Bromoxynil, tolerance

February 2002 however, Bayer CropScience, the OXY 235 transgene patent holder at that time, decided to withdraw bromoxynil-tolerant double-low rapeseed (canola) and rapeseed from the Canadian market in April 2002. As a consequence, bromoxynil-tolerant HEAR cultivars were not commercialized in Canada. 

Tolerance to the herbicide bromoxynil, resistance to certain lepidopteran insects... 

Canada cultivates 90% of the canola acres in North America and is the focus of this survey. The three primary commercial herbicide resistant traits in canola are glyphosate resistance (Roundup Ready , RR), glufosinate resistance (Liberty Link , LL), and imidazolinone resistance (Clearfield , CF). There are two other herbicide resistant traits that are used on a relatively small number of acres and these are bromoxynil resistance (BXN ) and triazine tolerance (TT). In 2004, herbicide resistant traits were grown on over 90% of the 12-13 million total canola acres in Canada (Fig. 6.1.5) [7, 8]. 

Another method of increasing resistance to a PSII herbicide is to promote the breakdown of the molecule within the plant before it reaches the active site. This has been achieved in an effective way in the case of bromoxynil resistance in tobacco. Bromoxynil is broken down by a nitrilase enzyme to ammonia and a herbicidally inactive benzoic acid moiety (Figure 1.6). A strain of Klebsiella pneumoniae has been isolated which uses bromoxynil as a primary nitrogen source by virtue of its nitrilase activity. The gene has been characterized and transferred into tobacco using conventional gene transfer techniques. The transgenic tobacco thus produced was able to tolerate more than 20 times the normally lethal dose of bromoxynil. ... 

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