POOR farmers could soon be growing genetically modified plants from home-grown seeds. The plants have been designed to produce fertile seed that carry desirable new traits, but will be incapable of spreading their alien genes into the environment. This is a crucial feature that could herald a new era in GM crops.
Environmentalists have long warned about the dangers of GM plants transmitting new traits to other plants. Genes intended to make crop plants resistant to weedkillers have already spread to other crops on farms, notably in Canada. To avoid this, biotech companies proposed making their GM crops sterile, using so-called 鈥渢erminator鈥� technology. But the idea simply raised another problem: poorer farmers would no longer be able to save seeds from one harvest to sow the following year. The resulting outcry forced biotech companies to abandon terminator technology.
Now it is back on the agenda in the shape of a tobacco plant that can self-pollinate and produce viable seeds but cannot reproduce with any other plants. 鈥淚t鈥檚 a trick to keep a seed line genetically pure yet stop the GM trait escaping,鈥� says Johann Schernthaner of the Canadian team that devised the patented system, dubbed Geneguard. The work was done at the Eastern Cereal and Oilseed Research Centre in Ottawa, part of Canada鈥檚 agriculture ministry.
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The modified tobacco contains two extra genes in addition to those added to provide a beneficial trait such as disease resistance. Both originate in bacteria. The first, from the soil-dwelling Agrobacterium tumefaciens, inhibits seed germination. This gene is directly linked to the DNA that confers the beneficial trait, so any seeds with just these added genes cannot germinate.
The second bacterial gene, from E. coli, blocks the action of the first one. 鈥淚ts protein simply sits on the first gene and prevents it working,鈥� says Schernthaner. With both genes present, germination proceeds normally and the seeds can grow into mature GM plants and self-pollinate, generation after generation. 鈥淎s long as the plant fertilises itself, it can be maintained forever,鈥� he says.
The key feature of Geneguard is that the two bacterial genes separate when the plant makes pollen. This means that if the GM pollen fertilises a wild plant or conventional tobacco, any resulting seeds with the disease-resistance trait will also have the germination blocker. They may inherit the second bacterial gene instead, but by itself this is innocuous (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1036833100).
The researchers have not yet perfected the Geneguard system, because they cannot guarantee that the beneficial trait will not escape. The two bacterial genes have to be inserted separately into the chromosomes of two parent plants, which are then bred together to produce offspring carrying both genes. To ensure that the genes separate during pollen formation in the GM tobacco, they must be inserted into exactly the same position on both parent plants鈥� chromosomes. The Canadian team has not yet achieved this. But Schernthaner points out that it may be possible through a technique called site-specific insertion. Other agriculture ministry researchers, based in Saskatoon, Saskatchewan, are trying to use the technology in oilseed rape.
But ETC Group, a lobby organisation critical of GM technology based in Winnipeg, Manitoba, is not convinced of Geneguard鈥檚 benefits. 鈥淚t鈥檚 bad news for farmers,鈥� says ETC鈥檚 research director, Hope Shand. Poor farmers will not be able to breed their own varieties from their saved seeds, she points out.
鈥淚f this technique works, it might reduce industry鈥檚 risk from GM contamination,鈥� she concedes. But she thinks the price is too high: 鈥淭he loss of breeding capacity is an unacceptable trade-off.鈥� But Schernthaner says poor farmers seldom have the means to develop their own varieties.
