Production of unbolting lines through gamma-ray irradiation mutagenesis in genetically modified herbicide-tolerant Zoysia japonica

Abstract

We have developed a genetically engineered herbicide-tolerant Zoysia grass with potential commercial value. However, the possible flow of genes to wild-type or neighboring plant species raises ecological and commercial concerns, although herbicide-tolerant GM Zoysia grass does not appear to pose a significant risk. One efficient way to prevent transgene escape in GM plants is to control fertility. Thus, we attempted to generate GM Zoysia mutants with defects in the development of reproductive organs, but that can be vegetatively propagated. To induce mutation, a range of γ-rays from 10 to 50 Gy, initially determined to be the optimal dose for inducing mutation, was used to irradiate GM Zoysia during the pollination stage. Notably, nine (4%) lines displayed defects in the floral transition from the vegetative to reproductive phase, while all nonirradiated GM Zoysia grasses developed normally. Under greenhouse conditions (natural light and temperature), these GM Zoysia lines have been vegetatively propagated for four years without forming reproductive structures. This technology could also be applied in other GM plants being cultivated through vegetative propagation, such as creeping bent grass.