Amaranthus palmeri S. Watson reproduction system: Implications for distribution and management strategies

Amaranthus palmeri S. Watson is one of the most troublesome weed species worldwide, and is considered one of the most devastating weeds in agricultural fields in the United States. Recently, A. palmeri populations have spread beyond their native range, into the Mediterranean region, and have been reported in several European countries. Resistance to 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) and acetolactate synthase (ALS) inhibitors have been found in European populations, exacerbating the management problems with this species in the Mediterranean region. While the biology, ecology, herbicide resistance mechanisms, and agricultural significance of A. palmeri have been studied, there remains a need to discuss how A. palmeri's unique reproductive traits influence its ability to adapt to various environments, especially as an invasive species spreading into new habitats. We review how the genetic and genomic characteristics of A. palmeri interact with aspects of its reproductive biology, including its breeding system, and alter its ability to hybridize and develop herbicide resistance. Finally, we discuss the breeding system of A. palmeri in the context of weed management, and explore different approaches such as irradiated pollens, genetic manipulations, and RNA interference (RNAi).