Host genotype and aerial spore communities influence the needle mycobiome of Norway spruce

Background/Question/Methods

: Plant associated microbes are of a major importance for plant fitness. Among the organisms living inside of plants, leaf-inhabiting fungi can provide the host with stress tolerance or pathogen protection. Currently, the factors shaping the composition of the leaf mycobiome are still under investigation. In this study, we aimed to understand the main drivers of the assembly of the fungal communities living inside of the needles of Norway spruce (Picea abies (L) Karst.). To achieve this goal, we used a unique set of sites containing clonal replicates of genotyped Norway spruce and a spore trapping strategy, and we characterized the needle and air mycobiome by high-throughput sequencing of the fungal ITS2 region. Since the same genotypes of Norway spruce were replicated across sites in which we characterized the air mycobiome, we could disentangle the relative effect of host genotype, site, host phenotypic traits, and composition of the aerial spore communities on the assembly of the needle mycobiome of Norway spruce trees.

Results/Conclusions

: We found that the composition of the needle mycobiome was mainly influenced by the tree genotype, and genotypes with high genetic similarity had a more similar mycobiome. Besides the effect of the host genotype, the needle mycobiome was associated with the composition of the air mycobiome available at the site. Needle and air mycobiome shared 80% of the members of the communities. Moreover, changes in relative abundance of taxa in the needle mycobiome across sites were associated with changes in the relative abundance of those taxa in the air mycobiome. Our work highlights the role of host intraspecific variation and horizontal transmission of leaf-inhabiting fungi in shaping the mycobiome of trees. These findings add new insights on ecological processes in which plant-microbiome interactions influence plant diversity.