Comparative metabolomics reveal the participation of soybean unique rhizosphere metabolites in susceptibility and resistance of host soybean to Phytophthora sojae

AimsPhytophthora root rot (PRR) of soybean is a destructive soil-borne disease caused by Phytophthora sojae (Ps). Isoflavonoids daidzein and genistein in soybean root exudates mediate soybean susceptibility. However, no attention has been paid to the inhibitors in the resistant soybean root exudates. This study aims to identify the metabolites which participate in host susceptibility and resistance in soybean root exudates.MethodsThe metabolomes of rhizosphere soil of a pair soybean near-isogenic lines Williams (rps, susceptible) and Williams 82 (Rps1k, resistant) were analyzed by LC–MS. The effects of rhizosphere soil on Ps were determined. The expression levels of core metabolites synthetase related genes were quantified by qRT-PCR.ResultsClear differences were found in the rhizosphere metabolites between susceptible Williams and resistance Williams 82. Higher accumulations of daidzein and genistein were observed in susceptible Williams. Other abundant flavones and isoflavonoids closely related to daidzein and genistein likely participate in the susceptibility of Williams to Ps. Antibiotics mannan, cis-β-D-glucosyl-2-hydroxycinnamate, vanillic acid and 2-(4-hydroxyphenyl) ethanol are likely related to pre-existing resistance of Williams 82 to Ps. The rhizosphere metabolites altered greatly under Ps inoculation. Weak and strong induced resistance to Ps were observed in Williams and Williams 82. Less flavones and isoflavonoids, and abundant 13-L-hydroperoxylinoleic acid are likely related to the weak induced resistance of Williams to Ps. While 9,10,13-TriHOME, 9,12,13-TriHOME, N2-acetyl-L-ornithine, paromomycin and 2- (4-hydroxyphenyl) ethanol are likely related to the induced resistance of Williams 82 to Ps. Additionally, there were other abundant metabolites in Williams and Williams 82 rhizosphere. Functions of these metabolites in pre-existing and induced resistance to Ps need to be further studied.ConclusionsDifferent core metabolites in the rhizosphere soil participate in the susceptibility and resistance of host soybean to Ps.