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Root exudate fingerprint of Brachiaria humidicola reveals vanillin as a novel and effective nitrification inhibitor

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Title Root exudate fingerprint of Brachiaria humidicola reveals vanillin as a novel and effective nitrification inhibitor
 
Creator Egenolf, Konrad
Schöne, Jochen
Conrad, Jürgen
Braunberger, Christina
Beifuß, Uwe
Arango, Jacobo
Rasche, Frank
 
Subject forage
soil biology
nitrogen fixation
nitrification inhibitors
allelopathy
phenolic compounds
Urochloa
Nitrosomonas
 
Description Introduction: Biological Nitrification Inhibition (BNI) is defined as the plant-mediated control of soil nitrification via the release of nitrification inhibitors. BNI of Brachiaria humidicola (syn. Urochloa humidicola) has been mainly attributed to root-exuded fusicoccane-type diterpenes, e.g., 3-epi-brachialactone. We hypothesized, however, that BNI of B. humidicola is caused by an assemblage of bioactive secondary metabolites.

Methods: B. humidicola root exudates were collected hydroponically, and metabolites were isolated by semi-preparative HPLC. Chemical structures were elucidated by HRMS as well as 1D and 2D NMR spectroscopy. Nitrification inhibiting potential of isolated metabolites was evaluated by a Nitrosomonas europaea based bioassay.

Results and discussion: Besides previously described brachialactone isomers and derivatives, five phenol and cinnamic acid derivatives were identified in the root exudates of B. humidicola: 2-hydroxy-3-(hydroxymethyl)benzaldehyde, vanillin, umbelliferone and both trans- and cis-2,6-dimethoxycinnamic acid. Notably, vanillin revealed a substantially higher nitrification inhibiting activity than 3-epi-brachialactone (ED50 ∼ 12.5 μg·ml−1, ED80 ∼ 20 μg·ml−1), identifying this phenolic aldehyde as novel nitrification inhibitor (NI). Furthermore, vanillin exudation rates were in the same range as 3-epi-brachialactone (1–4 μg·h−1·g−1 root DM), suggesting a substantial contribution to the overall inhibitory activity of B. humidicola root exudates. In relation to the verification of the encountered effects within soils and considering the exclusion of any detrimental impact on the soil microbiome, the biosynthetic pathway of vanillin via the precursor phenylalanine and the intermediates p-coumaric acid/ferulic acid (precursors of further phenolic NI) might constitute a promising BNI breeding target. This applies not only to Brachiaria spp., but also to crops in general, owing to the highly conserved nature of these metabolites.
 
Date 2023-12
2023-12-26T07:54:11Z
2023-12-26T07:54:11Z
 
Type Journal Article
 
Identifier Egenolf, K.; Schöne, J.; Conrad, J.; Braunberger, C.; Beifuß, U.; Arango, J.; Rasche, F. (2023) Root exudate fingerprint of Brachiaria humidicola reveals vanillin as a novel and effective nitrification inhibitor. Frontiers in Molecular Bioscience 10:1192043. ISSN: 2296-889X
2296-889X
https://hdl.handle.net/10568/135917
https://doi.org/10.3389/fmolb.2023.1192043
 
Language en
 
Rights CC-BY-4.0
Open Access
 
Format 1192043
application/pdf
 
Source Frontiers in Molecular Biosciences