BTE endophytes. Interaction between growth environment and host progeny shape fungal endophytic assemblages in transplanted Fagus sylvatica

Fungal endophytes are an integral part of the leaf microbiome of forest trees. Most of these endophytes are horizontally transmitted, however little is known about their assembly drivers. Endophytic assemblages differ in composition according to geography and host individuals. In addition, climate and genetic diversity are also reported to lead to host plant adaptation. To determine the impact of the host progeny and respective adaptation to environmental conditions on endophytic assemblages, we designed a transplantation experiment in beech trees (Fagus sylvatica). Beech nuts were collected from distant geographical regions and germinated in a common greenhouse. One-year-old beech seedlings were transplanted to the different locations and the leaf-endophytic assemblages were characterized in the second growth season after planting by cultivation-independent metabarcoding. The chlorophyll and flavonoid content of the respective leaves were also measured. The results revealed host progeny effects in shaping leaf-endophytic fungal assemblages, that might be concealed by major geographical effects. We hypothesise and discuss possible interactions of different assembly drivers.