REGULAR ARTICLE Metabolomic approaches for the identification of flavonoids associated with weed suppression in selected Hardseeded annual pasture legumes Sajid Latif & Saliya Gurusinghe & Paul A. Weston & Jane C. Quinn & John W Piltz & Leslie A Weston Received: 19 February 2019 /Accepted: 16 July 2019 # Springer Nature Switzerland AG 2019 Abstract Background and aims Weed suppressive potential of annual pasture legumes has been previously described, the mechanism of interference with weeds has not been clearly elucidated. We, therefore, aimed to delineate the role of secondary metabolites synthesized and released by pasture legumes through a series of studies to: 1) characterize key metabolites present in plant tissues, residue and the rhizosphere and 2) correlate their pres- ence with weed suppressive properties. Methods Field and in vitro experimentations coupled with targeted and non-targeted metabolic profiling was performed to evaluate the abundance of key phytotoxic metabolites using UHPLC QTOF-MS. Further, those metabolites strongly correlated with weed suppression and phytotoxicity were predicted by chemometric anal- yses and their concentration evaluated in field soils collected from the same legume site. Results Field experimentation, methanolic extracts and dried residues of Biserrula pelecinus L. and Ornithopus compressus L. exhibited marked phytotoxicity in a se- ries of laboratory experiments. Metabolic profiling re- vealed that both foliar tissues and rhizosphere soils of pasture legumes possessed a high abundance of flavo- noids and their precursors. Chemometric analyses sug- gested the strong association of quercetin, isoquercetin, kaempferol, and kaempferol-7-O-glucoside with weed suppression under field conditions. Specifically, the abundance of quercetin and kaempferol was significant- ly higher in soils collected from established stands of biserrula and yellow serradella in contrast to arrowleaf, gland and subterranean clover. Conclusion Current study provided an evidence for the role of certain annual legume-produced flavonoids in weed suppression in southern Australia and further in- sight into their localization and release in the soil rhizosphere. Keywords Annual hard-seeded pasture legumes . Phytotoxicity . Root exudation . Weed suppression . Chemometric analysis . Metabolic profiling . Flavonoids Plant Soil https://doi.org/10.1007/s11104-019-04225-4 Responsible Editor: Eric Paterson. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11104-019-04225-4) contains supplementary material, which is available to authorized users. S. Latif (*) : S. Gurusinghe : P. A. Weston : J. C. Quinn : J. W. Piltz : L. A. Weston Graham Centre for Agricultural Innovation (NSW Department of Primary Industries), Locked Bag 588, Wagga Wagga, NSW 2678, Australia e-mail: slatif@csu.edu.au S. Latif : J. C. Quinn School of Animal and Veterinary Sciences, Charles Sturt University, Wagga Wagga, NSW 2678, Australia P. A. Weston : L. A. Weston School of Agriculture and Wine Sciences, Charles Sturt University, Wagga Wagga, NSW 2678, Australia J. W. Piltz NSW Department of Primary Industries, Agricultural Institute, Wagga Wagga, NSW 2650, Australia