The geografical origin of the Pinus sylvestris seed influence community and co-occurrence of the fungal and bacterial endophytes in common garden experiment
Below-ground microbial communities, particularly endophytic communities, play an important role in the establishment and maintenance of plant by nutrient acquisition and helping plants to withstand harmful abiotic and biotic stress. While plant phylogeny or taxonomic distance among plant hosts is recognized to be associated with variation in the root fungal and bacterial communities, the impact of host plant origin within a specific plant species on the root endophytic community has received less attention. Scots pine (Pinus sylvestris L.) is characterized by a very wide distribution in Europe and Asia. In Poland, it is one of the most important forest trees growing in different environmental conditions, which influence the variability of physiological and morphological characteristics. To determine the effect of plant origin in different growing seasons, we harvested the roots of 60 individual trees of P. sylvestris representing six different geographical origins in two   seasons that were grown in a common garden site. Totally, 936 operational taxonomic units (OTUs) of endophytic fungi and 2 145 OTUs of endophytic bacteria have been identified at a 97% sequence similarity level using Illumina MiSeq sequencing of the ITS and 16S regions of fungi and bacteria, respectively, from the roots of P. sylvestris trees representing six different geographical origins. OTUs richness of endophytic fungi and bacteria was not influenced by tree origin or season. However, the Shannon diversity index of endophytic fungi was influenced by the season. The community composition of endophytic fungi and bacteria was influenced by tree origin and season and was correlated with host root biochemical parameters  . Furthermore, the occurrence and abundance of some endophytic fungi and bacteria were biased among different origins of P. sylvestris and depended on the growing season.  This finding enhances our understanding of the relationship between host plant origin and root endophytic community assembly, which has particular implications for tree yield and restoration success.