Gene Flow Between Wheat and Jointed Goatgrass: Occurrence Vs. Risk.

Gene flow and production of hybrids between wheat (Triticum aestivum L.) and jointed goatgrass (Aegilops cylindrica Host.) are well documented.  F₁ hybrids are male sterile with low female fertility.  However, seed production increases each backcross generation increasing the potential for gene spread.  The widespread production of the imidazolinone-resistant Clearfield^® wheat (imi- wheat) provided an excellent opportunity to study gene flow between wheat and jointed goatgrass.  In an Oregon survey of fields with a history of imi-wheat production, 1100 of 1400 plants sampled carried the Imi1 gene which endows imidazolinone resistance.  Thirteen of the plants were homozygous for the gene indicating that the gene had moved beyond the first generation.  The consequences of moving a gene from wheat to jointed goatgrass will depend on the trait’s impact on the invasiveness and spread of the weed.  Jointed goatgrass evolved with wheat domestication and production.  Although jointed goatgrass occurs outside of cultivation, in the United States it is generally associated with agriculture.  Herbicide resistance remains largely an agronomic issue but stress tolerance traits could increase the invasiveness of jointed goatgrass and expand its range.  Thus, traits need to be evaluated on a case-by-case basis.  Gene flow via seed movement must be considered and may provide a greater avenue and risk potential for gene movement than pollen does.  Gene flow cannot be prevented in natural or agricultural environments; however, there are steps that can be taken to reduce movement especially in agricultural settings.