Common garden experiments suggest terpene-mediated associations between phyllosphere microbes and Japanese cedar

Plant-microbe interactions in the phyllosphere provide invaluable information on plant ecology, with implications for ecosystem functioning and plant-atmosphere feedbacks. The composition of phyllosphere microbes varies significantly depending on host lineages, geographic regions, and climatic conditions. However, the factors driving these variations in interactions with plants remain poorly understood. Biogenic volatile organic compounds (BVOCs) emitted by plants may be important in these interactions. Here, we quantified the composition of phyllosphere microbial communities and terpene emissions from leaves of Japanese cedar (Cryptomeria japonica) trees grown in two common gardens from cuttings collected from natural populations across Japan. Amplicon sequencing revealed that microbial communities differed significantly between gardens and among host populations. Analysis of BVOC profiles showed that the camphene and total terpene emission rates were associated with bacterial composition, whereas that of ent-kaurene was marginally linked to fungal composition. The relative abundances of certain fungal genera that include the species reported to cause disease in Japanese cedar, the emission rates of most monoterpenes and a sesquiterpene β-farnesene were correlated with the climatic conditions at the origin sites of the cedar trees. These findings highlight the intricate relationships between phyllosphere microbes and terpene emission from host trees and suggest the role of climatic factors in shaping these associations.