A population genetics approach to evaluating weed movement and the role for area wide weed management

This study used a population genetics approach to assess weed movement within and across each of three regions in Australia – the Darling Downs, the Riverina, and Sunraysia. Populations of three weed species; fleabane (Conyza bonariensis); feathertop Rhodes grass (Chloris virgata); and annual ryegrass (Lolium rigidum) were collected across varying land uses and gene flow was investigated using a genotyping by sequencing approach.

Annual ryegrass populations were very similar, with very little genetic differentiation across sites sampled in the Riverina region. This suggests high levels of mixing within the region. Feathertop Rhodes grass populations sampled across the Darling Downs were also genetically similar, indicating high levels of gene flow and movement in this weed species. While some evidence of long-distance dispersal between regions was found, fleabane populations revealed surprising evidence of genetic differences within the Riverina region, and between the Sunraysia and Riverina regions. The research suggests that herbicide resistance in annual ryegrass and feathertop Rhodes grass is moving widely across the regional landscape.

Hereward, J., Malone, J., Ratcliff, C., Quarisa, I., Kirby, R., Morgan, T., & Preston, C. (2022). A population genetics approach to evaluating weed movement and the role for area wide weed management. Proceedings of the 22nd Australasian Weeds Conference Adelaide September 2022. ISBN:, 190–193. https://caws.org.nz/wp-content/uploads/2024/08/22AWC_Proceedings_Rev_B_SEC_IDX-1-Edited-by-Melland-et-al-2022-1.pdf#0242-page1