In-field assessment of <i>EPSPS</i> amplification on fitness cost in mixed glyphosate-resistant and glyphosate-sensitive populations of Palmer amaranth (<i>Amaranthus palmeri</i>)

Abstract Comparing fitness of herbicide-resistant and herbicide-susceptible weed biotypes is important for managing herbicide resistance. Previous research suggests there little to no penalty from amplification the 5-enolpyruvylshikimate-3-phosphate synthase ( EPSPS ) gene (a mechanism glyphosate resistance) in Palmer amaranth Amaranthus palmeri S. Watson) controlled studies greenhouse or growth chamber. A field study was conducted North Carolina at three locations naturally infested with A. determine vegetative, reproductive, germination plants without grown season-long cotton Gossypium hirsutum L.). Seed number not correlated copy number. However, when were binned into two groups, those having an ≥2 (relative reference genes) &lt;2, plant fresh weight seed 1.4 1.6 times greater, respectively, fewer than 2 copies. height germination, yield cotton, did differ comparing groups. These data suggest that are relatively less fit absence glyphosate, but this reduced does translate differences interference cotton.