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More severe seasonal stresses resulting from climate change affect the survival of perennial plant species. The growth–survival trade‐off exemplified in dormant species is a key issue to understand adaptation. As the validity of this trade‐off has yet to be tested in non‐dormant species, it was assessed by exploring the intraspecific variability of strategies to face drought and frost within perennial ryegrass.Three common gardens compared 385 European perennial ryegrass populations along a latitudinal environmental gradient over 3‐years. Persistence, productivity and physiological traits were recorded under contrasting seasonal environments.Decoupling plant responses, that is, growth under favourable summers/winters and plant survival under harsh summers/winters, showed a general trade‐off between growth potential and dehydration survival. Three groups of perennial ryegrass populations were identified according to their contrasting strategies: (a) year‐round productive but stress sensitive populations from wet areas; (b) drought‐tolerant populations with low summer growth potential from drought‐prone areas and (c) frost‐tolerant populations with low winter growth potential from frost‐prone areas. Overall, the populations surviving drought best were more resource conservative, whereas populations of the other groups were more resource acquisitive. However, such overall functional patterns were less meaningful than seasonal variations of resource acquisition potentials. The predicted potential biogeographical distribution of these groups suggests shifts of areas of suitability under climate change over the next decades in Europe. Dehydration escape and dehydration tolerance through reduction of growth potential in summer may become the strategies best adapted to an increasingly large area of Europe.The large intraspecific variability of phenological adaptations within perennial ryegrass reveals that the seasonal modulation of growth potential is crucial to plant adaptation under severe chronic abiotic stresses. The global plant economics spectrum cannot account for contrasting seasonal trade‐offs, which points out the importance of integrating phenological traits as key components of plant strategies. The identification of the trade‐off between growth potential and frost or drought stress survival in this non‐dormant species provides key knowledge to understand the future regional distribution of this major species for grassland ecosystem services. A free Plain Language Summary can be found within the Supporting Information of this article. [ABSTRACT FROM AUTHOR]

The natural genetic diversity of agricultural species is an essential genetic resource for breeding programs aiming to improve their ecosystem and production services. A large natural ecotype diversity is usually available for most grassland species. This could be used to recombine natural climatic adaptations and agronomic value to create improved populations of grassland species adapted to future regional climates. However describing natural genetic resources can be long and costly. Molecular markers may provide useful information to help this task. This opportunity was investigated for Lolium perenne L., using a set of 385 accessions from the natural diversity of this species collected right across Europe and provided by genebanks of several countries. For each of these populations, genotyping provided the allele frequencies of 189,781 SNP markers. GWAS were implemented for over 30 agronomic and/or putatively adaptive traits recorded in three climatically contrasted locations (France, Belgium, Germany). Significant associations were detected for hundreds of markers despite a strong confounding effect of the genetic background; most of them pertained to phenology traits. It is likely that genetic variability in these traits has had an important contribution to environmental adaptation and ecotype differentiation. Genomic prediction models calibrated using natural diversity were found to be highly effective to describe natural populations for almost all traits as well as commercial synthetic populations for some important traits such as disease resistance, spring growth or phenological traits. These results will certainly be valuable information to help the use of natural genetic resources of other species. [ABSTRACT FROM AUTHOR]