Soil microbial community responses to the fungal endophyte Neotyphodium in Italian ryegrass
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Cool-season grasses commonly harbor fungal endophytes in their aerial tissues. However the effects of these symbionts on soil microbial communities have rarely been investigated. Our objective was to explore microbial community responses in soils conditioned by plants of the annual grass Lolium multiflorum with contrasting levels of infection with the endophyte Neotyphodium occultans. At the end of the host growing season, we estimated the functional capacity of soil microbial communities (via catabolic response profiles), the contribution of fungi and bacteria to soil activity (via selective inhibition with antibiotics), and the structure of both microbial communities by molecular analyses. Soil conditioning by highly infected plants affected soil catabolic profiles and tended to increase soil fungal activity. We detected a shift in bacterial community structure while no changes were observed for fungi. Soil responses became evident even without changes in host plant biomass or soil organic carbon or total nitrogen content, suggesting that the endophyte modified host rhizodepositions during the conditioning phase. Our results have implications for the understanding of the reciprocal interactions between above and belowground communities, suggesting that plant-soil feedbacks can be mediated by this symbiosis.
KeywordsAbove and below ground interactions Aerial symbiosis Neotyphodium endophytes Lolium multiflorum Soil fungi and bacteria
Lolium multiflorum population highly infected with the endophyte Neotyphodium occultans
Lolium multiflorum population lowly infected with the endophyte Neotyphodium occultans
catabolic response profile
denaturing gradient gel electrophoresis
restriction fragment length polymorphism
We thank the owners of “Las Chilcas” farm, who kindly allowed us to take the soil used in the experiment and Marcos Texeira by helping us with statistical bootstrap. We are also grateful to Maria Semmartin and the anonymous reviewers who provided very valuable comments on the manuscript. This work was supported by grants from CONICET-ANPCyT (PICT 1728) and the Microbiology Department of Faculty of Agronomy, University of Buenos Aires.
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