Evaluation of different methods for breaking cypsela dormancy in two local populations of Scotch thistle (Onopordum acanthium L.) collected from the west and northwest of Iran

Abstract

Scotch thistle ( Onopordum acanthium L.) is a weed species on farmlands and pastures in parts of the west and northwest of Iran. Cypselas can remain in the soil seedbank over a prolonged period due to varying degrees of dormancy. This study examined different methods for breaking cypsela dormancy in two local populations of Scotch thistle at the research laboratory of the Faculty of Agriculture of Azarbaijan Shahid Madani University in 2020. In these experiments, the effects of sulfuric acid, wet and dry prechilling, potassium nitrate, and gibberellic acid were evaluated on the breaking of dormancy. All the experiments were conducted as a completely randomized design with four replications and two runs. The response of two local populations of Scotch thistle were similar, and no significant difference was observed. The experiment treatments significantly increased cypsela germination compared with the control. The maximum germination percentages were observed in cypselas soaked in 98% sulfuric acid for 10 min (60.60%), KNO3 for 96 h (69.36%), GA3 for 48 h (88.43%), and wet prechilling for 72 h (34.61%). Although prechilling increased germination, it was suggested that germination could be more than the recorded values if the duration of wet prechilling was increased. The best cypsela germination rate, mean germination time, T50, and radicle and plumule length were observed after soaking in GA3 for 48 h and KNO3 for 96 h. It seems that water-soluble inhibitors in the embryo and probably the cypsela coat cause seed dormancy in this weed species. These findings could help develop effective management strategies associated with the dormancy of cypselas for this species.