Dow hopes to test new insect-resistant cotton lines

The prospect of Australia's cotton industry returning to the continent's well-watered tropics has enticed a new player to test its transgenic wares against the insect monsters that ate the Ord.

The Australian division of multinational Dow AgroSciences has applied to the Office of the Gene Technology Regulator to conduct expanded field trials of three experimental transgenic cotton lines carrying genes for insecticidal proteins to kill caterpillars of the two major native pests of cotton the heliothine moths Helicoverpa armigera and H. punctigera.

Dow AgroSciences has already conducted a tiny field trial -- only 400 square metres -- of three of its proprietary Widestrike cotton lines, which contain two transgenes for insecticidal delta endotoxins from the common soil bacterium Bacillus thuringiensis (Bt), plus a third transgene conferring tolerance to the herbicide glufosinate ammonium (Syngenta's Basta).

The company's regulatory affairs officer, Dr Matt Cahill, said the glufosinate tolerance gene was used as a selectable marker when the plants were developed, and would not be covered by the commercial licence if and when the transgenic cottons entered commercial production.

One of the insecticidal transgenes being trialled is Dow's own version of the Cry1Ac gene already used in first generation Ingard transgenic cotton cultivars, developed by CSIRO and Deltapine, and their newly released twin-gene Bollgard 2 successors. Both types use the Monsanto version of the Cry1Ac gene.

Dow has paired Cry1AC with its own Cry1F endotoxin gene, which, while new to Australia, has proved highly effective against the major pests of US cotton and several other horticultural crops. Cahill said Widestrike cultivars showed broad-spectrum resistance to cotton bollworm, pink bollworm, tobacco budworm, beet army worm, fall army worm, and looper caterpillars.

Dow acquired a huge library of Bt endotoxin genes by acquiring US biotech company Mycogen, and is now working to develop commercial applications.

The company has applied to the OGTR to trial the Widestrike lines on 25 sites, totaling 10 hectares, over four growing seasons -- two summer, two winter -- in NSW, Queensland, the Northern Territory and Western Australia.

Cahill described the trials as "really just the fist bite of the cherry", to see how well Dow's double-whammy gene combination works against Australian heliothine pests.

Even if the tests are successful, Cahill said, the genes would then have to be introduced into cotton varieties bred for Australian conditions, and Dow AgroSciences would have to find a commercial partner to develop commercial cultivars.