A modified bioassay for the evaluation of the allelopathic potential of barley (Hordeum vulgare L. subsp. vulgare) and great brome (Bromus diandrus Roth.)

Description of the subject. The present study focused on the description of the allelopathic interactions between wild and crop species that may occur in a given ecosystem. Objectives. The evaluation of the allo- and autoinhibition activity of root exudates of barley ( Hordeum vulgare L. subsp. vulgare ) and great brome ( Bromus diandrus Roth.) seedlings by water-soluble allelochemicals. Method. The allelopathic activities of five Tunisian barley genotypes (modern varieties and landraces), one Saudi Arabian barley landrace and great brome were assessed using a modified laboratory bioassay – named, ‘seedling-after-seedling agar method’ Results. Barley or great brome reduced to a greater extent the root growth as compared to the shoot growth of receiver species. The response of the root system architecture of the great brome towards barley root exudates was studied in detail. All the measured root traits were highly sensitive to the toxic effect of barley. In our conditions, the allelopathic activity of barley root exudates had no apparent relationship with the size of the root and a prominent action of genetic determinants in the allelopathic potential between genotypes is proposed. The alloinhibitory activity of barley or great brome root exudates was dependent on the receiver species but always higher than the autoinhibition potential. The autoinhibition in barley proved to depend on whether the genotypes used as donor and receiver are identical or different, suggesting a specific interaction of allelochemicals with the receiver plant. These molecules seem to be the main actors in the allelopathic barley potential in the view that variations in the external pH have no evident relevance in the inhibition process. Conclusions. Barley and great brome exude molecules in their surrounding that affect the growth of receiver plants suggesting that these compounds might contribute to the plant community dynamics.