Transgenerational effects of mycorrhiza are stronger in sexual than in clonal offspring of <i>Fragaria vesca</i> and are partly adaptive

Abstract Whilst transgenerational effects (TGE) of abiotic conditions are becoming generally accepted in plants, those of biotic interactions remain largely unexplored. We therefore investigated the influence of TGE due to arbuscular mycorrhiza, the most widespread mutualistic interaction of plants with microorganisms, on clonal and sexual offspring of Fragaria vesca . We hypothesized that the ecological and evolutionary significance of TGE will vary between clonal and sexual offspring based on mycorrhizal status and phosphorus (P) availability experienced by the parent. In a two‐generation greenhouse experiment, parental plants were exposed to full‐factorial combinations of mycorrhizal status and high or low P availability. TGE on mycorrhiza establishment and plant performance were evaluated in their clonal and sexual offspring, which experienced the parental or all non‐parental environments. Consistently in both generations, mycorrhiza improved plant growth at low P availability, but had no or even negative effect at high P availability, concomitantly with decreased root colonization by the arbuscular mycorrhizal (AM) fungus. TGE due to mycorrhiza was generally stronger in sexually derived offspring, both on mycorrhiza formation and plant growth. In sexual offspring, parental mycorrhizal status was adaptive if the offspring's mycorrhizal status was of disadvantage: for mycorrhizal offspring growing in high P availability and for non‐mycorrhizal offspring at low P availability. Synthesis : Our results suggest that clonal and sexual reproduction are under different evolutionary pressures, leading to the development of stronger TGE mechanisms in response to mycorrhizal symbiosis in the latter. The complexity of the observed effects highlights the need for disentangling the mechanisms contributing to the TGE in clonal and sexual reproduction. Our study underlines the importance of considering reproductive strategies and the interplay between environmental factors and TGE in understanding the ecological and evolutionary dynamics of plant–symbiotic interactions.