Borage (Borago officinalis) is an annual herb that produces a high level of
gamma-linolenic acid (GLA) in its seed. Due to the recognized health
benefits of GLA, borage is now commercially cultivated worldwide. However,
an [www.isaaa.org]
herbicide tolerant variety for effective weed management has not yet been
developed. The team of Dongyan Song from the University of Saskatchewan in
Canada developed mutant borage lines tolerant to the herbicide
imidazolinone.

The team used ethyl methanesulfonate (EMS), a substance capable of producing
random mutations, on mature borage seeds to produce a mutant population. The
population was then screened using an herbicide treatment and two
imidazolinone-tolerant lines were identified. Analysis of the two
acetohydroxyacid synthase (AHAS) genes, AHAS1 and AHAS2, in the mutant
(tolerant) and wild type (susceptible) borage plants showed that single
nucleotide substitutions occurred in both genes in the two tolerant lines.

A marker was also developed to differentiate the homozygous susceptible,
homozygous tolerant and heterozygous borage plants. A final herbicide dose
response test indicated that lines with the AHAS1 mutation could tolerate
four times the normally used field concentration of imidazolinone herbicide.

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