A bioassay to evaluate plant responses to the allelopathic potential of rhizosphere soil of wild oat (Avena fatua L.)

This study investigates the growth responses of durum wheat (Triticum durum Desf.) seedlings to the allelopathic potential of rhizosphere soil of wild oat (Avena fatua L.) using a new laboratory bioassay. The method consists of the evaluation of 15-day-old wheat seedlings grown in the rhizosphere soil from wild oat. The experiments were performed in a growth chamber, using seven durum wheat varieties ('Chiara', 'Creso', 'Dario', 'Daunia', 'Mediterraneo', 'Meridiano', 'Vesuvio') that were grown in control (non-rhizosphere) soil and rhizosphere soil of wild oat at three seed densities (1,3 and 5 seeds/dish). The inhibition of seedling growth was greater for the leaves than for the root tissue, and the degree of inhibition was cultivar-dependent. HPLC analysis indicated the presence of three potential allelochemicals in the rhizosphere soil of the wild oat: p-coumaric acid, syringaldehyde and vanillin. These preliminary results show the phytotoxic nature of the rhizosphere soil of wild oat and indicate the potential involvement of organic molecules in this growth inhibition of durum wheat.