• 5 years programme (2021-2025) 
• 700 715 € (243 000€ IGEPP)
• Funding: INRAE, UFS, Terres Inovia
• Coordinators: R. Delourme (INRAE IGEPP), M.H. Balesdent (BIOGER Grignon)
• Contacts:  regine.delourme@inrae.fr, anne-marie.chevre@inrae.fr

Context

Phoma or blackleg disease in oilseed rape, caused by Leptosphaeria maculans, can be controlled by two types of resistance: (i) qualitative resistance conferred by specific major genes (Rlm genes) whose effectiveness depends on the composition of avirulence alleles present in pathogen populations and (ii) quantitative resistance conferred by many low-effect loci or QTL. It has been shown that Rlm genes can be rapidly overcome but that the speed of overcoming is 'gene-dependent'. Different strategies can be used to improve the potential for durability of Rlm genes such as diversifying the type of resistance (alternating different qualitative resistance and quantitative resistance) in the varieties and rotations or combining qualitative and quantitative resistances within varieties.

Among the specific resistance genes effective in France, two genes (Rlm6 and Rlm11) have been introduced into oilseed rape from brown mustard and turnip, respectively, by the INRAE teams in Rennes and Grignon. The Rlm6 gene was introduced on the C3 chromosome with an estimated introgression size of 39 cM. The localization of the Rlm11 gene is in progress. The AvrLm6 gene was cloned and the frequency of the virulence allele was evaluated at less than 1% ten years ago in French L. maculans populations. The AvrLm11 gene was also cloned and is carried by a 'dispensable' chromosome whose frequency of absence has been estimated to an average of 3.5%. No change in this frequency has been noted in 10 years (between 2000 and 2010) whereas a high percentage of dispensable chromosome loss at each meiosis (estimated at around 5%) should have led to a decrease in the frequency of the AvrLm11 allele in populations. This stability, in the absence of Rlm11 pressure, suggests a significant fitness cost linked to the loss of the dispensable chromosome. The evolution of this frequency under selection pressure by Rlm11 is not known.

Objectives

The ClubPhoma project is an innovative project that associates the release of these two Rlm genes (Rlm6 and Rlm11) to UFS members to the set-up of a collaborative research space to share experiences and results between federated public and private communities all along the pre-breeding process, around the following objectives:

• Developing tools (molecular markers) for breeding and developing new sources of resistance;
• Organizing the collective deployment and monitoring of resistance to anticipate and understand the evolution of the L. maculans population through the set-up of a monitoring network;
• Supporting the construction and emergence of a collective strategy for the sustainable management of resistance genes by getting the stakeholders involved in this sustainable management to work together and by developing arenas and adapted management tools.

Partners

R. Delourme, A.M. Chèvre, M. Rousseau-Gueutin (DEBI Team, IGEPP Le Rheu); M.H. Balesdent, J. Soyer, V. Laval (BIOGER Grignon); L. Bousset (DEMECOL Team, IGEPP Le Rheu) ; F. Coleno (SADAPT Paris Saclay) ; X. Pinochet (Terres Inovia) ; UFS (11 seed companies: BASF France, Bayer Seeds, Lidea, Corteva Pioneer génétique, DSV France, KWS Momont Recherche, Limagrain Europe, MAS Seeds, NPZ Lembke, RAGT Semences R2n and Syngenta)e web.