Herbicide tolerant crops provide farmers access to a new weed control option of nonselective herbicide such as Roundup1 A wheat transgenic event 33391 was produced via Agrobacterium‐mediated transformation of a donor cultivar Bobwhite wheat (Triticum aestivum L.) and was identified as a commercial candidate to develop Roundup Ready wheat2 The objective of this study was to assess field efficacy of the transgenic event in spring wheat production regions in North America. Transgenic event 33391 was tested in field trials at 14 locations in 1999, 13 locations in 2000, and 14 locations in 2001. All trials were split‐plot designs with multiple rates of Roundup treatment. No vegetative or reproductive damage was observed with the application of 4 L ha−1 Roundup at the 3‐ to 5‐leaf stages. No yield reduction was observed with Roundup treatment. The transgenic event with or without Roundup application yielded as high as the nontransgenic Bobwhite. These results indicate that the wheat transgenic event 33391 has at least 2× tolerance to the nonselective herbicide Roundup.

The launch of commercially available Roundup Ready (RR) soybean [Glycine max (L.) Merr.] cultivars in 1996 initiated a new era in agricultural weed management. Efforts with the goal of creating commercially available hard red spring wheat (Triticum aestivum L.; HRSW) cultivars were initiated between Monsanto and three HRSW breeding programs located in the North Central Plains of United States. A backcross (BC) breeding scheme was initiated to introgress the RR trait into four previously released HRSW cultivars with the ultimate goal of offering a novel and cost‐effective weed management option to growers through the application of Roundup herbicide directly over established RR HRSW cultivars. Agronomic field tests were performed in 2002 and 2003 with 12 transgenic backcross‐derived (BCD) RR HRSW breeding lines and four recurrent parent (RP) cultivars in North Dakota, South Dakota, and Minnesota. Grain yield, grain volume weight, and days to heading among the RR HRSW lines were largely similar to their respective RP cultivars. However, plant lodging scores were often significantly lower among the BCD‐RR lines compared to the conventional cultivars.