Temporal shifts in endophyte bacterial community composition of sessile oak (Quercus petraea) are linked to foliar nitrogen, stomatal length, and herbivory

Luigimaria Borruso; Camilla Wellstein; Alessia Bani; Sara Casagrande Bacchiocchi; Ania Margoni; Rita Tonin; Stefan Zerbe; Lorenzo Brusetti

doi:10.7717/peerj.5769

Temporal shifts in endophyte bacterial community composition of sessile oak (Quercus petraea) are linked to foliar nitrogen, stomatal length, and herbivory

PeerJ. 2018 Oct 12:6:e5769. doi: 10.7717/peerj.5769. eCollection 2018.

Authors

Luigimaria Borruso^#¹, Camilla Wellstein^#¹, Alessia Bani¹, Sara Casagrande Bacchiocchi¹, Ania Margoni¹, Rita Tonin¹, Stefan Zerbe¹, Lorenzo Brusetti¹

Affiliation

¹ Faculty of Science and Technology, Free University of Bozen/Bolzano, Bolzano, Italy.

^# Contributed equally.

Abstract

We studied the relationship between plant functional foliar traits and the endophytic bacterial communities associated in trees, taking the example of sessile oak (Quercus petraea (Matt.) Liebl). Forty-five samples with replicates of eight leaves per sample were collected in spring, summer and autumn. Bacterial community diversity was analyzed via Automated Ribosomal Intergenic Spacer Analysis (ARISA). The leaf traits specific leaf area, level of herbivory, stomatal number, stomatal length, carbon and nitrogen concentration were measured for the leaves of each sample. For statistical analysis, linear mixed effect models, the Canonical Correlation Analysis (CCA) and Non-Parametric Multivariate Analysis of Variance (NPMANOVA) were applied. Herbivory, nitrogen and carbon concentration were significantly different in autumn compared to spring and summer (p value < 0.05), while stomatal length was differentiated between spring and the other two seasons (p value < 0.01). The seasonal differentiation of the bacterial community structure was explained by the first and second axes (29.7% and 25.3%, respectively) in the CCA. The bacterial community structure significantly correlated with herbivory, nitrogen concentration and stomatal length. We conclude that herbivory, nitrogen content, and size of stomatal aperture at the leaf level are important for endophyte colonization in oaks growth in alpine forest environments.

Keywords: Bacteria; Biological interaction; Forest; Leaf traits; Phyllosphere; Seasonality.

Grants and funding

This work was supported by the project “Effects of forest aerial fertilization on the microbial communities of coniferous tree phyllosphere, residuosphere and rhizosphere –MICRONITRAIR” (CUP: I52I13000180005). Partial contributions came from the project entitled “Multidisciplinary characterization of a forest-ecosystem supersite –MULTFOR” (CUP: I52I13000260005). Both projects were granted by the Free University of Bozen-Bolzano. Finally, Luigimaria Borruso received a grant from the “Transdisciplinary Environment and Health Research Network South Tyrol” (TER). There was no additional external funding received for this study. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.