EasyHybrids

• 3,5 years program (2020-2023)
• 196 000€ (fonctionnement) ; CDD Technicien 10 mois
• Founding: Institut Carnot (Plant2Pro)
• Coordinators: F. Borges (INRAE IJPB Versailles) et O. Coriton (INRAE IGEPP)
• Contact:  olivier.coriton@inrae.fr

Context

EasyHybrids proposes to evaluate a novel, cheap strategy to overcome the "triploid block", a major obstacle for the production of triploid plants, and for the transfer of exotic alleles into elite cultivars.
Previous studies in Arabidopsis have shown that is possible to overcome triploid seed lethality by reducing the level of DNA methylation and small RNAs in diploid pollen (Schatlowski et al., 2014; Martinez et al., 2018; Borges et al., 2018; Erdmann et al., 2017). Such epigenetic modifications may be rapidly and easily induced by treating plants with the chemical inhibitor of DNA methylation 5-azacytidine (5-Aza) during early plant development. Interestingly, F. Borges (INRAE IJBP, Versailles) recently observed that such a transient treatment also allows suppression the triploid block in Arabidopsis, Capsella and tomato (unpublished data). Epigenetic variation induced by 5-Aza may be restored to normal in the subsequent generations, thus preventing major impacts on plant development and genome stability. For these different reasons, we are convinced that this strategy may be a powerful tool in breeding programs that require the production of interploidy and interspecific hybrids.

Objectives

EasyHybrids aims at demonstrating the feasibility of using a transient 5-Aza treatment to:

1. Bypass interploidy hybridization barriers that prevent triploid seed production in Miscanthus. Main bottlenecks for the adoption of this crop are the inefficient and costly vegetative propagation of the only cultivated variety, the sterile interspecific hybrid M x giganteus, and the potential invasiveness of other seed-propagated varieties. In this context, the goal is to produce a new generation of sterile hybrid Miscanthus varieties propagated by triploid seeds, which will be obtained from crossing diploid with tetraploid parents. Such crosses are highly inefficient due to the triploid block, and overcoming this obstacle is expected to open the way to a large-scale production and commercialization of seed-propagated but sterile mMiscanthus.
2. Bypass interspecific and intergeneric crosses for breeding of Brassica of high agronomical value. Crosses between Brassica napus and its diploid progenitors B. rapa and B. oleracea, and even with more distantly related species such as Sinapis alba, are often performed for introduction of resistance alleles to biotic and abiotic stresses. However, the efficiency of such hybridizations is very low, requires sophisticated techniques for embryo rescue at best, or is simply not feasible. Based on our preliminary results in Capsella and tomato, we expect that reducing DNA methylation in B. napus pollen will also allow the production of an increased number of intergeneric hybrid seeds.

In addition, and to further improve the experimental approach, we will 3) investigate the mechanism by which epigenetic variation induced by 5-Aza treatment suppresses the triploid block in Arabidopsis. We will profile genome-wide DNA methylation of 5-Aza-treated plants in different developmental stages, and the main goal is to quantify the levels of DNA methylation transmitted to the male germline, and how that correlates with the triploid block response.

Partners

• Partner 1 : F. Borges (INRAE IJPB Versailles)
• Partner 2 : O. Coriton (INRAE IGEPP Le Rheu)