Two types of GE contamination in destroyed corn crops

1.00pm

Tests on the parent seedlines of 30 tonnes of maize which was destroyed because it was contaminated with genetically engineered seed have revealed two types of GE strains.

Government officials said today it was likely that GE seeds in the imported parent lines were missed in testing by the seed companies involved because of the relatively small amounts of contaminated seed present.

GE maize seed was accidentally produced after Australian company Pacific Seeds Pty Ltd imported "parent" lines of seed from the United States to produce three hybrid lines of maize to be sold for growing stockfood.

At Gisborne, about nine tonnes of seed was hybridised on a planting of 7ha by Corson Grain. The parent seed lines from the Iowa-based Garst Seed Co were checked for GE content and no engineered gene sequences were detected.

At Pukekohe, two parent lines -- different from the Gisborne crop -- were imported from Missouri-based Monsanto Co, which said it tested them in St Louis before export, and that no engineered sequences were detected.

But after harvest, samples from both the Gisborne and Pukekohe crops tested positive for DNA sequences from a cauliflower mosaic virus "promoter" used widely in GE maize, and further tests showed one of the hybrid lines contained DNA sequences characteristic of the GE maize Bt176 (produced by Syngenta/Novartis) while the other contained DNA sequences characteristic of the GE maize Yieldgard -- both of which were engineered to kill corn borer which fed on the plants.

Pacific Seeds agreed to the destruction in August of approximately 30 tonnes of seed from the contaminated maize crops, and the Ministry of Agriculture and Forestry (MAF) sent seeds remaining from the parent lines at both Pukekohe and Gisborne to the United States for further testing.

The tests have shown the Gisborne female parent seed contained the GE variety Yieldgard and probably Bt176 as well.

Yieldgard and Bt176 are GE maize varieties resistant to corn-borer insects.

MAF said today that although the Gisborne female lines contained very small concentrations of GE seed, the removal of their tassels -- normal practice for hybrid seed production -- meant they were unable to produce pollen.

At Pukekohe, GE seed was detected in both male and female parent seedlines.

The female seed contained Libertylink.

The variety in the male seed was not identified but it is suspected to be a YieldGard variety. Libertylink is a variety resistant to the herbicide Liberty.

Compulsory testing of imported sweetcorn seed imports was introduced by MAF 14 months ago, and only in August this year was it extended to maize seeds.

The seed that produced the contaminated crop was imported in July and August 2001.

Industry sources outside MAF said that in January 2001, Pioneer Hi-Bred International Inc, a unit of DuPont Co, announced that in the United States it would postpone sales of Pioneer Brand corn hybrids that contained a combination of the Yieldgard gene and the Libertylink gene.

The sales were postponed because the hybrids had not been approved to export to the European Union. Hybrids containing the two genes separately had been approved, but not those containing them in combination.

Last year, Pacific Seeds had about 10 per cent of the maize seed market in New Zealand, and had contract growers hybridise the crop from seed imported from Monsanto and from Garst Seed. If it had been distributed it was likely to have been used to grow maize crops this spring for feeding dairy cattle.

Pacific Seeds said parent seed lines from the Iowa-based Garst Seed were checked for GE content by a Melbourne laboratory, GeneScan, using the methods set down by MAF for sweetcorn seed, a sample of 1400 seed. No engineered gene sequences were detected.

At Pukekohe, two parent lines -- different from the Gisborne crop -- were imported from Missouri-based Monsanto, which said it tested them in St Louis before export, and it also said no engineered sequences were detected.

But today MAF said the most likely source of GE maize in the 30 tonne seed harvest was from very small concentrations of GE seed in the imported parent seeds.

GE seed was detected in samples from the Pukekohe hybrid crop taken by Pacific Seeds but was not detected in samples of the crop taken by MAF. The likelihood of detecting GE seed in a line using a sample of 3200 seeds at a GE seed concentration of 0.04 per cent was 71 per cent.

No GE seed was detected in the male parent seed grown at Gisborne, meaning that there was no risk of GE cross-pollination from fields on which this seed was grown.

MAF said in a statement that it was most unlikely that the affected crops pollinated nearby fields containing maize or sweet corn crops.

Although both male and female parents at Pukekohe contained "a minute concentration of GE seed", the fields in which they were grown were well separated from other fields of maize or sweet corn in the area.

"All but one of these nearby crops also flowered at a time when they would not have been receptive to pollen from the affected maize," MAF said.

The concentrations of GE seed in the crops was very small -- less than 0.05 per cent or one in 2000 seeds in the Gisborne samples and probably even smaller than that in the Pukekohe samples.

"Of the approximately 1.8 million maize plants grown in these fields, probably fewer than 800 contained GE material," it said.

- NZPA

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