Seed Potato Bacteria Transfer Across Generations Within the Tuber Flesh

Potato crops are susceptible to pathogens and environmental extremes. Microbiomes support plant health and stress tolerance, and microbes can transfer across generations in vegetatively propagated potatoes. However, the extent and functional relevance of this transfer are poorly understood. This study investigated bacterial transfer across three tuber generations, from seed to granddaughter in two potato cultivars, Nadine and Royal Blue. Bacterial communities in the peel and flesh compartments were sequenced. The granddaughter generation was cultivated in two separate fields to determine the consistency of vertical transfer, and the tare soil bacterial community was a proxy for environmental acquisition. The overall community composition was influenced by generation, compartment, cultivar and field. Horizontal acquisition significantly increased across generations and was the primary source, accounting for more than 98% of the granddaughter tuber bacteria. Peel had a significantly higher number of horizontally acquired ASVs than flesh. Only a small set of seed tuber bacteria ASVs were vertically transferred to the granddaughter tubers. The overall vertical transfer probability was 1.8% across compartments, cultivars, and fields, and it was higher in flesh than in peel. Cultivar-specific probabilities were 1.8% for Nadine and 1.5% for Royal Blue. Field variance was minimal, indicating consistent vertical transfer regardless of where the tubers were grown. Taxa with stable vertical transfer included Streptomycetaceae, Xanthobacteraceae, Devosiaceae, Sphingomonadaceae, and Micrococcaceae. Vertically transferred ASVs were predicted to have functions associated with core metabolic and stress response pathways. This study confirmed consistent vertical transfer of bacteria across potato tuber generations, mainly in the flesh.