification of the fungal membrane permeability, inhibition of fungal enzymes, and alleviation of oxidative stress that is assumed to activate the biosynthesis of mycotoxins.
The project 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, or capable to stimulating natural resistance responses by the host plant. A specific and powerful inhibitory activity was demonstrated by cell wall-bound oligogalacturonides and by phenolic compounds. To increase the activity and bioavailability of the most effective molecules, these will be delivered by sustainable and non-phytotoxic carriers.
The activity will be supported by a preliminary in silico study based on the best interaction between trichodiene synthase and a collection of molecules, mainly phenols and polyphenols. This expertise is present in the CNR UNIT as well as the study and synthesis of natural occurring phenols and polyphenols. In vivo testing will be carried out with selected molecules in order to evaluate their efficacy in reducing FHB symptoms in wheat as well as trichodiene accumulation in the spikes, which will be evaluated using a straightforward method developed by the CONICET UNIT. The location of the CNR and CONICET UNITs on different hemispheres would allow carrying on two field tests per year, hence duplicating the amount of data generated.
Over the last 10 years the integrated CNR UNIT (organic synthesis chemists and one phytopathologist) and CONICET UNIT (phytopathologists, biochemist, molecular biologists) have established a complex network of scientific cooperation with a number of foreign laboratories in Europe and in Argentina, respectively (see CNR and CONICET components CVs), that will be directly or indirectly involved in the activities foreseen in the present project. Recently, the young researcher responsible of the CONICET UNIT spent two years at the University of Sassari joining a co-operation with the components of the CNR UNIT in the evaluation of natural and natural-like compounds with fungicide and inhibition activity towards FHB pathogens.
This project would offer the possibility to build up a long lasting collaboration and competence transfer between the two research units which will enhance their mutual capacities in the research on FHB pathogens. This will be especially valuable for the CONICET UNIT, which is mainly composed by young researchers and grant holders. Implementation and reinforcement of a Fusarium intercontinental community network will create, together with the European collaborations still present, a broad excellence basis in future projects.

Research goals

1. In silico study of the interaction between trichodiene synthase and inhibitory molecules, mainly phenols and polyphenols.
2. Selection of natural potential inhibitors of TRI5.
3. Designing by sustainable synthetic methodologies of analogues of the natural occurring compounds selected at point 2 (natural-like) with improved interaction with TRI5.
4. In vitro evaluation of the effect of inhibitory molecules on fungal growth
5. Evaluation in vitro and in vivo of the effect of inhibitory molecules on the biosynthesis of type B trichothecenes and trichodiene by spectroscopic analysis (LC-MS/MS and HS-SPME CGC-MS).
6. In vitro and in vivo evaluation of the fungicidal activity of selected natural and natural-like molecules.
7. In vivo evaluation of the infection process in lines of wheat with different resistance towards FHB, previously treated and non-treated with inhibitory molecules.
8. In vivo evaluation of sustainable carriers to improve bioavailability of molecules with fungicide and/or inhibitory activities.
9. In vivo evaluation of mixture of molecules with fungicide and inhibitory activities with suitable no-phytotoxic carriers (synergist effect).
10. Dissemination of results and training activity to young researchers and students.
11. Integrating CNR and CONICET units' expertise on innovative strategies to control FHB in wheat and maize. Researcher visits will be devoted to sharing expertises in improving the project targets.

Last update: 20/04/2024