Allelopathic Effect of Barley (Hordeum vulgare) and Rapeseed (Brassica napus) Crops on Early Growth of Acetolactate Synthase (ALS)-Resistant Glebionis Coronaria

Glebionis coronaria is a serious threat to cereal production in Northern Tunisia. Previous results showed that G. coronaria has developed resistance to acetolactate synthase (ALS)-inhibiting herbicides which limits their use in cereal cropping systems. The use of allelopathic crops has been reported as a potential alternative to herbicides to control resistant weed populations. The aim of this study is to evaluate the effect of five allelopathic crops on the early growth of G. coronaria. In vitro experiments using aqueous extracts of different crops and in pots experiments with increasing rates of barley (Hordeum vulgare) and rapeseed (Brassica napus) residues were performed for this purpose. All tested crops showed allelopathic effects on G. coronaria and were able to reduce its root length at the concentration of 50 g/L. Barley and rapeseed were the most effective crops, with 70% and 60% of root length reduction, respectively. An aqueous extract concentration study with five increasing concentrations of 12.5, 25, 50, 75, and 100 % was performed with these two crops, and root length was significantly reduced with increasing concentration, being up to 80% with the highest aqueous extract concentration of barley. The in vitro results were supported by the in pots experiment: Shortest roots length and highest dry mass reduction were obtained by the highest barley (0.64 g/kg) and rapeseed (8 g/kg) residue concentrations. This study confirmed the allelopathic potential of both barley and rapeseed in reducing the early growth of ALSresistant G. coronaria, suggesting the effectiveness of these crops if integrated with other control measures for the management of resistant population of G. coronaria in cereal fields.