BackgroundSome tree species can become hundreds and even thousands years old. However, other species only grow for a few decades. This lifespan is genome dependent and longevity of trees appears positively correlated with increased numbers of defence related genes and negative plant soil feedback causes a short life span. In addition to defence related genes, microbiomes of the plant are important for its growth and health. However, the role of microbiomes in tree longevity has never been studied. To test whether the microbiomes of centuries-old trees reflect absence of such negative plant soil feedback and whether they harbour microbes with antagonistic activities against their major pathogens, we used a chrono-series of Chinese chestnut (Castanea mollissima) from a Ming orchard at the Great Wall. It has trees of various ages ranging from centuries to tens of years and the oldest tree in this orchard is more than 800 years old. This orchard provides unique opportunities to test the hypothesis that the root microbiome composition of trees with the potential to become old, does not depend on the age of the tree and is not affected by negative plant soil feedback.ResultsMicrobiomes of soil, rhizosphere and endophytic compartment from young (~10 years) and old trees (up to ~800 years) were analysed by meta-amplicon sequencing, Mantel test and linear regression analysis. Using the Bray-Curtis dissimilarity measure on rarefied OTUs, PCoA plots showed that in each compartment, microbiomes of the young tree clustered well with that of the old trees. Mantel test and linear regression analyses of the relation between Bray-Curtis dissimilarity values and age difference, showed that these values remain rather similar with increasing age difference. Moreover, bioactivity tests showed that the most abundant OTU has strong antagonistic activities against 2 major pathogens of chestnut.ConclusionsWe showed that the root and soil microbiomes of a chrono-series of chestnut trees, ranging from 8 to about 800 years are similar. This strongly indicates that Chinese chestnut is able to avoid a negative feedback with its soil, establish root microbiomes that are age independent and this can contribute to its longevity.