We present our work on the development of genetically engineered turfgrass varieties with high commercial values. We will discuss the current results of field tests and environment risk assessments. We developed the genetically engineered and commercially viable turfgrass varieties by introducing useful genes into creeping bentgrass and zoysiagrass through Agrobacterium-mediated transformation. We have successfully produced herbicide-, shade- and stress-tolerant, senescence-delayed, and lateral inducement turfgrass varieties. The selection of regenerating callus and the conditions of Agrobacterium infection were an important factor for the highly efficient transformation to insert the genes by Agrobacterium-mediated protocol. Expression of the integrated gene was well stabilized in the regenerated transgenic turf grasses and evidence of efficient transformation was obtained by molecular analysis and herbicide trial.
In the second part of presentation, the environmental risk assessment of transgenic herbicide-tolerant zoysiagrass will be discussed in terms of stable characteristics of the integrated gene. Commercialization of genetically modified (GM) plants requires the assessment of risks associated with the release of GM plants including a detailed risk assessment of their impacts in human health and on the environment. In these assessments, substantial equivalence, cross fertilization, gene flow, occurrence of allergy, studies of non-target biota, and risk management in the test fields for environmental safety were evaluated for wild-type (WT) and GM herbicide-tolerant zoysiagrass for comparison. Non-selective herbicides without glufosinate efficiently eliminated the herbicide-tolerant zoysiagrass for the risk management work. The herbicide-tolerant zoysiagrass in outdoor environment had difficulty of growing healthy because of domineering weeds and grass pathogens. When glufosiante was not applied, there were no advantages for the herbicide-tolerant Zoysia grass to grow.
In the final part of our presentation, we discuss the risk management of GM zoysiagrass based on irradiation breeding technology. One efficient way to prevent the escape of transgenes in GM zoysiagrass is to control its fertility. Thus, we attempted to generate GM zoysiagrass mutants with defects in the development of reproductive organs, which can still be vegetatively propagated. To induce mutation we irradiated GM zoysiagrass during the pollination stage. Under greenhouse conditions (natural light and temperature), the male-sterile GM zoysiagrass mutants have been vegetatively propagated for four years without normal pollen grains. This technology can be applied to other GM plants cultivated through vegetative propagation.