HERBICIDE TOLERANCE (HT)

HERBICIDE TOLERANCE (HT) - Potentially in next 5 years we may see some HT wheat systems that may be introduced into western Canada. Cyanamid plans to introduce an imidazolinone herbicide tolerant (HT) wheat in 2001. This HT variety although classified as a plant with a novel trait (PNT) was made through the use of chemical mutagenesis and not specifically genetic engineering. Monsanto may launch a Roundup Ready®/glyphosate tolerant wheat in 2004 and Novartis, an Acuron gene/PPO herbicide tolerant wheat sometime after 2003.
As example of a HT GM trait: Roundup Ready® TM genes are a bacterial derived version of a plant enzyme. The enzyme is part of a pathway for the production of aromatic amino acids phenylalanine, tyrosine and tryptophan. The gene is ubiquitous. The plant version is sensitive to glyphosate and the bacterial version tolerant to glyphosate. An additional bacterial derived enzyme was transferred to the crop to enhance the degradation of glyphosate . To reduce the chance of the HT gene being spread to wild relatives researchers are attempting to insert HT genes into the chloroplasts.