Using population genetics to understand weed movement in the context of area wide management

Herbicide resistance is a growing threat to agricultural production with increasing numbers of weed species becoming resistant to key herbicides. Following the evolution of herbicide resistance in a weed species it then spreads across a region by the movement of pollen and seeds. Weed mobility is therefore a key factor in the spread of herbicide resistance and highly mobile weeds can rapidly become shared problems.

This study used a population genetics approach to assess weed movement within and across each of three regions: the Darling Downs in Queensland, the Murrumbidgee Irrigation Area in NSW, and the Sunraysia region in Victoria. Weed species were selected based on high potential mobility and the concerns of growers in these regions. In 2020, fleabane (Conyza bonariensis) was collected in the Riverina and Sunraysia, annual ryegrass (Lolium rigidum) collected in the Riverina, and feathertop Rhodes grass (Chloris virgata) collected in the Darling Downs.

Population genetics analyses were conducted using a genotyping by sequencing approach, genetic differentiation was low between ryegrass populations and also feathertop Rhodes, indicating high levels of geneflow. Fleabane, however, had higher genetic differentiation within a region and similar patterns of genetic structure across the two seasons.

By sampling the same populations across two seasons we were able to use parentage analysis to identify the movement of weed individuals at a regional scale.

Hereward, J., Preston, C., Graham, S., Ratcliff, C., & Llewellyn, R. (2024). Using population genetics to understand weed movement in the context of area wide management. Proceedings of the 23rd Australasian Weeds Conference Brisbane August 2024. ISBN: 978-0-646-70156-1, 86. https://acrobat.adobe.com/id/urn:aaid:sc:AP:24e14be0-0ebf-450d-8433-5b3c7fd07a45?viewer%21megaVerb=group-discover