Interspecific hybridization transfers a previously unknown glyphosate resistance mechanism in Amaranthus species

A previously unknown glyphosate resistance mechanism, amplification of the 5-enolpyruvyl shikimate-3-phosphate synthase (EPSPS) gene, was recently reported in Amaranthus palmeri. This evolved mechanism could introgress to other weedy Amaranthus species through interspecific hybridization, representing an avenue for acquisition of a novel adaptive trait. The objective of this study was to evaluate the potential for this glyphosate resistance trait to transfer via pollen from A. palmeri to five other weedy Amaranthus species (A. hybridus, A. powellii, A. retroflexus, A. spinosus, and A. tuberculatus). Field and greenhouse crosses were conducted using glyphosate-resistant male A. palmeri as pollen donors and the other Amaranthus species as pollen recipients. Hybridization between A. palmeri and A. spinosus occurred with frequencies in the field studies ranging from <0.01% to 0.4%, and 1.4% in greenhouse crosses. A majority of the A. spinosus x A. palmeri hybrids grown to flowering were ...