Farming and climate legacies shape the seed microbiota and offspring drought responses in wheat

Seeds link parental environments to offspring establishment, but whether seed-associated bacteria retain signatures of farming and climate legacies across plant generations remains unclear. Here, we characterized epiphytic and endophytic bacterial communities of winter wheat seeds collected from the Global Change Experimental Facility (GCEF) in Germany across three harvest years representing contrasting climates. We then tested how farming (organic versus conventional) and climate (ambient versus future) legacies experienced by maternal plants were associated with offspring rhizosphere bacterial communities and plant performance under drought in the greenhouse. Harvest year was the dominant driver of grain dry weight and seed-associated bacterial communities. Climate legacy additionally affected seed epiphytic communities, whereas farming legacy was expressed in the endophytic diversity. Germination was higher overall for seeds from the conventional than the organic farming legacy and from the ambient than the future climate legacy. A small subset of unique seed-associated ASVs was detected in offspring rhizospheres. Although these ASVs occurred at low relative abundance in seeds (<1%), they accounted for up to approximately 40% of rhizosphere relative abundance under drought. Together, these findings show that seeds retain bacterial signatures of parental farming and climate legacies and that a subset of seed-associated ASVs remains detectable and can become abundant in offspring rhizospheres under drought.