O. Oueslati* and M. Ben-Hammouda
Laboratory of Crop/Cereal Physiology, Ecole Supérieure d’Agriculture du Kef/Boulifa. 7119 Le Kef/ Tunisia.
* Corresponding author: Phone number: 0021678238038; E-mail:
Monoculture of barley, where direct drilling is applied as mean of conservation agriculture, may encounter allelopathic risk. Both tissue leachates and root exudates of a crop could persist in the soil with a high depressive potential for the subsequent one. Most studies on barley allelopathy were on above-ground residues and little is known about the allelochemicals released in to the soil by living residues. Auto-toxicity of extracts from soils cultivated with 4 barley varieties (‘Manel’, ‘Martin’, ‘Esperance’, ‘Rihane’) was studied using seedling growth bioassays, with ‘Manel’ as the test-variety. To investigate the role of phenolics in barley auto-toxicity, inhibition of radicle growth by soil extracts was regressed on total-phenolics and 5 phenolic acids (p-hydroxybenzoic, ferulic, vanillic, syringic, p-coumaric) contents of all soil extracts. Only radicle growth bioassays permitted the detection of barley auto-toxicity expressed by soil extracts. Radicle growth inhibition by soil extracts from a non-cultivated soil (soil-Control) was not significant, which was not the case for extracts of cultivated ones. Such result suggests that, allelochemicals were essentially released by plant tissues (leachates) and root exudates into the rhizosphere. No significant correlation was found between radicle growth inhibition by soil extracts and total-phenolic contents, though this content varied considerably among the 4 tested varieties. Three phenolic acids (vanillic, syringic, p-coumaric) were identified in soil extracts. As for total-phenolic, no significant correlation was found between radicle growth inhibition by soil extracts and phenolic acids contents. This is an indication that other allelochemicals highly determine barley auto-toxicity.
Keywords: barley varieties, soil extracts, bioassays, phenolic acids, total-phenolics.
RECEIVED: Month Day, 2016
ACCEPTED: Month Day, 2016