Environmental stresses can induce a wide range of phenotypic changes in plants and impact their epigenome. DNA methylation is one of the few heritable epigenetic marks and one of its main functions is to control transposable elements (TEs) activity. In this thesis, I investigated heritable genetic and epigenetic changes induced by environmental stresses in wild strawberry (Fragaria vesca sp.). Investigating DNA methylation dynamics during stress exposure in strawberry is of interest because of the ecological and economical importance of these plants. Furthermore, findings in strawberry may be transmittable to other plants in the Rosaceae family that have more complex genomes, including apple, peach, or roses. In addition, wild strawberry is an ideal model to study long-term memory processes given its dual modes of reproduction –sexually, through seeds, and –asexually through stolons.

Using global DNA methylation and transcriptomic approaches the objectives of this project were to:

(1) Test the impact of abiotic stress on the methylome and transcriptome of F. vesca.

(2) Screening for multi-generational persistence of heat-stress-induced changes in DNA methylation patterns. As well as their potential association with gene and TE silencing and/or activation.

(3) Investigate the memory persistence differences between asexual (or vegetative) and sexual reproduction.

(4) Screening to test if epigenetic changes can contribute to stress adaptation.

In this thesis, I show that the strawberry methylome as well as transcriptome respond with a high level of flexibility to ecologically relevant stresses. Notably, the epigenome is most affected by heat-stress. Moreover, I describe that heat-stress induced DNA methylation and transcriptome changes that can be maintained for at least three un-stressed asexual generations. Finally, I describe that first sexual generation from the maternal and their clonal daughter plants showed both shared and unique stress responses, suggesting there was an acquired molecular memory resulting from heat-stress perceived by an earlier generation.

In this work, I demonstrate that stresses can induce long-lasting transmittable epigenetic changes in strawberry. Furthermore, I unravel potential differences in the transmission of epigenetic memory between sexual and asexual reproduction.