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

Abstract

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. • Most leaf endophytic fungi are acquired from the surrounding environment. • Endophytic assemblages are mainly shaped by climate, followed by the host. • Interactions are often concealed by dominant geographical effects. • The host adaptation to the local climate is reflected by the phytochemistry. • Phytochemistry has a weak influence on the associated endophytic assemblages.