Contrary to prevailing assumptions, some of the worst weeds in U. S. croplands are not introduced from elsewhere, but are in fact native species. Some of the best known examples of native U. S. weeds are members of the genus Amaranthus, commonly known as pigweeds. In the relatively short span of a few decades, certain species in this genus have become major pests to row crop production systems both within and outside of their native ranges in North America and elsewhere. The ability to thrive in new environments and climatic conditions, cope with ever-changing weed management regimes, and rapidly evolve resistance to new herbicide modes of action are but a few examples of adaptation in amaranth weed species. With the exception of herbicide resistance in some cases, the genetics underlying adaptive evolution in these species remain largely uncharacterized, as is the case for most weeds and invasive plants.Deciphering the sources of variation and mechanisms involved in the adaptive process is often a challenging and long-term endeavor that requires methodologies and collaborations from multiple disciplines, however this proposal seeks to meet this challenge by building upon a strong foundation of previous work and interdisciplinary experience. The current epidemic of herbicide resistance evolution in Amaranthus provides unique opportunities for connecting basic research in evolutionary biology with applied aspects pertaining to agriculture, weed management issues, and food security. Results of this research will contribute to the development of more sustainable weed management strategies (by understanding how weeds adapt to existing strategies), and thereby benefit the weed management community.Since 2009, we have used molecular markers to survey the occurrence and distribution of multiple herbicide resistance in waterhemp (Amaranthus tuberculatus) populations across Illinois and adjacent states. More recently, our survey work was broadened to include monitoring the northern invasion of Palmer amaranth (A. palmeri). Populations of Palmer amaranth are now known to occur sympatrically with waterhemp and other weedy pigweed species in many areas of Illinois. Results from these surveys have revealed alarming trends that threaten the production and sustainability of our current cropping systems in Illinois and elsewhere; namely, that multiple herbicide resistance is increasing in both individuals and populations, and amaranth weeds with previously allopatric distributions are now co-occurring in many locations. This scenario raises concerns not only for weed management, but also over the possible evolutionary course for these species with regards to hybridization, gene flow, and the continued evolution of herbicide resistance.
|Effective start/end date||8/1/10 → 9/30/19|
- National Science Foundation: $553,000.00