Abstract
Fungal root endophytes are plant associates that colonize root tissue internally without causing any obvious harm to their host. Although ubiquitous, this relationship is not well understood. Our objectives were to determine the effects of fungal root endophyte inoculation on plant biomass and nitrogen concentration by conducting an extensive meta-analysis. We also explored the effects of experimental conditions on the host–endophyte relationship. We performed analyses weighted with non-parametric variance on plant response to root endophytes from the Ascomycetes (excluding the Clavacipitaceae), including categorical analyses of 21 experimental factors, ranging from the identity of the host and the endophyte, to the composition of the growing medium. The response of total biomass to endophyte inoculation was 18 % lower than non-inoculated controls, while individually, root biomass, shoot biomass, and nitrogen concentration responses to endophyte inoculation were neutral. The identities of both the host and the endophyte had an influence, as did the original source of the endophyte (whether or not the isolate used originated from the same host species). Experimental conditions also influenced the plant–endophyte relationship, with the most important being the availability and sources of carbon and organic nitrogen, particularly peat moss. Although our analysis demonstrates that overall plant biomass and nitrogen concentration responses to ascomycetous root endophyte inoculation is neutral to negative, these results are somewhat confounded by among-study differences in experimental conditions, which undoubtedly contribute to the high levels of variability in plant response seen in the literature.
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Acknowledgments
We thank the National Sciences and Engineering Research Council of Canada and Saint Mary’s University, Halifax, NS, who provided financial support for this project. We also appreciate helpful comments from anonymous reviewers.
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List of factors and categories used for the categorical analyses (PDF 18 kb)
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Detailed list of data collected for all the studies used to conduct the meta-analysis, including publication from which the studies were extracted, values for the 21 factors used in the analyses as well as values for sample sizes and response ratios (XLSX 87 kb)
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Mayerhofer, M.S., Kernaghan, G. & Harper, K.A. The effects of fungal root endophytes on plant growth: a meta-analysis. Mycorrhiza 23, 119–128 (2013). https://doi.org/10.1007/s00572-012-0456-9
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DOI: https://doi.org/10.1007/s00572-012-0456-9