Bridging landscape genomics and quantitative genetics for a regional adaptation of European grasslands to climate change

Summary
In the next decades, grasslands as important ecosystems and basis of dairy and meat production are likely to experience damages and subsequent production losses due to changing climate. Recent events (e.g. severe drought in Western Europe in 2003) highlighted an insufficient capacity in local populations of grassland species to cope with unusual climatic events. However, most grassland species show a large ecotypic diversity over wide environmental ranges. We consider that this large ecotypic diversity could be used to recombine natural climatic adaptations and value for services to create improved populations of grassland species adapted to the foreseen future regional climates.

To implement this strategy, it is necessary to have extended knowledge of the adaptive diversity existing in grassland species. With this aim, we intend to use an innovative methodological frame (landscape genomics) to screen the natural diversity of a grassland species (perennial ryegrass) in order to discover genetic variability involved in environmental adaptation, and more specifically in climatic adaptation. The landscape genomics approach is based on the combined use of methods correlating genomic polymorphisms and environmental variations at sites of origin of genotypes and of tests of signature of selection.

To implement this frame, we will use a genotyping method based on massively parallel sequencing technology applied to 550 populations of perennial ryegrass sampled across the whole area of primary expansion of this species (Europe, Northern Africa and Near East). These populations will be taken out from genebanks of plant breeding institutes or collected in situ across Europe.Our genotyping protocol is expected to deliver several tens thousands of polymorphisms sites along perennial ryegrass genome. We will furthermore phenotype these populations in fields and in controlled environment to record agronomic and eco-physiological traits. Association models between genomic polymorphisms and environmental variations will be used to map the spatial distribution of genomic markers linked to adaptive diversity in present climatic conditions and to foresee possible shifts in the spatial range fitting these markers in the context of several climate change scenarios based on the four Representative Concentration Pathways of IPCC AR5.

Based on these results, we will define allelic profiles of perennial ryegrass expected to provide climatic adaptation at regional scale over Europe under the future climatic conditions foreseen by climate models. We will consider combining climatic adaptation and value for services by genetic recombination. We will finally design a number of genetic pools mixing different natural populations. These genetic pools will be the basis to initiate breeding programmes aiming to deliver improved populations adapted to future regional climates. These improved populations will enable to restore grasslands degraded by future climatic disruptions.