Field Trial Study of Transgenic Creeping Bentgrass (Agrostis stolonifera L.) Plants Expressing An Arabidopsis H+-Pyrophosphatase.

The transgenic perennial creeping bentgrass plants overexpressing Arabidopsis vacuolar H⁺-pyrophosphatase (AVP1) exhibited improved resistance to salinity in the controlled growth room conditions. To further evaluate the improved salt resistance in natural conditions, a two-year field trial study under the USDA-APHIS permit was conducted, in which twenty five one-square-foot plots for both the wild type and transgenic plants were randomly arranged in five treatments (0, 366, 732, 1098 and 1464 grams of NaCl input m^-2, respectively) with five replicates in each treatment. After one year of regular maintenance of the plant materials in the field to ensure their full development, the transgenic and wild type plants were used for salt stress treatment experiments from the fall of 2010 to the spring of 2011 with the field plots established in October 2009. Preliminary data obtained demonstrate enhanced performance of transgenic plants, which is associated with the higher relative water content, and lower solute leakage in leaf tissues. The proline content was increased in both wild-type and transgenic plants, but significant differences were observed between wild-type and transgenic plants in tissues collected under the higher salt stress (1098 and 1464 grams m^-2 NaCl). Moreover, transgenic plants exhibited higher photosynthesis efficiency than wild-type controls during the summer months. The soil volumetric water contents (VWC) and electronic conductivities were also measured and no differences between the treatments with the same NaCl input were observed. Our results demonstrate that the performance of AVP1-expressing transgenic plants in the field trial is in agreement with the observations under greenhouse conditions and indicate that the transgenic creeping bentgrass can be developed into new cultivars for commercialization with improved salinity and other stress tolerances.