Genetically engineered varieties of creeping bentgrass, resistant to glyphosate, have been developed. Studies were initiated in 2000 and 2001 to examine the relative competitive lateral spread of several transformed lines of creeping bentgrass, nontransformed controls, and cultivar standards. Five-centimeter-diameter vegetative plugs of creeping bentgrass were transplanted into a 1-yr-old stand of perennial ryegrass in Columbus, OH, and 10-yr-old bermudagrass or 10-yr-old St. Augustinegrass in Loxley, AL. Plots were watered to prevent moisture stress to either the bentgrass plugs or surrounding turf swards. Monthly average diameter of the creeping bentgrass was determined by measuring the longest spread and shortest spread. At the end of the experiment, no differences (P = 0.05) in lateral spread were observed between individual lines of transgenic bentgrass, standard cultivars, and nontransformed control lines. Lateral spread of transgenic lines was similar to or less than their nontransformed parent and the standard cultivars tested. Results indicate that glyphosate-resistant creeping bentgrass lines do not spread laterally more than nontransgenic lines. Therefore, if the glyphosate-resistant creeping bentgrass escaped into surrounding turfgrass swards, the potential for spread would not be greater than other creeping bentgrass cultivars currently in use.

Nomenclature: Glyphosate; bermudagrass, Cynodon dactylon L.; creeping bentgrass, Agrostis stolonifera L. syn. Agrostis palustris Huds.; perennial ryegrass, Lolium perenne L.; St. Augustinegrass, Stenotaphrum secondatum S. (Walt.) Kuntze.

Additional index words: Competition, genetically modified organism, GMO.