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This paper describes the range in coumarin concentrations at 90% flowering stage in 149 accessions belonging to 15 Melilotus species grown in a genetic resources field characterisation experiment in Adelaide, South Australia, and determines coumarin concentrations in Melilotus species grown at two contrasting field sites in South Australia (Kybybolite and Keith). In the genetic resources characterisation experiment, the mean coumarin content ranged from 0.06 to 0.753% of dry matter. M. segetalis, M. dentatus, M. sulcatus, M. siculus and M. infestus recorded low (0.06 to 0.113%) coumarin levels while moderate levels (0.332-0.753%) were registered in the other species. The coumarin levels at Kybybolite and Keith sites ranged from 0.095 to 0.943% amongst M. indicus accessions compared to M. siculus (0.007-0.100%) and M. sulcatus (0.007-0.810%). No coumarin was detected in a M. segetalis accession at these two sites. Accessions of M. siculus and an accession of M. segetalis (SA 36979) and of M. sulcatus (SA 40019) could be potential candidates as pasture legumes that can combine tolerance of both salinity and waterlogging, and acceptably low concentrations of coumarin. [ABSTRACT FROM AUTHOR]