Allelopathic effects of downy brome extracts on germination and seedling growth in wheat genotypes

Abstract

Phytotoxicity of downy brome (Bromus tectorum) extracts on bread wheat (Triticum aestivum) and durum wheat (Triticum durum) was investigated. Water extracts of downy brome were bioassay on germination and seedling growth of both wheat species to: (i) test the heterotoxicity of downy brome on wheat, (ii) study the dynamics of allelopathic potential over four growth stages and (iii) identify the most allelopathic plant part of downy brome. Whole downy brome plants were extracted at growth stage 4 (stems not developed enough), whilst for the following growth stages roots, stems, and leaves were extracted separately. Seedling growth bioassays demonstrated that the two wheat species responded differently to the allelopathic potential of downy brome with a greater sensitivity shown by the bread wheats. For both wheat species, radicle growth was more depressed than coleoptile growth, though stimulation of seedling growth was observed for durum wheat. The allelopathic potential of downy brome plant parts were not stable over its life cycle for either bread or durum wheat. It appeared that potential increased near physiological maturity. Leaves and roots were the most phytotoxic downy brome plant parts for bread and durum wheats, respectively. Results suggested that the response by durum wheat and bread wheat varied depending on the source of allelochemicals (plant part) and the growth stage of the downy brome plant. Consequently, downy brome should be considered a depressive prior crop for both durum wheat and bread wheat in a field cropping sequence. * Corresponding Author: Farshad Sorkhi Lalelou  farsorkhy@yahoo.com