Morphological, cytological and ecological discrimination of Bromus rigidus from Bromus diandrus.
Morphological characters of different populations of brome found in the northern wheatbelt of Western Australia pointed to the presence of B. diandrus and another taxon, probably B. rigidus. This was later confirmed by the counts of somatic chromosomes from root meristems of seedlings from different accessions. This is the first report from Western Australia of B. rigidus, a potentially serious weed of crops on the sandplains of the northern wheat-belt. The accessions of B. diandrus exhibited a much faster loss of seed dormancy than B. rigidus. Duration of seed dormancy coupled with rapid germination of non-dormant seeds of B. diandrus is likely to render it both more prone to premature germination following summer rainfall and more susceptible to pre-sowing cultural and herbicide treatments following break of the season. B. rigidus appears to be well adapted to the Mediterranean climate of the northern wheat-belt of Western Australia, and is likely to demonstrate seed carryover from one season to the next.