Winter annual grass control and crop safety in quizalofop-resistant wheat cultivars.
Winter annual grass species such as jointed goatgrass (Aegilops cylindrica Host), downy brome (Bromus tectorum L.), and feral rye (Secale cereale L.) negatively affect winter wheat (Triticum aestivum L.) yields. To generate a novel in-crop selective herbicide trait for winter annual grass control, mutagenesis was used to generate multiple winter wheat lines resistant to the acetyl co-A carboxylase (ACCase) inhibitor quizalofop p-ethyl (QPE). Field trials were performed to assess crop safety for wheat lines with one or two homoeologous mutations and to assess winter annual grass control with QPE treatments. Crop safety parameters including visual injury rating, plant height, grain yield, and kernel weight were evaluated following QPE treatment at multiple growth stages. The susceptible winter wheat cultivar Hatcher displayed 100% crop injury when treated at tillering in early spring or at jointing in late spring. Single-gene lines generally had crop injury and yield loss, especially at the jointing application timing. The two-mutation cultivars Incline AX and LCS Fusion AX had low to no injury or yield loss from QPE applications at all timings and no injury from high rate QPE applications (93 and 185 g ha-1) in either the fall or the spring. Control of downy brome and feral rye was highest (92-99%), while jointed goatgrass control ranged from a low of 73% at 93 g a.i. ha-1 to a high of 98% at 109 a.i. ha-1 QPE. Our data indicate that the targeted winter annual grass weeds are controlled by QPE at rates that have acceptable crop safety for two-mutation QPE-resistant wheat cultivars.