Screening for waterlogging tolerance in subterranean clover (Trifolium subterraneum L.)

Subterranean clover (subclover, Trifolium subterraneum L.), is the most widely sown annual pasture legumein southern Australia, but winter waterlogging can cause extensive biomass reductions. Determining anefficient and non-destructive screening method for waterlogging tolerance is crucial for subclover breedingprograms to identify parents and progeny with tolerance. Tolerance to short (21 days) and extended (35days) periods of waterlogging, relative to non-waterlogged conditions, was assessed among nine subclovercultivars across the three subclover subspecies (subterraneum, yanninicum and brachycalycinum) in acontrolled environment glasshouse. Treatments, imposed after 28 days growth, comprised a free-drainingcontrol and waterlogging. A range of measurements was compared with shoot dry weight and shoot relativegrowth rate. Easily-assessed indicators of short-term waterlogging tolerance were less effect on petiolelength, high leaf chlorophyll content and low petiole anthocyanin, while extended waterlogging tolerancewas indicated by lower reduction of leaf size and high stomatal conductance.