ABSTRACTThe ability of the weedy species jointed goatgrass (Aegilops cylindrica Host) to form seedbearing hybrids with wheat (Triticum aestivum L.) raises questions concerning the potential movement of herbicideresistance genes from commercial wheat cultivars into the weed population. As a preliminary step for future geneflow risk assessments, a study of jointed goatgrass wheat hybrids collected from infested wheat fields in 1998 and 1999 was undertaken in Oregon. Jointed goatgrass accessions representing the range of variation in its worldwide distribution also were included in this study. The high molecular weight (HMW) glutenins, a group of wheat endosperm storage proteins, were used as genetic markers for characterizing this material. In the Oregon jointed goatgrass accessions, the seed protein analysis identified F1 hybrid seed that was formed at a rate of 0 to 8% on a per field basis. The HMW glutenin patterns in the backcross seed threshed from Oregon hybrids showed a higher proportion of seeds formed from pollination by wheat than by jointed goatgrass. Analysis of the roots for remains of the maternal seed or spikelet indicated that most hybrid plants were of the F1 generation and that either jointed goatgrass or wheat could be the female parent. These analyses suggested a hybridization dynamics in which jointed goatgrass serves as the predominant F1 female parent and wheat as the predominant backcross male parent. Development of introgressed jointed goatgrass forms carrying wheat genes would be dependent on the presence of a continuous hybrid zone located near or within a persistent jointed goatgrass population.
