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Agriculture et alimentation

Protecting crops, protecting nature

 
 
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Microscope view of a pycnidium, a globose structure containing disseminating cells known as conidiae.

The use of particular filamentous fungi as biological agents to protect crops could provide an interesting alternative to spraying toxic chemical products. Under the European Sporefun project, researchers have used one fungus variety to control another. A demonstration project is in progress to validate the concept.

 

The Sclerotinia sclerotiorum fungus, which is widespread in Europe, causes major damage to crops. This microscopic fungus may harm nearly 400 plant species, including various plants of economic importance such as soybean, sunflower and oil seed rape. When infected, white hairy mould appears on the plant which eventually necrotises and dies.

In order to protect their harvests, farmers regularly spray fungicide over their crops. Discovering techniques which would make it possible to prevent the harm caused by this damaging agent without having recourse to toxic and costly chemical products would be beneficial, also for the environment. Surprisingly the solution could well come from another fungus, known as Coniothyrium minitans. This obligatory parasite of Sclerotinia sclerotiorum develops to the detriment of its host whose proliferation it prevents. Arthrobotrys oligospora, another fungus, neutralises a small harmful worm of the nematodes family. These fungi, which are inoffensive to the environment, could usefully replace the chemical products used to protect crops.

From chemical to biological agents

The European Sporefun project, which was completed in June 1999 after three and a half years of research, was launched to investigate this possibility. Bringing together the skills and competence of 13 partners, its objective was to study the cultivation, formulation and application of these fungi as biological control agents.

Having confirmed the antagonist effect of C. minitans and A. oligospora on their respective targets, the scientists turned their attention to the production of fungal spores. Much more resistant than mycelium, spores have the advantage of being relatively easy to conserve and formulate. On the basis of the study of the physiology of mycetes, the scientists determined the composition of an ideal culture medium for sporulation and established a spore production model using solid?state fermentation for experimental purposes. Alain Durand, of INRA in Dijon, a partner in the project, notes that this system was indispensable as many filamentous fungi do not sporulate in a liquid medium, or only poorly so.

C. minitans: a promising tool

In the case of A. oligospora, this research has not led to a culture model sufficiently efficient to serve for industrial production. However, results obtained with C. minitans have been such that an industrial pilot project could be embarked upon. Alain Durand points out that for this purpose a solid?state fermenter patented by INRA was used, which was adapted to C. minitans spore production. After 14 days of sterile fermentation - including in situ drying -, the cereal grains used as a substrate were covered and filled with fungal spores. When used, the grains are ground, suspended in water containing a wetting agent. After filtering through a bolting cloth, the spores suspension obtained is applied to the field.

Specific studies have made it possible to determine the quantity of spores required to tackle S. sclerotiorum in relation to climatic conditions and type of crop. For instance, under favourable humidity conditions 250 litres of a suspension containing 5.105 spores per millilitre (totalling 1,25.1011 spores) are on average sufficient to treat one hectare of farmland. Alain Durand explains that the pilot facility, fully computer-controlled, currently produces approximately 2,5.109 spores per gramme of dry substrate matter. As the 50 litre fermenter contains about 10 kg of dry matter, this means about 2,5.1013 spores per fermentation cycle. This dose should in theory suffice to treat 200 hectares of crops.

A success to be confirmed

Will C. minitans one day form part of the farmers' arsenal in the fight against pests? Field tests on beans and tests on lettuce grown in greenhouses have proved conclusive enough for an additional demonstration project, likewise supported by the Union, to be set up even before work under the Sporefun project had been completed. Freek Heidekamp, scientific officer at the DG for Research, notes that this was intended to demonstrate the technical and economic feasibility of C. minitans production through solid-state fermentation. At the same time, the project is intended to prove the economic and ecological advantages of applying the mycete as an agent to control S. sclerotiorum as compared with current chemical treatments. More applied, this research, carried out in collaboration with industrialists who may produce the mycete subsequently (e.g. Prophyta and Koppert BV), is intended to validate the pilot project and the formulation of spores and spore conservation techniques worked out under Sporefun. The long-term objective is of course to obtain official approval for the marketing of C. minitans spores.

   
 
Title
Sporefun (Mass production of spores of fungal antagonists by solid-state fermentation)

Reference
BIO4-CT95-0250

Programme
BIOTECH 2

Contact
G. J. de Vrije
Agrotechnological Research Institute ATO-DLO
Tel : (31) 317 475 315
E-mail : g.j.devrije@ato.wag-ur.nl

Partners
- Instituut voor Agrotechnologisch Onderzoek, Wageningen, Netherlands (coordinator)
- Plant Research International, Wageningen, Netherlands
- Universiteit Wageningen, Wageningen, Netherlands
- Nederlandse Organisatie voor Toegepast Natuurwetenschappelijk Onderzoek, Zeist and Eindhoven, Netherlands
- Koppert Biological Systems BV, Berkel en Rodenrijs, Netherlands
- National Agricultural Research Foundation, Chania, Crete (Greece)
- Prophyta Biologischer Pflanzenschutz GmbH, Malchow, Germany
- Horticulture Research International, Wellesbourne, United Kingdom
- Institut National de la Recherche Agronomique (INRA), Dijon, France
- Natural Plant Protection, Noguères, France
- Centre Technique Interprofessionnel des Oléagineux Métropolitains, Paris, France
- Prestabiol, Montpellier, France

Demonstration project
Realistic production and application of Coniothyrium minitans as a biocontrol agent

Reference
BIO4-CT98-0083

Website
http://ec.europa.eu/
research/biotech/project/
project5-en.html

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50 litre pilot reactor used for solid?state cultures under completely sterile conditions (INRA patent).

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