The Palmer Amaranth Project

Investigation of the recent agricultural invasion of Palmer amaranth

The most agriculturally problematic species in the weedy plant genus Amaranthus is A. palmeri (Palmer amaranth), which has rapidly evolved herbicide resistance: populations of the species are now insensitive to herbicides that target six different biological pathways. Agricultural research has focused on understanding the genetic mutations underlying the resistance mechanisms in Palmer amaranth. However, there has been no genetic investigation of the species’ remarkable range expansion out of the desert Southwest and aggressive invasion into agricultural fields in the eastern U.S. and Central California, and no development of a population genetic framework for the invasion that could relate neutral genetic variation (reflecting demographic changes) to agriculturally-adaptive genetic variation, such as herbicide resistance.

With funding from CSUPERB, we are currently collecting seed and leaf samples from populations of Palmer amaranth across its native range in the southwestern U.S. In collaboration with Dr. Chance Riggins at the University of lllinois, genotyping-by-sequencing analysis will be performed for these populations. Subsequent bioinformatics analysis will allow calculation of genetic diversity and structure metrics for Palmer amaranth across its native range. This study will provide sample collection and preliminary data for a broader collaborative project (with the Riggins lab and Dr. Anil Shrestha at CSU, Fresno) focused on exploring the evolution of agricultural invasiveness and herbicide resistance evolution in the species as a whole, with the applied goal of developing data-driven management strategies designed to curb resistance evolution and spread.