Jointed goatgrass (Aegilops cylindrica Host) is an allotetraploid. ‘Allo‘ means that each set of chromosomes was derived from a different species to form one. Therefore jointed goatgrass is a hybrid that evolved from two other Aegilops parents. ‘Tetraploid‘ indicates that the plant contains 4 sets of chromosomes. Jointed goatgrass contains 28 chromosomes total. The genomes are referred to as C and D.
Winter wheat is an allohexaploid, possessing 6 sets of chromosomes with a total of 42 chromosomes. Wheat contains genomes from two other species compared to JGG. The A and B are derived from Durum and the D from T. tauschii. The similarities in the D genomes in wheat and jointed goatgrass are why there is a chance of outcrossing. If wheat and jointed goatgrass hybridize, the D genomes will complement each other and a hybrid will occur. Originally, scientists thought these hybrids did not contain the necessary fertility genes due to the differences between wheat and jointed goatgrass and were rendered sterile. However, research conducted by Dr. Carol Mallory Smith, Oregon State University, and Dr. Robert Zemetra, University of Idaho, determined that crossing wheat and jointed goatgrass can produce hybrid seed that is approximately 1.5% fertile.
The possibility of hybrids forming creates a new concern. Herbicide resistant wheat varieties bred to allow selective jointed goatgrass control with a herbicide were released in the spring of 2002. The concern of this group is that this technology is in jeopardy already due to the concerns of the resistance gene migrating into a jointed goatgrass population. However, proper management of the technology and further research on the transferring resistance to a jointed goatgrass population is being conducted in many states.