Gene Flow and Hybridization Between Joined Goatgrass (Aegilops cylindrica) and Wheat (Triticum aestivum)
The possibility of gene flow between cultivated species and their wild relatives is a major concern, especially in transgenic crop systems. In the Midwestern and Western United States jointed goatgrass (CD genomes) is a major weed of winter bread wheat (ABD genomes). Weed control, particularly selective herbicide treatment, is difficult because wheat and jointed goatgrass are closely related. Transgenic wheat with herbicide-resistance genes offers a promising control method. Because these two species share the D genome, development strategies for transgenic wheat are focusing on the A and B genomes. Traditionally, hybrids between wheat and jointed goatgrass were believed to be sterile, but partially fertile hybrids and backcross derivatives have been found under field conditions in the USA and have been reproduced under greenhouse conditions. Thus, various projects are currently underway to determine the extent of gene flow and hybridization between jointed goatgrass and wheat. This project involves researchers at the University of Idaho (Drs. R. S. Zemetra) and Oregon State University (Drs. C. Mallory-Smith and O.Riera-Lizarazu).
Gandhi, H., C.A. Mallory-Smith, L.A. Morrison, C.J.W. Watson, M.I. Vales, R.S. Zemetra, and O. Riera-Lizarazu. 2006. Hybridization between wheat and jointed goatgrass (Aegilops cylindrica) under field conditions. Weed Science 54:1073-1079.
Perez-Jones, A. C.A. Mallory-Smith, O. Riera-Lizarazu, C.J.W Watson, Z. Wang, M. Rehmans, and R.S. Zemetra. 2006. Introgression of a strawbreaker foot rot (Pseudocercosporella herpotrichoides) resistance gene from winter wheat (Triticum aestivum) into jointed goatgrass (Aegilops cylindrica). Crop Science 46:2155-2160.
Kroiss, L.J., P. Tempalli, J.L. Hansen, M.I. Vales, O. Riera-Lizarazu, R.S. Zemetra, and C.A. Mallory-Smith. 2004. Marker-assessed retention of wheat chromatin in wheat (Triticum aestivum) by jointed goatgrass (Aegilops cylindrica) backcross hybrids. Crop Science 44: 1429-1433.
Morrison, L.A., O. Riera-Lizarazu, L. Cremieux, and C.A. Mallory-Smith. 2002. Jointed goatgrass (Aegilops cylindrica Host) x wheat (Triticum aestivum L.) hybrids: hybridization dynamics in Oregon wheat fields. Crop Science 42:1863-1872.
Joined Goatgrass (Aegilops cylindrica) Genetic Diversity
Aegilops cylindrica Host (2n=4x=28; genome CCDD) is an allotetraploid formed by hybridization between the diploid species Ae. tauschii Coss. (2n=2x=14; genome DD) and Ae. markgrafii (Greuter) Hammer (2n=2x=14; genome CC). This species is of worldwide economic importance for various reasons. First, jointed goatgrass is a widespread weed of bread wheat, chronically infesting fields in the Midwestern and Western United States as well as fields in the Middle East and parts of Europe. Second, hybridization between jointed goatgrass and wheat and partial female fertility of the resulting naturally-produced hybrids suggest the possibility of crop-to-weed gene movement. Third, jointed goatgrass also has been identified as a source of useful genetic variation for wheat improvement. Therefore, there is considerable interest in understanding patterns of genetic variation and various aspects of the evolution of Ae. cylindrica for its better management and use. Previous research has shown that Ae. tauschii contributed its cytoplasm to Ae. cylindrica. However, our analysis with chloroplast microsatellite markers has shown that Ae. markgrafii has also contributed its cytoplasm to Ae. cylindrica. Our analysis of chloroplast and nuclear microsatellite markers also suggests that D-type plastome and the D genome in Ae. cylindrica were closely related to and were probably derived from the tauschii gene pool of Ae. tauschii. A determination of the likely source of the C genome and the C-type plastome in Ae. cylindrica has not been determined.
Gandhi, H., M.I. Vales, C.J.W. Watson, C.A. Mallory-Smith, N. Mori, M. Rehman, R.S. Zemetra, and O. Riera-Lizarazu. 2005. Chloroplast and nuclear microsatellite analysis of Aegilops cylindrica. Theor. Appl. Genet. 111: 561–572.