Publications

Lolium rigidum (annual or rigid ryegrass) is a widespread annual weed in cropping systems of southern Australia. Seeds exhibit dormancy at dispersal and require a period of dry after-ripening to release dormancy, before germination and emergence can occur.

This study investigated a possible link between seed dormancy and herbicide resistance status of Lolium rigidum (annual or rigid ryegrass). Mature seeds were collected from 406 populations across the 14-million hectare grain belt of southern Western Australia.

Herbicide rate cutting is an example of poor use of agrochemicals that can have potential adverse implications due to rapid herbicide resistance evolution. Recent laboratory-level studies have revealed that herbicides at lower-than-recommended rates can result in rapid herbicide resistance evolution in rigid ryegrass populations.

Seeds in the field experience wet-dry cycling that is akin to the well-studied commercial process of seed priming in which seeds are hydrated and then re-dried to standardise their germination characteristics.

In two different locations of the Western Australian “wheatbelt”, Lolium rigidum (rigid ryegrass) seeds were collected from organic fields (no herbicide use) and neighbouring conventional fields (persistent herbicide use), the latter infested with herbicide-resistant plants, to investigate the occurrence of gene flow among field populations as revealed by herbicide resistance gene transfer.

The dynamics of herbicide resistance evolution in plants are influenced by many factors, especially the biochemical and genetic basis of resistance. Herbicide resistance can be endowed by enhanced rates of herbicide metabolism because of the activity of cytochrome P450 enzymes, although in weedy plants the genetic control of cytochrome P450-endowed herbicide resistance is poorly understood.