Field Trial of Transgenic Creeping Bentgrass in Competition with Alfalfa and Annual Bluegrass.

A field trial has been conducted to evaluate transgene impact on interspecific competition, assessing interaction of creeping bentgrass with either a weed, annual bluegrass or a legume, alfalfa. The competing species, annual bluegrass and alfalfa, were grown together with three transgenic creeping bentgrass lines harboring a rice SUMO E3 ligase gene OsSIZ1, an Arabidopsis vacuolar H⁺-pyrophosphatase gene AVP1 and a cyanobacteria flavodoxin gene Fld, respectively. The plants were arranged in two main factorial field plot design with three replications. Six months after field growth, the growth competition between creeping bentgrass, alfalfa and annual bluegrass as measured by shoot and root biomass was evaluated. Although both shoot and root biomass of the alfalfa competing with the OsSIZ1- or AtAVP1-overexpressing transgenic creeping bentgrass is significantly lower than that of the alfalfa grown alone, there was no significant difference in shoot and root biomass between plants competing with the OsSIZ1- and AtAVP1-overexpressing transgenic creeping bentgrass plants. However, in the Fld-overexpressing creeping bentgrass trial, the root and shoot biomass of alfalfa showed no significant difference compared to none-competing control. There was no significant difference in both root and shoot biomass of annual bluegrass between plants competing with wild type and the transgenics (OsSIZ1 and AtAVP1). In the transgenic creeping bentgrass-annual bluegrass trial, the root and shoot dry weight of annual bluegrass was significantly higher than the other competition combinations. Our data suggest that transgene impact on the growth of non-target plant species is gene-specific and needs to be assessed in a case-by-case manner.