The plant leaf hosts a diverse microbial community that influences stress tolerance, herbivore and pathogen resistance, and decomposition. However, the factors that determine the makeup of and changes to this community remain largely unknown. We hoped to investigate the extent to which host genetic control and priority effects contribute to diversity and community structure in leaf fungal communities. We sampled the fungal microbial community in and on switchgrass (Panicum virgatum) leaves over the course of a growing season for one hundred fully sequenced host genotypes in a common garden in Michigan, as well as for ten genotypes in Texas, Missouri, and South Dakota. We sequenced the ITS region of the fungal genomes to determine species composition. We measured phenological, morphological, and disease response traits in the hosts throughout the season to assess the degree to which host phenotypes covary with microbial diversity.
Results/Conclusions
Our results suggest that the host genotype exerts an unexpectedly high control on the leaf fungal community, as genetic distance between host plants was clearly correlated with community differences, particularly in post-flowering plants (Mantel test; n=44, r = 0.3767, p < 0.001). Changes between early- and late season leaves showed an overall increase in taxon diversity, but less differentiation between communities on individual host plants, presumably as successful fungal symbionts become established in host leaves. There was comparatively little influence on the community of an exogenous pathogenic fungus, switchgrass rust (Puccinia novopanici). These promising results will be soon followed by more sites and time points as sequencing is completed. We hope that further data will corroborate our results and show that the leaf fungal community is strongly structured by host genetic makeup, and exhibits classical succession dynamics over the course of the growing season.