Hypothesis: Transgene establishment in wild relatives of wheat can be prevented by utilizing the Ph1 gene as a senso stricto chaperon to prevent homoeologous recombination

Durum and bread wheat need transgenic traits such as herbicide and disease resistance due to recent evolution of herbicide resistant grass weeds and an intractable new strain of stein rust. Transgenic wheat varieties have not been commercialized partly due to potential transgene movement to wild/weedy relatives, which occurs naturally to closely related Aegilops and other spp. Recombination does not occur in the F-1 hybrid between wheat and its relatives due to the presence of the Phi gene on wheat chromosome arm 5BL, which acts as a chaperone, preventing promiscuous homoeologous pairing to similar, but not homologous chromosomes of the wild/weedy species. Thus recombination must occur during backcrossing after the wheat Pill gene has been eliminated. Based on these findings, we speculate that Phi could be used to prevent gene introgression into weedy relatives. We propose two methods to prevent such transgene establishment: (I) link the transgene in proximity to the wheat Phi gene and (2) insert the transgene in tandem with the lethal barnase on any chromosome arm other than 5BL, and insert barstar, which suppresses barnase on chromosome arm 5BL in proximity to Phi. The presence of Phi in backcross plants containing 5BL will prevent the homoeologous establishment of barnase coupled to the desired transgene in the wild population. 5BL itself will be eliminated during repeated backcrossing to the wild parent, and progeny bearing the desired transgene in tandem with barnase but without the Ph1-barstar complex will die. (C) 2008 Elsevier Ireland Ltd. All rights reserved.