Inheritable Epigenetic Memory Induced by Parental Salt Stress Influences Transgenerational Plasticity of <i>Phragmites australis</i>

ABSTRACT Phenotypes of estuarine plants are influenced by salt stress experienced in both the current generation and by their parents, a phenomenon potentially regulated by DNA methylation. In clonal plants, DNA methylation information is effectively transmitted across generations, further influencing offspring phenotypes. However, the role of DNA methylation in clonal transgenerational plasticity and its heritable stability remains poorly understood across various genotypes of wild plants. To this end, we employed controlled genotype × environment interaction experiments to investigate phenotypic responses and DNA methylation in parental and offspring generations of Phragmites australis under salt stress conditions. Furthermore, we investigated the stability of DNA methylation inheritance across three generations exposed to continuous salt stress. Our results demonstrated that parental salt stress significantly increased plant height, maximum leaf area, and rhizome nodes of P. australis offspring from certain genotypes subjected to salt stress similar to their parents, compared to offspring of unstressed parents. Parental salt stress induced an increase in CHG hemi‐methylation and a decrease in CG methylation, potentially modulating changes in offspring plant height, maximum leaf area, and rhizome nodes. Moreover, multigenerational salt stress resulted in a persistent reduction in CG methylation and a cumulative elevation of CHG hemi‐methylation in specific genotypes. These findings reveal that offspring phenotypes in P. australis are jointly determined by genetic background and both parental and offspring environments, mediated through epigenetic modifications, which further advances our understanding of evolutionary adaptation strategies in clonal plants.