Strengthening the antifungal efficiency of natural glycolipids for rapeseed protection in field – SHIELD

Previous work by the consortium has revealed some application and stability difficulties for these biodegradable surfactants. The project focuses on the formulation while evaluating the antifungal and defense-stimulating activity in the laboratory. The impact of the formulation on the properties related to the efficacy (wettability, retention, leaching resistance, penetration...) is evaluated. The best formulation strategies are tested in the field.

Since the beginning of the project in October 2021, the interest of using the selected glycolipids to protect rapeseed against sclerotinia has been confirmed in the laboratory and in the field on different rapeseed cultivars. The formulation trials carried out showed a good persistence of action of rhamnolipids. Work is still in progress to reinforce the efficacy of the rhamnolipids in order to obtain a competitive solution to the solutions currently used.

The SHIELD project aims to reduce the use of fungicides by at least 50% for the control of sclerotinia in rapeseed. Rhamnolipids, a natural substance used as biocontrol agent, applied by foliar spraying in the spring and combined with other integrated farming measures, could even replace the use of synthetic pesticides. The project is fully in line with the objectives of reducing pesticide use by 50% under the Ecophyto II+ PLAN.
The product developed will target a crop at the head of the crop rotation. It will be beneficial to farmers in terms of health, environmental protection and image. By reducing the residues of treatment in the productions, it will also be beneficial to consumers. It could, in the long term, be beneficial to the protection of other crops.

A part of the consortium participated in the writing of a scientific article allowing a better understanding of the impact of rhamnolipids on the translation of rapeseed proteins according to their mode of application:
Pierre, E., Marcelo, P., Croutte, A., Dauvé, M., Bouton, S., Rippa, S., & Pageau, K. (2023). Impact of Rhamnolipids (RLs), Natural Defense Elicitors, on Shoot and Root Proteomes of Brassica napus by a Tandem Mass Tags (TMTs) Labeling Approach. International Journal of Molecular Sciences, 24(3), 2390. www.mdpi.com/1422-0067/24/3/2390.
The project partnership has been presented at the American Chemical Society conference on August 21, 2022 (Chicago). Fermenting Solutions: Rhamnolipid biofungicides for natural crop protection, by Sarah Wolek (Stepan Company).

The prospect of a 50% chemical pesticide reduction by 2025 in the Ecophyto II+ plan makes urgent the identification of alternative solutions to fight fungal diseases of field crops. Numerous biocontrol solutions are effective under controlled or semi-controlled conditions. Unfortunately, the results are not always transposable to the fields. It is now critical to strengthen the efficacy of promising biocontrol solutions to bridge this gap. In particular, formulation optimization is a real lever to improve their efficacy in real-life conditions. Some bacterial glycolipids, with surfactant characteristics, show plant defense stimulating as well as antifungal properties. As biodegradable compounds, they are very promising environmentally-friendly solutions to protect crops. Data from our consortium demonstrated the interest of natural glycolipids to fight rapeseed sclerotinia which is a major issue to this culture. Indeed, this crop requires systematic fungicide sprays in the spring. This led to the development of resistant pathogen strains. Our preliminary results have shown the protective effect of non-formulated glycolipids in laboratory (TRL 4) and in field conditions against sclerotinia (TRL 5). The main objectives of the present project are to strengthen their efficiency by limiting loss mechanisms, improving their applicability and to determine the best strategy to apply them. The results will be confirmed through field trials (TRL 7) to fully exploit the potential of glycolipids in rapeseed protection against sclerotinia.Previous results revealed over time stability issues and foaming formation problems during the spray of water-diluted compounds. The project will focus on the formulation to solve these difficulties, investigating the activity of the compounds toward the pathogen and plants in laboratory conditions. The impact of formulation on the properties linked to efficacy (wetting, retention, coverage, rainfastness and penetration) will be evaluated. The best formulation strategies will be validated in field experiments.We aim to propose a final biocontrol solution to the farmers without major changes in their practices. The use of this solution would not require training, increase of their labor or impact the yield. The product cost per hectare will also be an important factor for its acceptability. By strengthening its efficacy, it could be commercialized as a competitive alternative solution to the synthetic pesticides already used to protect rapeseed. Properly formulated compounds could be commercialized as a biocontrol fungicide to substitute chemical pesticides currently used against sclerotinia. We are considering more than a 50 % reduction of fungicides. Glycolipids could replace the fungicide sprays around the optimal stage of application on rapeseed, which is the flowering time. In field trials, we will also evaluate the effect on all late rapeseed diseases. With this biocontrol solution, farmers will limit the use of conventional treatments in the event of a very strong pathogen pressure. Our results will also benefit to other crops as sclerotinia affects various fruit and vegetable crops.

The proposed consortium is balanced between two CNRS and INRAe academic laboratories and one socio-economic partner. Stepan Europe, a subsidiary of Stepan Company with expertise in the glycolipid production and in agricultural product formulation, will propose different formulation strategies providing data on stability and loss mechanisms to reinforce the glycolipid efficacy. GEC and RIBP academic laboratories will study the direct antifungal and plant protection properties of mixtures in the laboratory. This consortium of experts will be helped by service providers with skills in the evaluation of biocontrol solutions on rapeseed to carry out field trials. They will make it possible to validate the best strategy to assess the commercial use of natural glycolipids to fight sclerotinia.