Submitted to: Weed Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/6/2007
Publication Date: 5/1/2008
Citation: Gaines, T.A., Henry, W.B., Byrne, P.F., Westra, P., Nissen, S.J., Shaner, D.L. 2008. Jointed goatgrass (Aegilops cylindrica) by imidazolinone-resistant wheat hybridization under field conditions. Weed Science. 56:32-36. Interpretive Summary: The purpose of this study was to determine if genes from herbicide tolerant wheat move from wheat into the weed jointed goatgrass. If jointed goatgrass were to incorporate these herbicide resistance genes from wheat, it would make the weed even more difficult to kill. In-crop management options for the farmer would be limited. Jointed goatgrass was sampled side-by-side with the herbicide-resistant wheat and at distances up to 53 m away in both experimental plots and at commercial field study sites in 2003, 2004, and 2005. The jointed goatgrass seeds collected each year were screened in the greenhouse by spraying the herbicide, imazamox. If the weed seeds hybridized with the herbicide resistant wheat, the result was a unique tillering effect in response to the imazamox herbicide application. Hybrid weed seeds were identified in weeds that were growing side by side with the herbicide resistant wheat. Frequency of these seeds ranged from 0.1 to 1.6%. The greatest distance over which hybridization was documented was 16 m.
Technical Abstract: Gene flow between jointed goatgrass and winter wheat is a concern because transfer of herbicide resistance genes from imidazolinone-resistant (IR) winter wheat cultivars to jointed goatgrass could restrict weed management options for this serious weed of winter wheat cropping systems. The objectives of this study were (1) to investigate the frequency of interspecific hybridization between IR wheat and jointed goatgrass in eastern Colorado, and (2) determine the gene action of the IR acetolactate synthase (ALS) allele in IR wheat by jointed goatgrass and IR wheat by imidazolinone-susceptible (IS) wheat backgrounds. Jointed goatgrass was sampled side-by-side with IR wheat and at distances up to 53 m away in both experimental plots and at commercial field study sites in 2003, 2004, and 2005. A greenhouse screening method was used to identify IR hybrids in collected jointed goatgrass seed. The average percent hybridization across sites and years when IR wheat and jointed goatgrass were grown side-by-side was 0.1% and the maximum was 1.6%. The greatest distance over which hybridization was documented was 16 m. The mutant ALS allele contributed 25% of untreated ALS activity in jointed goatgrass by IR wheat F1 plants, as measured by an in vitro ALS assay. The hybridization rate between jointed goatgrass and expression of the IR wheat ALS allele in hybrid plants will both influence trait introgression into jointed goatgrass.